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  • Polymer and Materials Science  (112,478)
  • Engineering General  (9,884)
  • Insulin
  • Psychopharmacology
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  • 1
    Electronic Resource
    Electronic Resource
    Short-term treatment with GLP-1 increases pulsatile insulin secretion in Type II diabetes with no effect on orderliness (2000)
    Springer
    Diabetologia 43 (2000), S. 583-588 
    Details
    ISSN: 1432-0428
    Keywords: Keywords GLP-1 ; Insulin ; pulsatility ; insulin secretion ; time series ; Type II diabetes ; human.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. The enteric incretin hormone, glucagon-like peptide-1 (GLP-1), is a potent insulin secretagogue in healthy humans and patients with Type II (non-insulin-dependent) diabetes mellitus. In this study we assessed the impact of short-term GLP-1 infusion on pulsatile insulin secretion in Type II diabetic patients. Methods. Type II diabetic patients (n = 8) were studied in a randomised cross-over design. Plasma insulin concentration time series were obtained during basal conditions and during infusion with saline or GLP-1 (1.2 pmol/l · kg–1· min–1) on 2 separate days. Plasma glucose was clamped at the initial concentration by a variable glucose infusion. Serum insulin concentration time series were evaluated by deconvolution analysis, autocorrelation analysis, spectral analysis and approximate entropy. Results. Serum insulin concentrations increased by approximately 100 % during GLP-1 infusion. Pulsatile insulin secretion was increased as measured by secretory burst mass (19.3 ± 3.8 vs 53.0 ± 10.7 pmol/l/pulse, p = 0.02) and secretory burst amplitude (7.7 ± 1.5 vs 21.1 ± 4.3 pmol/l/min, p = 0.02). A similar increase in basal insulin secretion was observed (3.6 ± 0.9 vs 10.2 ± 2.2 pmol/l/min, p = 0.004) with no changes in the fraction of insulin delivered in pulses (0.50 ± 0.06 vs 0.49 ± 0.02, p = 0.84). Regularity of secretion was unchanged as measured by spectral analysis (normalised spectral power: 5.9 ± 0.6 vs 6.3 ± 0.8, p = 0.86), autocorrelation analysis (autocorrelation coefficient: 0.19 ± 0.04 vs 0.18 ± 0.05, p = 0.66) and the approximate entropy statistic (1.48 ± 0.02 vs 1.51 ± 0.02, p = 0.86). Conclusion/interpretation. Short-term stimulation with GLP-1 jointly increases pulsatile and basal insulin secretion, maintaining but not improving system regularity in Type II diabetic patients. [Diabetologia (2000) 43: 583–588]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250051347
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  • 2
    Electronic Resource
    Electronic Resource
    Pharmacodynamics and pharmacokinetics of intravenous glibenclamide in Caucasian and Chinese patients with type-2 diabetes (2000)
    Springer
    European journal of clinical pharmacology 55 (2000), S. 721-727 
    Details
    ISSN: 1432-1041
    Keywords: Key words Glibenclamide ; Insulin ; Proinsulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: We analysed the kinetics and effects of glibenclamide (Gb) on glucose, insulin and proinsulin secretion in two ethnic groups (10 in each) of type-2 diabetic patients, one of Caucasian, the other of Chinese origin. Background: Diabetes mellitus type 2 is a global disease affecting all ethnic groups. There are ethnic differences in both the prevalence and metabolic characteristics of the disease. Important interethnic pharmacodynamic and pharmacokinetic differences have been reported for several drugs. With few exceptions, detailed studies on sulphonylurea are lacking. Material and methods: The patients were studied on two occasions when either no Gb (control) or 1.25 mg Gb was administered i.v., immediately before the administration of a 75-g oral glucose tolerance test. Concentrations of insulin and proinsulin were determined by means of radioimmunoassay without cross-reactivities. Gb concentration was determined using high-performance liquid chromatography. Pharmacodynamic results were calculated using net areas under the curves, with basal values set as zero. A P value less than 0.05 was considered significant. Results: When glucose was administered orally without Gb, Chinese patients had higher plasma glucose increases at 10 min (7.6 mmol/l × min vs 2.6 mmol/l × min) and higher increases of plasma insulin levels than Caucasians at both 10 min (198 pmol/l × min vs 54 pmol/l × min) and 30 min (2286 pmol/l × min vs 1198 pmol/l × min). When Gb was administered, the plasma glucose increases were reduced, and the increases of serum insulin and proinsulin levels were greater in both ethnic groups. Compared with the basal values (−1 min), proinsulin/insulin ratios (RPI) were lowest at 10–30 min, followed by an increase. Chinese patients had higher increases of serum insulin levels at 10 min (1109 pmol/l × min vs 550 pmol/l × min) and a lower RPI at 30 min (6.0% vs 7.6%) and 240 min (15.0% vs 21.0%) relative to Caucasians. Serum Gb data were best fitted to a biexponential i.v. model. There were no interethnic differences in any of the pharmacokinetic parameters. Conclusion: In summary, following oral glucose administration without Gb, Chinese type-2 diabetic patients had higher plasma insulin levels but also higher plasma glucose levels during the first 10 min, which might reflect reduced insulin sensitivity or more rapid glucose absorption. Gb augmented glucose-induced release of both insulin and proinsulin in both ethnic groups; the effect on insulin secretion was more pronounced. In conclusion, minor pharmacodynamic but no pharmacokinetic differences were found between the two groups. It seems appropriate to employ the same dosage principles when using Gb in Caucasians and Chinese.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050004
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  • 3
    Electronic Resource
    Electronic Resource
    Growth, puberty and hypothalamic-pituitary function in children with suprasellar arachnoid cyst (2000)
    Springer
    European journal of pediatrics 159 (2000), S. 348-355 
    Details
    ISSN: 1432-1076
    Keywords: Key words Arachnoid cyst ; Growth ; Growth hormone deficiency ; Growth hormone treatment ; Insulin ; Leptin ; Puberty ; Precocious puberty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A suprasellar arachnoid cyst may cause disorders of growth, puberty and hypothalamic-pituitary function, due to the proximity of the cyst to the hypothalamic-pituitary area. A total of 30 patients (17 boys) with cyst diagnosed at 4.3 ± 1 years were routinely evaluated at 5.4 ± 1 years; 24 of them had one or multiple cyst derivations. Some 23 cases had an abnormal height, weight or puberty: short (〈−2SD, 5 cases) or tall (〉2SD, 10 cases) stature, overweight (body mass index, BMI, 〉2SD, 6 cases), central precocious puberty (10 cases) and/or no progression of pubertal development (3 cases). The growth hormone (GH) peaks after pharmacological stimulation test were low (〈10 μg/l) in 16 patients, confirmed by a second evaluation in 8/11 of them. The plasma free thyroxine was low in five patients, prolactin was high in two and the cortisol and concomitant plasma and urinary osmolalities were normal. BMI was correlated negatively with the GH peaks (r=−0.37, P 〈 0.01) and positively with the plasma leptin concentrations (r=0.55, P 〈 0.01). The plasma fasting insulin concentrations were also correlated negatively with the GH peaks (r=−0.55, P 〈 0.02) and positively with the plasma insulin-like growth factor I concentrations (r=0.64, P 〈 0.002). The adult height (12 cases) was at 4SD in 1 and 〈−2SD in 4 patients, two of whom had precocious puberty untreated with gonadotropin releasing hormone (GnRH) analogue, and two had untreated GH deficiency. The adult height of those treated was normal. One girl had primary amenorrhoea and two boys had low plasma testosterone, despite a normal gonadotropin response to a GnRH test. Conclusion Suprasellar arachnoid cysts may cause deficiencies of growth hormone and thyrotropin, stimulation of the hypothalamic-pituitary-gonadal axis, tall stature and/or overweight. These last two disorders may be due to hyperinsulinism, itself due to suprasellar arachnoid cyst.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004310051285
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  • 4
    Electronic Resource
    Electronic Resource
    IGF and Insulin Action in the Mammary Gland: Lessons from Transgenic and Knockout Models (2000)
    Springer
    Journal of mammary gland biology and neoplasia 5 (2000), S. 19-30 
    Details
    ISSN: 1573-7039
    Keywords: Insulin ; transgenic ; knockout ; mammary ; IGF
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Transgenic and knockout mice have become valuable experimental systems with which tostudy specific molecular events within the mammary gland of an intact animal. These modelshave provided a wealth of information about the effects of a number of oncogenes and growthfactors. This review focuses on results obtained from the application of transgenic and knockoutmodels to determine the roles of insulin and insulin-like growth factors (IGF)3 in the regulationof mammary gland development, lactation and tumorigenesis. Transgenic models whichoverexpress IGF-I or -II display specific alterations in mammary gland development and an increasedincidence of mammary tumors. Analysis of mammary gland development in knockout micewhich are deficient in IGF-I or the IGF-I receptor supports the conclusion that the IGF systemis important for normal mammary gland development. This review discusses these observationsin detail and attempts to fit them into a larger picture of IGF and insulin action in themammary gland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009559014703
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  • 5
    Electronic Resource
    Electronic Resource
    Nitric Oxide, Superoxide, and Peroxynitrite Effects on the Insulin Secretion and Viability of βTC3 Cells (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 102-109 
    Details
    ISSN: 1573-9686
    Keywords: Nitric oxide ; Superoxide ; Pancreatic cells ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The onset of insulin-dependent diabetes mellitus (IDDM) is often associated with the infiltration of pancreatic cells by macrophages. Upon activation, macrophages release nitric oxide (NO) and superoxide (O 2 - ). These species or their reactive intermediates can be cytoxic, mutagenic, or carcinogenic. Previous studies have reported both positive and negative effects of extracellularly generated NO on insulin secretion and viability of pancreatic cells. Inherent problems of several previous studies assessing the effects of NO on insulin secretion include unsteady state NO concentration exposures and the generation of other potentially damaging species. In this study, these problems were eliminated by using a modified experimental system in which NO delivery was achieved via diffusion across a gas-permeable tube and O 2 - delivery was maintained using an enzymatic reaction. The delivery rates were constant, leading to steady state concentrations of NO and O 2 - in the experimental system. Based on reaction kinetics, a model was developed to predict NO, O 2 - and peroxynitrite ONOO- concentrations during the experiment. This study showed that NO, O 2 - and ONOO- at predicted concentrations as high as 2.8 μM, 0.25 μM, and 0.1 nM, respectively, do not affect the insulin secretion rates of βTC3 pancreatic cells over short times. © 2000 Biomedical Engineering Society. PAC00: 8717-d
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.258
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  • 6
    Electronic Resource
    Electronic Resource
    Bayesian Identification of a Population Compartmental Model of C-Peptide Kinetics (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 812-823 
    Details
    ISSN: 1573-9686
    Keywords: C-peptide ; Population model ; Compartmental model ; Bayes estimation ; Markov chain Monte Carlo ; Insulin ; System identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract When models are used to measure or predict physiological variables and parameters in a given individual, the experiments needed are often complex and costly. A valuable solution for improving their cost effectiveness is represented by population models. A widely used population model in insulin secretion studies is the one proposed by Van Cauter et al. (Diabetes 41:368–377, 1992), which determines the parameters of the two compartment model of C-peptide kinetics in a given individual from the knowledge of his/her age, sex, body surface area, and health condition (i.e., normal, obese, diabetic). This population model was identified from the data of a large training set (more than 200 subjects) via a deterministic approach. This approach, while sound in terms of providing a point estimate of C-peptide kinetic parameters in a given individual, does not provide a measure of their precision. In this paper, by employing the same training set of Van Cauter et al., we show that the identification of the population model into a Bayesian framework (by using Markov chain Monte Carlo) allows, at the individual level, the estimation of point values of the C-peptide kinetic parameters together with their precision. A successful application of the methodology is illustrated in the estimation of C-peptide kinetic parameters of seven subjects (not belonging to the training set used for the identification of the population model) for which reference values were available thanks to an independent identification experiment. © 2000 Biomedical Engineering Society. PAC00: 8715Aa, 0250Ga, 8714-g
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.1289459
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  • 7
    Electronic Resource
    Electronic Resource
    Muscle glycogen resynthesis rate in humans after supplementation of drinks containing carbohydrates with low and high molecular masses (2000)
    Springer
    European journal of applied physiology 81 (2000), S. 346-351 
    Details
    ISSN: 1439-6327
    Keywords: Key words Carbohydrate ; Osmolality ; Glycogen ; Insulin ; Glucose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The rate of muscle glycogen synthesis during 2 and 4 h of recovery after depletion by exercise was studied using two energy equivalent carbohydrate drinks, one containing a polyglucoside with a mean molecular mass of 500 000–700 000 (C drink), and one containing monomers and oligomers of glucose with a mean molecular mass of approximately 500 (G drink). The osmolality was 84 and 350 mosmol · l−1, respectively. A group of 13 healthy well-trained men ingested the drinks after glycogen depleting exercise, one drink at each test occasion. The total amount of carbohydrates consumed was 300 g (4.2 g · kg−1) body mass given as 75 g in 500 ml water immediately after exercise and again 30, 60 ad 90-min post exercise. Blood glucose and insulin concentrations were recorded at rest and every 30 min throughout the 4-h recovery period. Muscle biopsies were obtained at the end of exercise and after 2 and 4 h of recovery. Mean muscle glycogen contents after exercise were 52.9 (SD 27.4) mmol glycosyl units · kg−1 (dry mass) in the C group and 58.3 (SD 35.4) mmol glycosyl units · kg−1 (dry mass) in the G group. Mean glycogen synthesis rate was significantly higher during the initial 2 h for the C drink compared to the G drink: 50.2 (SD 13.7) mmol · kg−1 (dry mass) · h−1 in the C group and 29.9 (SD 12.5) mmol · kg−1 (dry mass) · h−1 in the G group. During the last 2 h the mean synthesis rate was 18.8 (SD 33.3) and 23.3 (SD 22.4) mmol · kg−1 (dry mass) · h−1 in the C and G group, respectively (n.s.). Mean blood glucose and insulin concentrations did not differ between the two drinks. Our data indicted that the osmolality of the carbohydrate drink may influence the rate of resynthesis of glycogen in muscle after its depletion by exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050053
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  • 8
    Electronic Resource
    Electronic Resource
    Insulin alters cardiac muscle creatine kinase activity (2000)
    Springer
    Heart and vessels 15 (2000), S. 23-29 
    Details
    ISSN: 1615-2573
    Keywords: Key words Creatine kinase isoenzyme ; Insulin ; Atenolol ; Diabetes mellitus ; Myocardium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The expression of mRNAs of creatine kinase (CK)-B and CK-M has been show to be affected by insulin, and myocardial CK-MB activity is suppressed in insulin-deficient rats. We investigated the dose-related effect of insulin on CK-MB activity in cardiac and skeletal muscles. Male Wistar rats were divided into three groups: (1) control group, (2) diabetic group, injected with 65 mg/kg streptozotocin for 4 weeks, and (3) atenolol group, administered 30 mg/kg per day atenolol. Each group was further divided into three subgroups and administered either saline, or 20 (Ins 20) or 30 (Ins 30) U/kg per day insulin. After 3 weeks, the isoenzyme activity of CK and lactate dehydrogenase (LDH) in the left ventricle of the heart (LV) and the major pectoral muscle (PM) was measured. Serum insulin increased and plasma glucose decreased in Ins 20 and Ins 30, dose-dependently, in all three groups. Both CK-MB and -BB activity in LV increased dose-dependently with insulin treatment in the control, diabetes, and atenolol groups, although these changes did not occur in skeletal muscles. CK-MB in LV correlated with the serum insulin levels in all rats, while no correlation was found in the skeletal muscles. These findings suggest that insulin possibly regulates the distribution of CK isoenzymes in rat heart muscle, and that the effect of insulin is not due to the sympathetic drive induced by hypoglycemia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003800070044
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  • 9
    Electronic Resource
    Electronic Resource
    The autumnal fattening of the long-distance migratory garden warbler (Sylvia borin) is stimulated by intermittent fasting (2000)
    Springer
    Journal of comparative physiology 170 (2000), S. 627-631 
    Details
    ISSN: 1432-136X
    Keywords: Key words Fattening ; Food availability ; Insulin ; Glucagon ; Corticosterone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract To investigate the proximate influence of a changing food availability on the seasonal fattening of migratory birds, garden warblers (Sylvia borin) following postnuptial moult were food restricted once a week. Body mass, food intake, plasma hormone and metabolite levels were measured and compared to birds which always had ad libitum food access. The food-restricted birds increased their body mass significantly earlier than the controls. The accelerated fattening was initially not accompanied by hyperphagia and may be due to either an increased food utilisation efficiency or a reduced metabolic rate. An increase of basal glucagon and corticosterone and a decrease of insulin levels prior to fattening were not significant, however, they resulted in a significant decrease of the insulin:glucagon ratio. This ratio was also lower in food-restricted birds than in control birds and may account for the difference in the fattening progress. We conclude that seasonal fattening may be stimulated by a catabolic impulse which could be imposed in free-living birds by a decrease of food availability and/or by an increase of energy expenditure. A negative energy balance is hypothesised to be a common proximate factor affecting migratory as well as winter fattening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600000143
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  • 10
    Electronic Resource
    Electronic Resource
    Erfassung von Neurotransmitterinteraktionen mit PET und SPECT durch pharmakologische Challenge-Paradigmen (2000)
    Springer
    Der Nervenarzt 71 (2000), S. 9-18 
    Details
    ISSN: 1433-0407
    Keywords: Schlüsselwörter PET ; SPECT ; Neurotransmitter ; Interaktionen ; Psychopharmakologie ; Key words PET ; SPECT ; Neurotransmitter ; Interactions ; Psychopharmacology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Functional brain imaging with positron emission tomography (PET) and single photon emission computerized tomography (SPECT) enables the in vivo study of specific neurochemical processes in the context of normal regulatory mechanisms and pathophysiological alterations of the brain. By combining these methods with pharmacological challenge-paradigms, the study of functional interactions of different neurotransmitter systems is possible. This review will present data from animal and healthy volunteer studies as well as first data from investigations in different patient populations with regard to this research direction. Especially, interactions of different neurotransmitter systems with the dopaminergic and the cholinergic system will be discussed. The database acquired so far confirms existing models of neuronal feedback -circuits, and the first clinical results are consistent with the hypothesis of an increased dopaminergic responsivity in schizophrenic patients. These results open up new perspectives for a further evaluation of treatment response predictors from drug -challenge studies and for the development of new drug treatments for neuropsychiatric disorders.
    Notes: Zusammenfassung Positronenemissionstomographie (PET) und Single Photonenemissionscomputertomographie (SPECT) ermöglichen als funktionelle bildgebende Verfahren die In-vivo-Untersuchung von spezifischen neurochemischen Prozessen im Zusammenhang mit physiologischen Regulationsvorgängen und pathophysiologischen Veränderungen des Gehirns. Durch die Kombination mit pharmakologischen Challenge-Paradigmen kann auf dieser methodischen Grundlage auch den funktionellen Interaktionen zwischen Neurotransmittersystemen nachgegangen werden. In dem vorliegenden Übersichtsartikel werden unter dieser Fragestellung durchgeführte tierexperimentelle Studien, Untersuchungen bei gesunden Probanden sowie klinische Ergebnisse dargestellt. Insbesondere der vielfältige Einfluss auf das dopaminerge und das cholinerge System wird dabei näher betrachtet. Die gewonnenen Daten bestätigen existierende Modelle von neuronalen Feedback-Regelkreisen. Erste klinische Resultate sind konsistent mit Hypothesen einer verstärkten dopaminergen Response bei schizophrenen Patienten. Die bisherigen Ergebnisse eröffnen eine Perspektive für die Entwicklung neuer Strategien zur Therapie neuropsychiatrischer Erkrankungen und bereiten zugleich den Boden für weitere Untersuchungen zur prädiktiven Bedeutung einer Challenge-Antwort bezüglich eines nachfolgenden Therapieerfolgs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001150050002
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  • 11
    Electronic Resource
    Electronic Resource
    Nutrient-dependent distribution of insulin and glucokinase immunoreactivities in rat pancreatic beta cells (1999)
    Springer
    Virchows Archiv 434 (1999), S. 75-82 
    Details
    ISSN: 1432-2307
    Keywords: Key words Rat ; Pancreatic beta cell ; Insulin ; GLUT2 glucose transporter ; Glucokinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Functional heterogeneity among pancreatic beta cells is a characteristic feature of the islets of Langerhans. Under physiological conditions, beta cells in the pancreas of fed rats exhibited heterogeneous immunohistochemical staining for insulin and glucokinase. Intracellular beta cell glucokinase staining was either faint or dense. In the pericapillary space beta cell glucokinase immunoreactivity had a polar orientation, with the highest density in cytoplasmic regions close to the blood vessels. Starvation resulted in a loss of heterogeneity with homogeneous insulin staining in all beta cells of the islets, and this was accompanied by a loss of heterogeneous glucokinase staining. The intracellular polarity of glucokinase staining in contact to blood vessels also disappeared after starvation. Refeeding resulted in the reappearance of intercellular heterogeneity. In dependence on the functional demand, the endocrine pancreas recruited insulin from beta cells according to a well-defined hierarchy, with an initial preferential mobilization of medullary beta cells. In the course of this process intracellular polarity of glucokinase staining reappeared in areas of the beta cell with functional contact to the GLUT2 glucose transporter in the plasma membrane. This can be regarded as the morphological correlate of an activation of the glucose signal recognition apparatus. Interestingly, the study also provides evidence that the changes in glucokinase distribution apparently preceded those in insulin distribution, which is in keeping with the central role of glucokinase as the glucose sensor of the pancreatic beta cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004280050308
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  • 12
    Electronic Resource
    Electronic Resource
    Effects of combination of insulin and acarbose compared with insulin and gliclazide in type 2 diabetic patients (1999)
    Springer
    Acta diabetologica 36 (1999), S. 93-97 
    Details
    ISSN: 1432-5233
    Keywords: Key words Type 2 diabetes mellitus ; Insulin ; Acarbose ; Gliclazide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In this prospective study we aimed to compare insulin plus acarbose with insulin plus gliclazide with respect to their effect on insulin requirement, lipid profiles and body mass index (BMI) while achieving good glycemic control. Forty patients with type 2 diabetes mellitus who were on conventional insulin therapy (subcutaneous insulin therapy consisting of regular and NPH insulin, two times a day) were included in the study. They were randomized to double blind treatment with insulin in combination with gliclazide or acarbose for 6 months. For both groups, acceptable glycemic control was achieved at the end of study period. The mean HbA1c levels decreased from 8.32±0.26 to 7.13±0.18% in acarbose group and 8.6±0.15 to 7.48±0.21% in the gliclazide group. The difference between groups was not significant (P 0.29). In the acarbose group, total cholesterol and LDL concentration decreased significantly while other parameters did not change. In the gliclazide group, HDL levels decreased significantly from 46.6±2.48 mg/dl to 41.3±2.09 mg/dl (P 0.001) BMI increased significantly from 27.60±1.21 kg/m2 to 28.69±1.26 kg/m2. (P 0.003) Total daily insulin dose was not changed in the acarbose group significantly, but increased from 42.6±2.73 to 49.27±3.58 U/day, which was significant in gliclazide group of (P 0.016). In the acarbose group, there were no significant differences between responders and nonresponders with respect to fasting and stimulated C-peptide, HbA1c levels and baseline BMI values. But in the gliclazide group, baseline BMI values were significantly higher in the nonresponding group compared to responders (P 0.02). In conclusion, combination of insulin with acarbose can be a good alternative for type 2 diabetic patients on insulin therapy; seems more beneficial than combination with gliclazide; may have advantage of achieving good glycemic control without increasing insulin dose and BMI; also may have the advantage of providing a decrease in LDL level, which are all important to prevent atherosclerosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005920050151
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  • 13
    Electronic Resource
    Electronic Resource
    Increased glucagon-stimulated insulin secretion of cryopreserved rat islets transplanted into nude mice (1999)
    Springer
    Journal of molecular medicine 77 (1999), S. 107-110 
    Details
    ISSN: 1432-1440
    Keywords: Key words Pancreatic islet transplantation ; Cryopreservation ; Conservation ; Insulin ; Nude mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cryopreservation is the only available technique for long-term storage of pancreatic islets. The freezing/thawing protocol may cause considerable loss of viable islet tissue and impair its function in vivo. The aim of this study was to investigate glucose and insulin levels after transplantation of fresh and cryo/thawed rat islets. Rat pancreatic islets were isolated following intraductal collagenase injection and Ficoll gradient purification. After isolation, islets were cultured for 24 h and then either transplanted or frozen after stepwise addition of DMSO according to Rajotte et al. and stored in liquid nitrogen. After rapid thawing islets were stepwise transferred into RPMI medium and cultured for another 24 h. The recipients were athymic mice with streptozotocine-induced diabetes. Two hundred fresh (n=13) or cryo/thawed (n=15) islets were transplanted beneath the renal capsule. Glucose levels were measured for 14 days and blood samples for insulin determination were obtained 15 min after i.p. glucagon (10 mg/kg) administration on day 14. Glucose levels were normalized (〈9 mmol/l) in all recipients within 3 days since transplantation. On day 14, mean fasting values±SE in fresh and cryo/thawed islet groups were 4.0±0.6 and 4.4±0.4 mmol/l, respectively (P〉0.05). Fasting insulin levels were higher in the cryo/thaw than in the fresh islet group (1.67±0.33 vs 0.57±0.13 ng/ml; P〈0.01). Post-glucagon levels did not differ significantly (1.45±0.24 vs 0.86±0.24 ng/ml; P=0.06). While glucagon significantly increased insulin levels (P〈0.01) in the fresh islet group, no change in insulin levels was observed (P〉0.05) in the cryo/thaw group. Immunohistochemical staining demonstrated fragmentation of viable islet tissue which was more apparent in the cryo/thaw group. We conclude that in a short-term study cryo/thawed rat islets produce higher insulin levels than fresh islets transplanted into nude mice. This may be due to better islet survival or loss of feed-back regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001090050313
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  • 14
    Electronic Resource
    Electronic Resource
    Nachbarschaft von Tic und Zwang (1999)
    Springer
    Der Nervenarzt 70 (1999), S. 1-10 
    Details
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Tic-Störung ; Zwangsstörung ; Kinder ; Jugendliche ; Neurobiologie ; Psycho- pharmakologie ; Verhaltenstherapie ; Key words Tic-disorder ; Obsessive-compulsive disorder ; Children ; Adolescents ; Neurobiology ; Psychopharmacology ; Behavior therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In children and adolescents motor/vocal tics and obsessive-compulsive behavior are known to be closely related. Thereby, a continuum of symptoms ranging from single tics to a mixed picture of tics/rituals/obsessive-compulsive traits to clinically relevant obsessions and compulsions could be described. As neurobiological substrates dysfunctions in corresponding cortico-striato-thalamo-cortical circuits (sensorimotor circuit in tic symptomatology, orbitofrontal circuit in obsessive-compulsive behavior) were postulated. For both disturbances behavioral therapy can be used to improve control mechanisms to counterregulate tics and obsessive-compulsive behavior, respectively, and psychopharmacological agents can be administerd to compensate dysbalances in neurotransmitter systems. In case of a mixed symptomatologic picture it is necessary to include interventions for both pols of the symptom-continuum in the therapeutic programme to achieve extensive improvement as a basis for a further positive development of the patient.
    Notes: Zusammenfassung Motorische/vokale Tics und zwanghafte Verhaltensweisen kommen bei Kindern und Jugendlichen häufig gemeinsam vor; dabei kann ein Symptomkontinuum von solitär auftretenden Tics über ein Mischbild von Tics und Ritualen/zwanghaften Gedanken und/oder Handlungen bis hin zu eindeutigen Zwangsphänomenen beschrieben werden. Neurobiologisch können diesem Symptomkontinuum unterschiedlich ausgebreitete Dysfunktionen entsprechender kortiko-striato-pallido-thalamo-kortikaler Regulationssysteme zugrunde liegen. Therapeutisch lassen sich bei beiden Verhaltensauffälligkeiten mittels verhaltenstherapeutischer Techniken Steuerungs- und Kontrollmöglichkeiten zur Gegenregulation der Auffälligkeiten verbessern sowie durch Einsatz von Psychopharmaka Dysbalancen von Neurotransmittersystemen ausgleichen. Bei einem Mischbild von Tics und Zwängen sind therapeutische Interventionen für beide Zielbereiche erforderlich. Nur so können umfassende Verbesserungen erreicht und günstige Entwicklungsbedingungen für die betroffenen Kinder und Jugendlichen eröffnet werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001150050394
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  • 15
    Electronic Resource
    Electronic Resource
    Gene transfer into insect brain and cell-specific expression of bombyxin gene (1999)
    Springer
    Development genes and evolution 209 (1999), S. 447-450 
    Details
    ISSN: 1432-041X
    Keywords: Key words Bombyxin ; Insulin ; Bombyx mori ; Electroporation ; Cell-specific expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A transgene reporter consisting of the bombyxin gene promoter and the green fluorescent protein coding region was introduced into intact brains of the silkworm Bombyx mori by in vitro electroporation. After in vitro culture of the brains, the fluorescence derived from the introduced reporter gene was observed in all cases in eight neurosecretory cells that had previously been identified as bombyxin-producing cells (BPCs). Although the fluorescence was not always observed in all cells, it was specific to BPCs, indicating that the reporter was under the control of the bombyxin gene promoter in a BPC-specific manner. Electroporatical introduction of a reporter gene was therefore found to be a suitable method for analyzing cell-specific expression in intact tissues and to be substitute for germ-line transmission of reporters in the transgenic system. Application of this technique enables us to analyze the cell-specific expression of transgene reporters within a few days and treat more than several dozens of the reporters within 1 month, which is difficult to do with the transgenic system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050277
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  • 16
    Electronic Resource
    Electronic Resource
    Beyond discounting: possible experimental models of impulse control (1999)
    Springer
    Psychopharmacology 146 (1999), S. 339-347 
    Details
    ISSN: 1432-2072
    Keywords: Key words Hyperbolic discounting ; Impulsivity ; Self-control ; Reward bundling ; Psychopharmacology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Animal studies of impulsivity have typically used one of three models: a delay of reward procedure, a differential reinforcement for low rate responding (DRL) procedure, or an autoshaping procedure. In each of these paradigms, we argue, measurement of impulsivity is implicitly or explicitly equated with the effect delay has on the value of reward. The steepness by which delay diminishes value (the temporal discount function) is treated as an index of impulsivity. In order to provide a better analog of human impulsivity, this model needs to be expanded to include the converse of impulsivity – self-control. Through mechanisms such as committing to long range interests before the onset of temptation, or through bundling individual choices into classes of choices that are made at once, human decision-making can often look far less myopic than single trial experiments predict. For people, impulsive behavior may be more often the result of the breakdown of self-control mechanisms than of steep discount functions. Existing animal models of self-control are discussed, and future directions are suggested for psychopharmacological research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005480
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  • 17
    Electronic Resource
    Electronic Resource
    Insulin modulation of ATP-sensitive K+ channel of rat skeletal muscle is impaired in the hypokalaemic state (1999)
    Springer
    Pflügers Archiv 437 (1999), S. 235-240 
    Details
    ISSN: 1432-2013
    Keywords: Key words Hypokalaemic periodic paralysis ; ATP-sensitive K+ channels ; Insulin ; Skeletal muscle ; Patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In the present work, we examined the effects of in vivo administration of insulin to rats made hypokalaemic by feeding a K+-free diet. The i.p. injection of insulin in the hypokalaemic rats provoked muscle paralysis within 3–5 h. Consistent with this observation, the skeletal muscle fibres of the paralysed rats were depolarized. In contrast, in the normokalaemic animals, insulin neither provoked paralysis nor produced significant fibre hyperpolarization. In the hypokalaemic rats, insulin almost completely abolished the sarcolemma adenosine triphosphate (ATP)-sensitive K+ currents without altering the sensitivity of the channels to ATP or glibenclamide. In contrast, in the normokalaemic rats, insulin enhanced ATP-sensitive K+ currents that became also resistant to ATP and glibenclamide. Our experiments indicate that the modulation of the sarcolemma ATP-sensitive K+ channels by insulin is impaired in the hypokalaemic state. This phenomenon appears to be related to the fibre depolarization and paralysis observed in the same animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050774
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  • 18
    Electronic Resource
    Electronic Resource
    Interleukin-1β-induced nitric oxide synthesis in aortic rings from normal and hyperinsulinaemic rats: effect of physical exercise (1999)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 360 (1999), S. 63-68 
    Details
    ISSN: 1432-1912
    Keywords: Key words Arterial smooth muscle ; Glucose ; Inducible NO synthesis ; Insulin ; Lean and obese Zucker rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Insulin has been suggested to prevent the induction of nitric oxide synthase (NOS) in vitro in arterial smooth muscle, but whether such a mechanism is operative in vivo is not known. Therefore, we evaluated the sensitivity of smooth muscle NOS to induction by interleukin-1β (IL-1β) in aortic rings of lean and obese Zucker rats, a model of experimental hyperinsulinaemia. In order to modulate the insulin and glucose balance of the rats, a 22-week-long treadmill exercise was included in the study. The training attenuated weight gain and reduced blood glucose in the obese and lean rats, whereas the abnormally high plasma insulin of the obese rats remained unaffected. A 6-h incubation of aortic rings with IL-1β (10 ng/ml) increased cyclic GMP in smooth muscle by approximately threefold in all groups, and this effect was prevented by methylene blue. The contractile sensitivity of endothelium-denuded aortic rings to phenylephrine was reduced by incubation with IL-1β (1 ng/ml and 10 ng/ml) in the exercised obese and lean rats, whereas no significant change was observed in the sedentary groups. The aortic maximal contractile force induced by phenylephrine was reduced in sedentary and exercised obese rats by incubation with IL-1β, while no change was detected in the lean rats. The aortic relaxation to exogenous L-arginine was augmented by IL-1β in all groups, while the relaxation sensitivity to L-arginine after induction by IL-1β was enhanced by exercise in the obese but not in the lean rats. Finally, the relaxation to nitroprusside was not significantly affected by IL-1β in any of the study groups. In conclusion, since maximal contractile force generation to phenylephrine was reduced by IL-1β in the obese but not in the lean rats, the sensitivity of NOS to induction by IL-1β was higher in arterial smooth muscle of the obese than the lean Zucker rats. Thus, this model of hyperinsulinaemia was not associated with reduced sensitivity of smooth muscle NOS to induction by IL-1β. Regular exercise did not change plasma insulin concentrations, but it enhanced the action of insulin in both strains as reflected by reduced blood glucose, and increased the sensitivity of smooth muscle NOS to induction by IL-1β.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002109900036
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  • 19
    Electronic Resource
    Electronic Resource
    Forskolin increases apical sodium conductance in cultured toad kidney cells (A6) by stimulating membrane insertion (1999)
    Springer
    Pflügers Archiv 438 (1999), S. 195-204 
    Details
    ISSN: 1432-2013
    Keywords: Key words A6 cells ; Capacitance ; Hormones ; Insulin ; Membrane area ; Membrane traffic ; Renal epithelia ; Water permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The role of membrane traffic in the stimulation of apical Na+ permeability caused by increases in cytoplasmic cyclic AMP was assessed by measuring the effects of forskolin on transepithelial capacitance (C T), transepithelial conductance (G T), and short-circuit current (I sc) in A6 cultured toad kidney cells. Apical water permeability was probed by recording cell volume changes after reducing the osmolality of the apical bath. We found that forskolin does not increase the osmotic water permeability of the apical membrane of A6 cells, and thus does not stimulate the insertion of water channels. Comparison of the effects of forskolin and insulin on Na+ transport demonstrated that both agents produce reversible increases in C T, G T and I sc. G T and C T increased proportionally during the rising phase of the insulin response. However, a non-linear relationship between both parameters was recorded when forskolin was given in NaCl Ringer’s solution. The relationship between C T and G T became linear after the effects of forskolin on Cl– conductances were eliminated by substituting Cl– by an impermeant anion. In contrast, in Cl–-containing Na+-free solutions, the non-linearity became more pronounced. Successive additions of insulin and forskolin caused additive increases in C T. Because increases in C T and Na+ transport occurred in the absence of stimulation of water permeability and increases of C T and G T were directly proportional when Na+ was the major permeating ion across the apical membrane, we suggest that the increase in apical Na+ permeability in the presence of either forskolin or insulin is due to the insertion of channels residing in intracellular pools. In contrast, the increased Cl– permeability caused by forskolin may be related to the activation of channels already present in the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050898
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  • 20
    Electronic Resource
    Electronic Resource
    Metabolic and ultrastructural effects of cyclosporin A on pancreatic islets (1999)
    Springer
    Transplant international 12 (1999), S. 208-212 
    Details
    ISSN: 1432-2277
    Keywords: Key words Cyclosporin A ; Langerhans ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated the effect of different doses of cyclosporin A (CyA) on glucose and insulin levels, as well as its residual effects on pancreatic islets ultrastructure after discontinuation of the drug. We studied four groups of Wistar rats. One control- (n = 5) and three experimental groups, n = 10 each, were treated with different doses of CyA IM for 14 days: group I, 5 mg/Kg; group II, 15 mg/Kg; and group III, 25 mg/Kg. Five animals of each group were sacrificed after 14 days, and the remaining five after 21 days to assess residual CyA effects. On the day of sacrifice, the rats underwent maltose absorption test, and glucose and insulin levels were measured. Pancreatic biopsies were obtained on day 21 to evaluate islets ultrastructure by electron microscopy. As a result, statistically significant, dose dependent (P 〈 0.05) increases in glucose and insulin levels were observed in CyA-treated groups. Groups II and III showed insulin levels significantly higher after fasting (P 〈 0.05) on day 14 comparing to the controls, while in groups I and II values returned to normal after CyA discontinuation. Group III showed persistently increased insulin levels on day 21. Pancreatic ultrastructural changes were observed only in group III. We can conclude that CyA effects on glucose and insulin levels were temporary and reversible at low doses. Ultrastuctural changes in the pancreatic islets may occur with high doses of CyA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001470050212
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  • 21
    Electronic Resource
    Electronic Resource
    Insulin-induzierte Hypoglycaemia factitia aus diätetischen Gründen (1999)
    Springer
    Rechtsmedizin 9 (1999), S. 190-192 
    Details
    ISSN: 1434-5196
    Keywords: Key words Hypoglycaemia factitia ; Insulin ; Diet ; Lethal outcome ; Schlüsselwörter Hypoglykaemia factitia ; Insulin ; Diät ; Tödlicher Verlauf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Wir berichten über den Fall einer 28jährigen, nicht insulinpflichtigen nicht-Diabetikerin, in deren Anamnese eine hypoglykaemische Episode vor dem Todeseintritt bekannt wurde. Autoptisch wurde eine (heimliche) Applikation von Insulin durch letal hohe Insulinspiegel im zentralen und peripheren Blut mit Hypoglykaemie diagnostiziert. Nach der Anamnese, den Ergebnissen des Ermittlungsverfahrens und der Autopsie konnte die Applikation von Insulin aus suizidaler und homizidaler Absicht oder im Rahmen eines Münchhausen-Syndroms ausgeschlossen werden. Vielmehr handelte es sich in der Gesamtschau um eine Hypoglykaemia factitia aus diätetischen Gründen.
    Notes: Abstract The medical history of a 28-year-old non-insulin-dependent and non-diabetic patient with a hypoglycaemic episode before death is reported. At autopsy, an (surreptious) insulin administration was documented by lethally high serum insulin in central and peripheral blood during hypoglycaemia, According to the anamnesis, the judical inquiry and the autopsy findings, a suicidal intent, murder by insulin or Munchhausen-syndrome could be excluded. We therefore diagnosed a hypoglycaemia factitia caused by the diet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001940050107
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  • 22
    Electronic Resource
    Electronic Resource
    Effect of moderate physical activity on plasma leptin concentration in humans (1999)
    Springer
    European journal of applied physiology 79 (1999), S. 331-335 
    Details
    ISSN: 1439-6327
    Keywords: Key words Leptin ; Exercise Energy balance ; Insulin ; Glucocorticoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In subjects who maintain a constant body mass, the increased energy expenditure induced by exercise must be compensated by a similar increase in energy intake. Since leptin has been shown to decrease food intake in animals, it can be expected that physical exercise would increase energy intake by lowering plasma leptin concentrations. This effect may be secondary either to exercise-induced negative energy balance or to other effects of exercise. To delineate the effects of moderate physical activity on plasma leptin concentrations, 11 healthy lean subjects (4 men, 7 women) were studied on three occasions over 3 days; in study 1 they consumed an isoenergetic diet (1.3 times resting energy expenditure) over 3 days with no physical activity; in study 2 the subjects received the same diet as in study 1, but they exercised twice daily during the 3 days (cycling at 60 W for 30 min); in study 3 the subjects exercised twice daily during the 3 days, and their energy intake was increased by 18% to cover the extra energy expenditure induced by the physical activity. Fasting plasma leptin concentration (measured on the morning of day 4) was unaltered by exercise [8.64 (SEM 2.22) 7.17 (SEM 1.66), 7.33 (SEM 1.72) 1μg · l−1 in studies 1, 2 and 3, respectively]. It was concluded that a moderate physical activity performed over a 3-day period does not alter plasma leptin concentrations, even when energy balance is slightly negative. This argues against a direct effect of physical exercise on plasma leptin concentrations, when body composition is unaltered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050516
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  • 23
    Electronic Resource
    Electronic Resource
    Genome-wide scanning for type 2 diabetes susceptibility in Canadian Oji-Cree, using 190 microsatellite markers (1999)
    Springer
    Journal of human genetics 44 (1999), S. 10-14 
    Details
    ISSN: 1435-232X
    Keywords: Key words Complex disease ; Carbohydrate ; Insulin ; Aboriginal populations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We undertook a genome-wide scan using 190 markers with an average separation of 20 cM in 49 Canadian Oji-Cree sib pairs affected with type 2 diabetes. Four of these markers, one each on chromosomes 6, 8, 16, and 22, showed both suggestive linkage and suggestive association with type 2 diabetes in the Oji-Cree. None of these markers corresponded to any chromosomal region or marker that has so far been linked with type 2 diabetes in other populations. Thus, there might be several genetic loci that confer susceptibility to type 2 diabetes in this study sample. We are following up on these preliminary leads by increasing the density of the markers within these linked and associated regions, and also by increasing the number of study subjects. Also, we found instances in which there were wide disparities between the Oji-Cree and reference Caucasians with respect to marker heterozygosity. This suggests that a particular set of markers for genome-wide scanning will have different informativeness in different ethnic groups. Thus, different marker sets will likely be required for different ethnic groups in order to maximize their information content for linkage calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100380050097
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  • 24
    Electronic Resource
    Electronic Resource
    The effect of euglucaemic hyperinsulinaemia on forearm blood flow and glucose uptake in the human forearm (1998)
    Springer
    Acta diabetologica 35 (1998), S. 203-206 
    Details
    ISSN: 1432-5233
    Keywords: Key words Glucose ; Insulin ; Hyperinsulinaemia ; Blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Insulin-mediated stimulation of blood flow to skeletal muscle has been proposed to be of major importance for insulin-mediated glucose uptake. The aim of this study was to investigate the relative importance of blood flow and glucose extraction as determinants of insulin-mediated glucose uptake in the human forearm. Forearm blood flow (FBF), glucose extraction and oxygen consumption were evaluated for 100 min during the euglycaemic hyperinsulinaemic clamp (92 mU/l) in nine healthy subjects. FBF was measured by venous occlusion plethysmography. Forearm glucose uptake increased sevenfold during the hyperinsulinaemia (P〈0.001). Forearm glucose extraction showed a minor increase during the first 10 min of hyperinsulinaemia, but the most marked increase took place between 10 and 20 min (+170%). Thereafter, only a minor further increase was seen. During the first 10 min of hyperinsulinaemia FBF was unchanged. Thereafter, FBF increased steadily to a plateau reached after 60 min (+50%, P〈0.001). A close relationship between whole body glucose uptake and FBF was seen at the end of the clamp (r = 0.75, P〈0.02), but at this time the relationship between whole body glucose uptake and forearm glucose extraction was not significant. The modest increase in O2 consumption seen at the beginning of the clamp (+19%) was not related to FBF during the early phase of the clamp. In conclusion, the early course of insulin-mediated glucose uptake in the human forearm was mainly due to an increase in glucose extraction. However, with time the insulin-mediated increase in blood flow increased in importance and after 100 min of hyperinsulinaemia FBF was the major determinant of glucose uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005920050132
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  • 25
    Electronic Resource
    Electronic Resource
    Functioning human insulinomas (1998)
    Springer
    Virchows Archiv 433 (1998), S. 495-504 
    Details
    ISSN: 1432-2307
    Keywords: Key words Insulinomas ; Prohormone convertases ; Carboxypeptidase H ; Insulin ; Proinsulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Sixty-seven insulinomas were investigated by immunohistochemistry using site-directed antibodies against insulin, proinsulin, chromogranin A, HISL-19, and four proteins directly or indirectly involved in the proteolytic processing of proinsulin: the prohormone convertases PC2 and PC3, carboxypeptidase H (CPH) and 7B2. Results were expressed in a six-grade score according to the frequency of immunoreactive tumour cells. Insulin was expressed by all tumours, appearing in either a diffuse or a polarized pattern and being detected in more than 30% of tumour cells in all cases but three. Proinsulin was also expressed in all tumours, with more than 50% of tumour cells immunoreactive in all cases but 5. It was consistently localized in the Golgi apparatus. In about half the cases, moreover, it also showed diffuse cytoplasmic staining, usually with a very sparse distribution. Trabecular and solid insulinomas did not present specific, homogeneous patterns of insulin immunostaining. However, insulin immunoreactivity was much more abundant in trabecular than in solid neoplasms, being present in virtually all tumour cells (score 6) in 50% and 8% of cases, respectively. Virtually all insulinomas expressed PC2, PC3, CPH and 7B2, usually in 30–100% of tumour cells, with a frequency significantly related to that of insulin. However, detection of PC2 and 7B2 was slightly less frequent than that of PC3 and CPH. In consecutive sections these proteins were found to be mostly co-localized with insulin and chromogranin A but not with proinsulin. They were heavily expressed in all 10 tumours with more than 10% of cells showing cytoplasmic proinsulin immunoreactivity, indicating that the leakage of proinsulin from the Golgi compartment is not associated with faulty expression of converting enzymes and possibly reflects a saturated processing capacity. HISL-19 immunoreactivity was found in both Golgi apparatus and insulin stores, indicating that the relevant antigen is different from all other proteins investigated. These results do not support a defect in expression or localization of proinsulin-processing enzymes in most insulinomas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004280050280
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  • 26
    Electronic Resource
    Electronic Resource
    Neuropathy in diabetic BB/Wor rats treated with insulin implants (1998)
    Springer
    Acta neuropathologica 96 (1998), S. 144-150 
    Details
    ISSN: 1432-0533
    Keywords: Key words Neuropathy ; Hypoglycaemia ; Hyperglycaemia ; Insulin ; BB/Wor rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To elucidate the pathophysiology of diabetic neuropathy many workers have examined nerve specimens from diabetic rats. While most workers found that animals with high blood glucose levels develop neuropathy, some researchers report that the peripheral nerves are normal in hyperglycaemic rats. Hypoglycaemia may also cause neuropathy. Some workers suggest that neuropathy is linked to fluctuations of the blood glucose level. In the present study we examine plantar nerves of diabetic BB/ Wor rats maintained on an eu-/hyperglycaemic or an eu-/ hypoglycaemic regime with insulin implants. Treatment with implants worked well. Light microscopic examination of nerve fibres in non-diabetic control rats and in eu-/ hyperglycaemic diabetic rats showed a normal picture. Preparations from eu-/hypoglycemic rats showed irregular myelin sheaths and signs of Wallerian degeneration. The lengths and diameters of the largest internodes were significantly subnormal. We conclude, that periodic moderate hypoglycaemia, but not periodic moderate hyperglycaemia, elicits neuropathy in diabetic BB/Wor rats treated with insulin implants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050874
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  • 27
    Electronic Resource
    Electronic Resource
    Hypoglycaemic neuropathy in BB/Wor rats treated with insulin implants: electron microscopic observations (1998)
    Springer
    Acta neuropathologica 96 (1998), S. 151-156 
    Details
    ISSN: 1432-0533
    Keywords: Key words Neuropathy ; Hypoglycemia ; Insulin ; implant ; Rat ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Insulin-dependent diabetes mellitus is a chronic metabolic disease that causes long-term secondary complications such as neuropathy. The occurrence of diabetic neuropathy has generally been thought of as being associated with hyperglycaemia. However, in a previous light microscopic examination of plantar nerves in diabetic BB/Wor rats treated with insulin implants we found that eu-/hyperglycaemic rats present a normal picture, whereas eu-/hypoglycaemic rats show severe changes. The aim of the present work is to supplement our previous light microscopic report with electron microsocpic data from the lateral plantar nerve of normal, eu-/hyperglycaemic and eu-/hypoglycaemic BB/Wor rats. Under the electron microscope lateral plantar nerves collected from eu-/hyperglycaemic rats presented a qualitatively normal picture. In addition, the fibre numbers and the size distribution of the myelinated fibres were normal. In contrast, specimens from eu-/hypoglycaemic BB/Wor rats showed severe qualitative changes, interpreted as signs of axonal de- and regeneration. The total number of axons was somewhat subnormal and the sizes of the myelinated fibres were strongly shifted towards smaller diameters. These data confirm our previous light microscopic observations. We conclude that eu-/hypoglycaemic BB/Wor rats treated with insulin implants, but not similarly treated eu-/hyperglycaemic animals, develop a neuropathy in their plantar nerves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050875
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  • 28
    Electronic Resource
    Electronic Resource
    A novel member of the bombyxin gene family: structure and expression of bombyxin G1 gene, an insulin-related peptide gene of the silkmoth Bombyx mori (1998)
    Springer
    Development genes and evolution 208 (1998), S. 407-410 
    Details
    ISSN: 1432-041X
    Keywords: Key words Bombyxin ; Insulin ; Bombyx mori ; Multigene family ; Brain neurosecretory cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Bombyxin G1 gene, a novel insulin-related peptide gene of the silkmoth Bombyx mori, has been identified. The G1 gene encodes a precursor peptide which shows 41–56% and 28% sequence identities with preprobombyxins previously characterized and human preproinsulin, respectively. The G1 gene forms a pair with bombyxin C2 gene with opposite transcriptional orientation in a bombyxin gene cluster. The bombyxin G1 mRNA in Bombyx brain was shown to locate in four pairs of medial neurosecretory cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050197
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  • 29
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    Electronic Resource
    Cyclosporin A induces apoptosis in rat hepatocytes in culture (1998)
    Springer
    Archives of toxicology 72 (1998), S. 559-565 
    Details
    ISSN: 1432-0738
    Keywords: Key words Proliferation ; Epidermal growth factor (EGF) ; Insulin ; Hepatocyte ; Cyclosporin A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cyclosporin A (CsA) at concentrations up to 1 μM induced apoptosis in a dose-dependent manner in cultured rat hepatocytes for 48 h in the presence of insulin and epidermal growth factor (EGF). The effect of CsA was evidenced by the DNA fragmentation pattern constituted by fragments of multiples of 180–200 base pairs, which is a characteristic of programmed cell death. The metabolic activity did not change significantly in the presence of 0.1 μM CsA and diminished to 49% of control in the presence of 1 μM CsA. Changes in the metabolic activity were correlated with a decrease in both [methyl-3H]thymidine uptake and DNA content, which reflects a decrease in the cell number. The treatment of cells with CsA (1 μM) decreased the metabolic activity/DNA content ratio by 24% with respect to dimethyl sulphoxide (DMSO) control, which also suggests, under these conditions, that the necrosis achieved is at most only 24%. In addition, the changes observed (apoptotic process, arrest of the cell cycle and apparition of a necrotic process) were correlated with an increase in the high-affinity guanosine triphosphatase (GTPase) enzymes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050543
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  • 30
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    Electronic Resource
    Slowly deteriorating insulin secretion and C-peptide production characterizes diabetes mellitus in infantile cystinosis (1998)
    Springer
    European journal of pediatrics 157 (1998), S. 738-742 
    Details
    ISSN: 1432-1076
    Keywords: Key words Diabetes mellitus ; Infantile cystinosis ; Insulin ; C-peptide ; Chronic renal failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Infantile cystinosis, a rare lysosomal storage disease of cystine, leads to Fanconi syndrome and end-stage renal failure. After renal transplantation, no recurrence of the disease occurs in the graft, but other organ involvement becomes evident later in life. Diabetes mellitus has been associated with cystinosis, but the mechanisms of impaired glucose tolerance have not yet been characterized. Here, we studied glucose tolerance, glucose constant decay (k-values), insulin and C-peptide by intravenous glucose tolerance test (IVGTT) in eight patients with infantile cystinosis (three with impaired GFR (CRF) and five after kidney transplantation (KTX)). For comparison, 15 age-matched children with CRF and 15 age-matched KTX patients were analysed. Both early and second insulin secretion phases were diminished in patients with infantile cystinosis, whereas in CRF, k-values were no different from control patients. After renal transplantation, k-values were significantly lower in cystinotic patients with a markedly reduced early insulin secretion phase. There was a significant negative correlation between k-values and age in patients with cystinosis. Repetitive IVGTTs in these patients demonstrated progressive but rather slow loss of first phase insulin secretion and C-peptide production, suggesting a slowly reducing secretion potential of the beta cell due to cystine storage. Conclusion Unlike type I diabetes mellitus, glucose intolerance in patients with infantile cystinosis is characterized by a slow, progressive loss of insulin secretion and C-peptide production. For these patients, the data indicate a 50% risk of developing glucose intolerance by the age of 18 years. We recommend to perform intravenous glucose tolerance tests at 5-year intervals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004310050926
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    Expression of type III hyperlipoproteinemia in patients homozygous for apolipoprotein E-2 is modulated by lipoprotein lipase and postprandial hyperinsulinemia (1998)
    Springer
    Journal of molecular medicine 76 (1998), S. 355-364 
    Details
    ISSN: 1432-1440
    Keywords: Key words Postprandial hyperlipoproteinemia ; Lipoprotein lipase ; Insulin ; Apolipoprotein E ; Hyperlipoproteinemia type III
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Type III hyperlipoproteinemia (HLP) is a multifactorial disorder associated with homozygosity for the apolipoprotein (apo) E-2 allele. Factors which may promote the development of HLP include lipoprotein lipase (LPL) and hyperinsulinemia. These factors were investigated in eight patients with type III HLP and in nine normolipidemic controls. In vitro the interaction of apoE with LPL was analyzed in cell binding assays. All type III HLP patients showed delayed triglyceride (TG) clearance and remnant lipoprotein accumulation in an oral fat tolerance test. Normolipidemic apoE-2/2 controls revealed normal TG clearance comparable to apoE3/3 controls. HLP patients showed lower LPL activity and mass than controls. Analysis of the LPL gene revealed an Asn 291→Ser mutation in three patients and a –93 T-G substitution combined with an Asp 9→Asn mutation in one control subject. In addition to LPL abnormalities, postprandial hyperinsulinemia was observed in five out of eight patients. In vitro LPL compensated the defective function of apoE-2 in mediating remnant lipoprotein binding to cells. In summary, seven out of eight patients with type III HLP showed LPL abnormalities and/or postprandial hyperinsulinemia. Together with the in vitro data these findings support a coordinate effect of apoE and LPL for the manifestation of type III HLP. Hyperinsulinemia appears to be an additional factor important for disease expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001090050227
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    Electronic Resource
    Cellular regulation of islet hormone secretion by the incretin hormone glucagon-like peptide 1 (1998)
    Springer
    Pflügers Archiv 435 (1998), S. 583-594 
    Details
    ISSN: 1432-2013
    Keywords: Key words GLP-1 ; cAMP ; Insulin ; Calcium ; NIDDM ; Glucagon ; Islet ; GIP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Glucagon-like peptide 1 is a gastrointestinally derived hormone with profound effects on nutrient-induced pancreatic hormone release. GLP-1 modulates insulin, glucagon and somatostatin secretion by binding to guanine nucleotide binding protein-coupled receptors resulting in the activation of adenylate cyclase and generation of cyclic adenosine monophosphate (cAMP). In the B-cell, cAMP, via activation of protein kinase A, interacts with a plethora of signal transduction processes including ion channel activity, intracellular Ca2+ handling and exocytosis of the insulin-containing granules. The stimulatory action of GLP-1 on insulin secretion, contrary to that of the currently used hypoglycaemic sulphonylureas, is glucose dependent and requires the presence of normal or elevated concentrations of the sugar. For this reason, GLP-1 attracts much interest as a possible novel principle for the treatment of human type-2 diabetes. Here we review the actions of GLP-1 on islet cell function and attempt to integrate current knowledge into a working model for the control of pancreatic hormone secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050558
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    Synthesis, homopolymerization, and block copolymerization of N-ethyl-2-ethynyl-pyridinium trifluoromethanesulfonate with styrene and butadiene (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 703-712 
    Details
    ISSN: 0887-624X
    Keywords: synthesis ; homopolymerization ; block copolymerization ; N-ethyl-2-ethyl-pyridinium ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel acetylenic monomer 2-N-ethyl pyridinium trifluoromethane sulfonate (2EPyEtTf) was synthesized and polymerized. Diblock copolymers of 2EPyEtTf with styrene and with butadiene were prepared. Initiation of the polymerization by living anionic polystyryl--Li+ and polybutadienyl--Li+ (Scheme 1) resulted in polystyrene-block-poly(N-ethyl-2-ethynylpyridinium trifluoromethanesulfonate) (PS57PA8), and polybutadiene -block-poly(N-ethyl-2-ethynylpyridinium trifluoromethanesulfonate) (PB30PA8). These amphiphilic block molecules contain rigid, conjugated, and strongly hydrophilic polyacetylene chain fragments attached to hydrophobic polystyrene or flexible polybutadiene chain fragments. The structure of these copolymers was studied by FTIR, UV-visible, and NMR spectroscopy. GPC and viscometry were also used to obtain information on the molecular mass and the molecular mass distribution. Thermal behavior was investigated by means of TGA and DSC. Both block copolymers were shown to form stable monolayers at the air-water interface. The positively charged rigid polyacetylene portion of the copolymer is believed to be partially submerged, while the more flexible hydrophobic chains are forced out of the water. Multilayers of PB30PA8 deposited using the Langmuir-Blodgett technique were found to be less uniform than in the case of the previously reported polystyrene-block-poly(2EPyMeTf) (PS12PA4) copolymer (Balogh et al., Macromolecules, 29, 1996). Polycation-polyanion self-assembly deposition was also investigated, using polystyrenesulfonate (PSS) as polyanion. While PS57PA8/PSS layer-by-layer deposition was not uniform, it was found that PB30PA8/PSS gave homogenous and stable films on hydrophilic glass substrates. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 703-712, 1998
    Additional Material: 8 Ill.
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    Electronic Resource
    Kinetics of the photoinitiated inverse microemulsion polymerization of 2-methacryloyl oxyethyl trimethyl ammonium chloride (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 737-748 
    Details
    ISSN: 0887-624X
    Keywords: inverse microemulsion polymerization ; MADQUAT ; nucleation ; photopolymerization ; molecular weights ; flocculants ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of inverse microemulsions of 2-methacryloyl oxyethyl trimethyl ammonium chloride stabilized by a blend of nonionic emulsifiers (a sorbitan sesquioleate and a sorbitan monooleate) and initiated by UV light in the presence of Azobis(isobutyronitrile) (AIBN) was investigated. The effect of initiator concentration, light intensity, emulsifier concentration, and dispersed phase weight fraction on the polymerization rate (Rp), number of polymer particles (Np), and polymer molecular weight (Mw) was studied. The application of this process to tubular reactors is discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 737-748, 1998
    Additional Material: 15 Ill.
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  • 35
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    Electronic Resource
    Molecular weight distribution of crosslinked polymers produced in emulsion (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1127-1156 
    Details
    ISSN: 0887-624X
    Keywords: emulsion polymerization ; crosslinking and long-chain branching ; molecular weight distribution ; compartmentalization ; gel formation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A kinetic model for evaluating the chain length distribution of a branched polymer produced in emulsion was developed. Chain branching occurring through any intermolecular mechanism is considered, namely, crosslinking, chain transfer to polymer and propagation to terminal double bond. The model accounts for active chain compartmentalization and, when coupled to a model able to describe the evolution of the polymerization system, allows evaluation of the cumulative properties of the produced polymer both in the pregel and postgel phases. The numerical difficulties related to the description of a rather wide polymer chain population and of gel formation are overcome by using the ‘numerical fractionation’ technique. A parametric analysis of both instantaneous and cumulative properties is reported and discussed, with special attention to the role of radical compartmentalization in determining the molecular weight properties of a polymer produced in emulsion. Significant differences with the molecular weights computed using models developed for homogeneous (non compartmentalized) systems have been found. A comparison with the predictions of Flory's statistical theory is also reported in terms of gel point and gel weight fraction. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1127-1156, 1998
    Additional Material: 12 Ill.
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  • 36
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    Electronic Resource
    Cationic copolymerization of cyclic ketene acetals: The effect of substituents on reactivity (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 861-871 
    Details
    ISSN: 0887-624X
    Keywords: 2-methylene-1,3-dioxane ; 4-methyl-2-methylene-1,3-dioxane ; 4,4,6-trimethyl-2-methylene-1,3-dioxane ; 2-methylene-1,3-dioxolane ; 4-methyl-2-methylene-1,3-dioxolane ; 4,5-dimethyl-2-methylene-1,3-dioxolane ; cationic copolymerization ; reactivity ratio ; relative reactivity ; ring-retained polymerization ; cyclic ketene acetals ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cationic copolymerizations of 4-methyl-2-methylene-1,3-dioxane, 2 (M1), with 2-methylene-1,3-dioxane, 1 (M2); of 4,4,6-trimethyl-2-methylene-1,3-dioxane, 3 (M1), with 2-methylene-1,3-dioxane, 1 (M2); of 4-methyl-2-methylene-1,3-dioxolane, 5 (M1), with 2-methylene-1,3-dioxolane, 4 (M2); and of 4,5-dimethyl-2-methylene-1,3-dioxolane, 6 (M1), with 2-methylene-1,3-dioxolane, 4 (M2) were conducted. The reactivity ratios for these four types of copolymerizations were r1 = 1.73 and r2 = 0.846; r1 = 2.26 and r2 = 0.310; r1 = 1.28 and r2 = 0.825; r1 = 2.23 and r2 = 0.515, respectively. The relative reactivities of these monomers towards cationic polymerization are: 3 〉 2 〉 1; and 6 〉 5 〉 4. With both five- and six-membered ring cyclic ketene acetals, the reactivity increased with increasing methyl substitution on the ring. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 861-871, 1998
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    Electronic Resource
    Enzymatic activity of trypsin adsorbed on temperature-sensitive composite polymer particles (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 883-888 
    Details
    ISSN: 0887-624X
    Keywords: temperature sensitive ; particle ; emulsion polymerization ; morphology ; adsorption ; enzyme ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two kinds of temperature-sensitive composite polymer particles were prepared by seeded emulsion copolymerizations of (dimethylamino)ethyl methacrylate and ethylene glycol dimethacrylate with 0.14 μm-sized polystyrene and 0.26 μm-sized poly(methylmethacrylate) seed particles. To evaluate the usefulness as a carrier for biomolecules, the enzymatic activities of trypsin adsorbed on these two composite polymer particles were measured at temperatures above and below each lower critical solution temperature (LCST). In both cases, adsorbed trypsin retained its enzymatic activity during repeated adsorption/desorption measurements. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 883-888, 1998
    Additional Material: 7 Ill.
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  • 38
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    Electronic Resource
    Synthesis of (1→6)-2,5-anhydro-D-glucitol through cyclopolymerization of 3,4-di-O-allyl-1,2 : 5,6-dianhydro-D-mannitol and optical resolution ability of its derivative in HPLC (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 901-909 
    Details
    ISSN: 0887-624X
    Keywords: (1→6)-2,5-anhydro-D-glucitol ; HPLC ; optical resolution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cyclopolymerization of 3,4-di-O-allyl-1,2 : 5,6-dianhydro-D-mannitol (1) was carried out using BF3·OEt2 and t-BuOK. The polymer obtained by the polymerization with BF3·OEt2 mainly consisted of (1→6)-bonded 3,4-di-O-allyl-2,5-anhydro-D-glucitol as the five-membered constitutional repeating unit, though it contained a small amount of other cyclic repeating units. On the other hand, during the polymerization using t-BuOK, the stereoregular polymer (1→6)-linked 3,4-di-O-allyl-2,5-anhydro-D-glucitol (2) was synthesized via a regio- and stereoselective mechanism. Cleavage of the allyl ether linkage in polymer 2 occurred to produce the polymer consisting of only 2,5-anhydro-D-glucitol units, i.e., (1→6)-2,5-anhydro-D-glucitol (3). Chromatographic enantioseparation of chloroquine and tröger base has been performed on (3,5-dimethylphenyl)carbamate and 4-methylbenzoate derivatives of 3 as a chiral stationary phase for high-performance liquid chromatography. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 901-909, 1998
    Additional Material: 4 Ill.
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  • 39
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    Electronic Resource
    Model structures of thermoplastic polyesters having regularly alternated aromatic and fluorinated segments (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 939-947 
    Details
    ISSN: 0887-624X
    Keywords: fluorine ; perfluoropolyether ; polyester ; segmented ; thermoplastic ; interfacial synthesis ; thermal transitions ; dynamic-mechanical properties ; chemical resistance ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linear segmented polyesters containing soft perfluoropolyether (PFPE) and hard aromatic segments are obtained by an interfacial polycondensation reaction of an acyl chloride-ended fluorinated prepolymer with various aromatic diphenols in the presence of phase transfer catalysts (PTC) as accelerators. Experimental conditions for reaching high molecular weights are discussed. The calorimetric analysis (DSC) of all the polyesters synthesized shows a typical biphasic morphology, where a very low Tg (〈 -110°C) corresponding to the segregated PFPE moiety, is always accompanied by another Tg or a higher melting temperature, depending on the nature of the hard phase. Dynamic-mechanical analysis (DMA) has been carried out confirming the DSC results and suggesting diversified mechanical behaviors at the various temperatures in line with the amorphous or semicrystalline nature of the polymer. Chemical resistance was finally tested by dipping in several solvents and chemicals. The new polyesters show high contact angles, a moderate swelling in many organic solvents and excellent stability in aggressive hydrolytic environments. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 939-947, 1998
    Additional Material: 6 Ill.
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  • 40
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    Electronic Resource
    Thermosensitive lactitol-based polyether polyol (LPEP) hydrogels (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 979-984 
    Details
    ISSN: 0887-624X
    Keywords: lactitol ; hydrogel ; polyether polyol ; PEO and PPO linkage ; swelling degree ; thermosensitivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of new thermosensitive polymer hydrogels were prepared by reacting acylated poly(ethylene glycol) bis(carboxymethyl) ether (PEGBCOCl) with lactitol-based polyether polyols (LPEP). The polyether polyols were generated from propoxylation of lactitol and have molecular weights ranging from 1337 to 4055 g/mol. The hydrogels absorb water up to 1000% of their dry weight and expel free water at temperatures at and above 30°C. The wide ranging swelling behavior and excellent thermosensitivity depend closely on the degree of crosslinking and the propylene oxide lengths in the polyols. Differential scanning calorimetry of the hydrogels showed two endotherms associated with the phase transitions of PO and EO segments in the hydrogel structures. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 979-984, 1998
    Additional Material: 4 Ill.
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    Kinetic and microstructure studies of poly(ethylene-co-p-methylstyrene) copolymers prepared by metallocene catalysts with constrained ligand geometry (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1017-1029 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper discusses the poly(ethylene-co-p-methylstyrene) copolymers prepared by metallocene catalysts, such as Et(Ind)2ZrCl2 and [C5Me4(SiMe2NtBu)]-TiCl2, with constrained ligand geometry. The copolymerization reaction was examined by comonomer reactivity (reactivity ratio and comonomer conversion versus time), copolymer microstructure (DSC and 13C-NMR analyses) and the comparisons between p-methylstyrene and other styrene-derivatives (styrene, o-methylstyrene and m-methylstyrene). The combined experimental results clearly show that p-methylstyrene performs distinctively better than styrene and its derivatives, due to the cationic coordination mechanism and spatially opened catalytic site in metallocene catalysts with constrained ligand geometry. A broad composition range of random poly(ethylene-co-p-methylstyrene)copolymers were prepared with narrow molecular weight and composition distributions. With the increase of p-methylstyrene concentration, poly(ethylene-co-p-ethylstyrene)copolymer shows systematical decrease of melting point and crystallinity and increase of glass transition temperature. At above 10 mol % of p-methylstyrene, the crystallinity of copolymer almost completely disappears. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1017-1029, 1998
    Additional Material: 8 Ill.
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  • 42
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    Synthesis and spinning of a thermotropic liquid crystal copolyester containing a semirigid cycloaliphatic spacer (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1473-1480 
    Details
    ISSN: 0887-624X
    Keywords: thermotropic polymers ; liquid crystalline polymers ; semirigid spacers ; melt spinning ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A thermotropic, liquid crystalline copolyester, based on 2-chlorohydroquinone, 1,4-cyclohexanedimethanol and terephthaloyl chloride, has been synthesized and melt spun. The cyclohexanedimethylene moiety acts as a semirigid spacer, introducing flexibility while preserving the thermotropic nature of the polymer. Melt-spun fibers were observed to have a high degree of molecular alignment owing to the nematic nature of the melt. Both polymer and fiber properties have been characterized. Characterization techniques used to this end include elemental analysis, hot-stage polarized light microscopy, scanning electron microscopy, dilute solution viscometry, Fourier transform infrared spectroscopy, nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1473-1480, 1998
    Additional Material: 9 Ill.
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    Synthesis and properties of copolymers from 2-hydroxyethyl methacrylate-linked nonsteroidal antiinflammatory agents with methacrylic acid (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1481-1490 
    Details
    ISSN: 0887-624X
    Keywords: ibuprofen ; ketoprofen ; naproxen ; copolymer reactivity ; thermal stability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three nonsteroidal antiinflammatory drugs, 2-(4-isobutylphenyl)-propionic acid (ibuprofen), 2-(3-benzoylphenyl)-propionic acid (ketoprofen), and 2-(6-methoxy-2-naphthyl)-propionic acid (naproxen), were covalently linked with 2-hydroxyethyl methacrylate (HEMA). The drug-linked HEMA (M1) (ibuprofen-linked HEMA abbreviated as HI; ketoprofen-linked HEMA as HK, and naproxen-linked HEMA as HN), were respectively copolymerized with methacrylic acid (M2), MA, to obtain macromolecular prodrugs. The compositions of the copolymers were determined by means of a 1H-NMR spectroscopy and monomer reactivity ratios were estimated using the Kelen-Tüdös linear differential equation. The reactivity ratios are: r1 = 0.101 ± 0.012, r2 = 1.071 ± 0.065 for HI-MA; r1 = 0.344 ± 0.066, r2 = 0.966 ± 0.032 for HN-MA, and r1 = 0.650 ± 0.182, r2 = 1.032 ± 0.106 for HK-MA, respectively. The monomer reactivity toward to MA radical estimated from 1/r2 values is almost same for all three monomers (1/r2 ∼ 1). The glass transition temperatures of three drug-linked homopolymers go hand in hand with the steric hindrance of three drugs, i.e., ketoprofen 〉 naproxen ≫ ibuprofen calculated the minimum energy by computer molecular modeling. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1481-1490, 1998
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  • 44
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    Liquid chromatography of macromolecules at the critical adsorption point. II. Role of column packing: Bare silica gel (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1363-1371 
    Details
    ISSN: 0887-624X
    Keywords: liquid chromatography ; column packing ; bare silica gel ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Liquid chromatography of macromolecules at the critical adsorption point (LC CAP) presents a potentially very powerful method for molecular characterization of complex polymers. However, LC CAP applicability is limited due to various experimental problems. The pore sizes and surface chemistry of the column packings belong to the most important weak points of the method. The LC CAP behavior of poly(methyl methacrylate)s was investigated using bare silica gels of 6, 12, and 100 nm pore sizes and with various amounts of surface silanols. Tetrahydrofuran as the adsorption suppressing liquid and toluene as the adsorption promoting liquid were mixed to form the “nearly critical” eluents. Both pore size and surface chemistry of silica were found to strongly influence the retentive characteristics of the system in the critical adsorption area. Macromolecules that were large enough to be excluded from the packing pores hardly followed the LC CAP rules: their retention volumes changed irregularly with the polymer molar mass and their recovery dropped sharply. The narrow pore silica gel-packed column governed the elution patterns of the whole column set composed of silica gels with different pore sizes. This makes the conventional LC CAP characterization of common polymers with broader molar mass distribution impractical and even not feasible. A hybrid column system was proposed containing narrow pore nonadsorptive column added in series to the meso- and macroporous LC CAP silica gels. This narrow pore column would allow separation of gas, impurities, and system peaks from the polymer peaks. The possible successive changes of the surface of silica gel, e.g., due to formation of silanols by hydrolysis or due to irreversible adsorption of some admixtures from the sample or eluent may make the LC CAP irrepeatable. Pronounced peak broadening was observed in the critical adsorption area and this effect increased strongly with the polymer molar mass. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1363-1371, 1998
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    New polymer syntheses. XCVII. Hyperbranched LC-polyesters based on β-(4-hydroxyphenyl)propionic acid and 4-hydroxybenzoic acid (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1397-1405 
    Details
    ISSN: 0887-624X
    Keywords: hyperbranched polyesters ; nematic phase ; phloritic acid ; vectra ; melt rheology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two classes of liquid crystalline hyperbranched copolyesters were prepared by the copolycondensation of silylated 3,5-bis(acetoxy)benzoic acid with mixtures of mesogenic difunctional monomers. The first class of LC-copolyesters was obtained from 1 : 1 mixtures (molar ratio) of silylated β-(4-acetoxyphenyl)propionic acid and silylated 4-acetoxybenzoic acid (poly(HPPA/HBA)). The second class of LC-copolyesters was obtained by additional copolycondensation of silylated 6-acetoxy-2-naphthoic acid. The hyperbranched copolyesters of this ternary system poly(HPPA/HBA/HNA) proved to be less crystalline in contrast to the binary system. In both classes of LC-copolyesters the degree of branching was varied via the feed ratio of 3,5-dihydroxybenzoic acid. A minimum segment length of 6 difunctional monomer units between the branching points is required to establish a nematic phase. However, a greater segment length is needed to obtain a homogeneous LC-phase. The poly(HPPA/HBA) copolyesters were also characterized by melt rheology. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1397-1405, 1998
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    Polymerization of acrylates by atom transfer radical polymerization. Homopolymerization of 2-hydroxyethyl acrylate (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1417-1424 
    Details
    ISSN: 0887-624X
    Keywords: 2-hydroxyethyl acrylate ; poly(2-hydroxyethyl acrylate) ; atom transfer radical polymerization (ATRP) ; controlled free radical polymerization ; MALDI-MS ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of atom transfer radical polymerization (ATRP) to the homopolymerization of 2-hydroxyethyl acrylate, a functional monomer, is reported. The polymerizations exhibit first-order kinetics, and molecular weights increase linearly with conversion. Polydispersities remain low throughout the polymerization (Mw/Mn ≈ 1.2). Reactions were conducted in bulk and in 1 : 1 (by volume) aqueous solution; the latter demonstrates the resilience of ATRP to protic media. Analysis of poly(2-hydroxyethyl acrylate) by MALDI-MS and 1H-NMR shows Mn,exp to be much closer to Mn,th than those observed by SEC using polystyrene standards. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1417-1424, 1998
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    Unbridged bivalent lanthanidocenes for isotactic and stereomultiblock polymerization of methyl methacrylate (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1599-1606 
    Details
    ISSN: 0887-624X
    Keywords: bivalent organolanthanides ; polymerization ; methyl methacrylate ; stereomultiblock polymer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bivalent organolanthanides with unbridged substituted indenyl or fluorenyl ligands (1-SiMe3Ind)2YTHF (I), (9-SiMe3Flu)2YTHF (II), were found to efficiently catalyze the stereoregular polymerization of methyl methacrylate. The microstructure of resultant polymers was shown to be dependent of a conformation that the ligands adopt at the polymerization temperature. The formation of isotactic rich PMMAs from complex II was proposed to be associated with the fluctuation of the 9-trimethylsilylfluorenyls around a C2 symmetric twisted-conformation. The formation of the multi(syndioPMMA-block-iso-PMMA) polymers from the mixture of rac- and meso-isomers of I was rationalized on the basis of competing conjugate addition and inversion of the metallocene conformation. Surprisingly, both rac- and meso-isomers of I were found to operate with similar activity and stereospecifity, although the stereospecific operation of the meso-form was not completely understandable. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1599-1606, 1998
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    Novel hydrogen-transfer polymerization of vinyl monomer derived from p-toluenesulfonyl isocyanate and acrylamide (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1491-1494 
    Details
    ISSN: 0887-624X
    Keywords: sulfonyl isocyanate ; acrylamide ; hydrogen-transfer polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 1 Ill.
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  • 49
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    p-Nitrophenol permeability and temperature characteristics of an acryloyl-L-proline methyl ester-based porous gel membrane (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1495-1500 
    Details
    ISSN: 0887-624X
    Keywords: acryloyl-L-proline methyl ester (A-ProOMe) ; methacryloyl-L-proline methyl ester (MA-ProOMe) ; porous gel membranes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermoresponsive porous gel membranes were synthesized by a simultaneously occurring process consisting of radiation-induced polymerization and crosslinking in aqueous solutions at various concentrations of acryloyl-L-proline methyl ester(A-ProOMe) without a crosslinker. Permeation of p-nitrophenol (PNP) through a thermoresponsive porous gel membrane obtained at a monomer concentration of 80% (w/w) drastically reduced around 14°C, the lower critical solution temperature (LCST) of linear poly(A-ProOMe) in water, from 0.60 × 10-3 cm/min at 10°C to no permeation at 18°C, accompanied by changes in both size and shape of pores associated with gel shrinkage. Moreover, it was found that porous gel membranes with a porosity of approximately 60% had a greater PNP permeability constant through porous gel membranes with mutually connected pores obtained at a monomer concentration of 50% (w/w) than individually supported pores obtained at a monomer concentration of 70% (w/w). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1495-1500, 1998
    Additional Material: 9 Ill.
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  • 50
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    Polymerization under a magnetic field. VI. Triplet dye-sensitized photopolymerization of acrylamide and methyl methacrylate (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1509-1513 
    Details
    ISSN: 0887-624X
    Keywords: methylene blue ; dye-sensitized photopolymerization ; magnetic field ; triplet state ; acrylamide ; methyl methacrylate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methylene blue sensitized photopolymerization of acrylamide (AM) and methyl methacrylate (MMA) using triethanolamine or the sodium salt of EDTA as a reducing agent has been investigated under the influence of a magnetic field (0-7.3 kG). There was no effect of the magnetic field (MF) on the polymerization of AM and MMA in aqueous medium. However, in the water-methanol mixture (1 : 1) the yield of polymer decreases and the molecular weight increases in both cases under MF. This has been explained on the basis of the triplet mechanism. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1509-1513, 1998
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    Porous monodisperse poly(divinylbenzene) microspheres by precipitation polymerization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1543-1551 
    Details
    ISSN: 0887-624X
    Keywords: polymer microspheres ; monodisperse ; crosslinked ; porosity ; porogen ; precipitation polymerization ; divinylbenzene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The precipitation polymerization of commercial divinylbenzene in acetonitrile containing up to 40 vol. % toluene or other cosolvents is shown to produce novel porous monodisperse poly(divinylbenzene) microspheres. These microspheres have diameters between 4 and 7 μm, total pore volumes of up to 0.52 cm3/g, and surface areas of up to 800 m2/g. As no surfactant nor stabilizer was used in the preparation of these particles, their surfaces are free of any such residues. The particles were slurry-packed into stainless steel columns for size exclusion chromatography evaluation, and the results show an exclusion limit at molecular weights of 500 g/mol. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1543-1551, 1998
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    (Diisopropylamido) bis (methylcyclopentadienyl) lanthanides as single-component initiators for polymerization of methyl methacrylate (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1593-1597 
    Details
    ISSN: 0887-624X
    Keywords: MMA ; polymerization ; (diisopropylamido)bis(methylcyclopentadienyl)lanthanides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It was first found that (diisopropylamido)bis(methylcyclopentadienyl)lanthanides (MeC5H4)2LnN(i-Pr)2(THF) (Ln = Yb (1), Er (2), Y (3)) exhibit extremely high catalytic activity in the polymerization of methyl methacrylate. The reactions can be carried out over a quite broad range of polymerization temperatures from -78 to 40°C. The catalytic activity of the complexes increases with an increase of ionic radii of the metal elements, i.e. Y 〉 Er 〉 Yb. The results of GPC (gel permeation chromatography) indicate that the number-average molecular weights (Mn) of polymers obtained exceed 100 × 103 and the molecular weight distribution (Mw/Mn) becomes broad with the increase of temperature. Furthermore highly syndiotactic PMMA (87.7%) can be obtained by lowering the reaction temperature to -78°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1593-1597, 1998
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    Preparation and properties of poly(styrene-co-maleic anhydride)/silica hybrid materials by the in situ sol-gel process (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1607-1613 
    Details
    ISSN: 0887-624X
    Keywords: sol-gel ; hybrid material ; poly(styrene-co-maleic anhydride) ; tetraethoxysilane ; (3-aminopropyl)triethoxysilane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(styrene-co-maleic anhydride)/silica hybrid material has been successfully prepared from styrene-maleic anhydride copolymer and tetraethoxysilane (TEOS) in the presence of a coupling agent (3-aminopropyl)triethoxysilane (APTES) by an in situ sol-gel process. It was observed that the gel time of sol-gel solution was dramatically influenced by the amount of APTES. The hybrid material exhibits optical transparency almost as good as both silica gel and the copolymer. The covalent bonds between organic and inorganic phases were introduced by the aminolysis reaction of the amino group with maleic anhydride units of copolymer to form a copolymer bearing trimethoxysilyl groups, which undergo hydrolytic polycondensation with TEOS. The differential scanning calorimetry (DSC) showed that the glass transition temperature of the hybrid materials increases with increasing of SiO2 composition. Photographs of scanning electron microscopy (SEM) and atomic force microscopy (AFM) inferred that the size of the inorganic particles in the hybrid materials was less than 20 nm. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1607-1613, 1998
    Additional Material: 8 Ill.
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    Influence of plasma treatment on the molar mass of poly(ethylene terephthalate) investigated by different chromatographic and spectroscopic methods (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1639-1648 
    Details
    ISSN: 0887-624X
    Keywords: poly(ethylene terephthalate) (PET) ; plasma ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of different types of low and atmospheric pressure plasma on poly(ethylene terephthalate) (PET) has been studied in terms of changes in molar mass and molar mass distribution. Apart from a variation of plasma gases (oxygen, helium) different types of plasma (microwave, radio frequency, corona discharge) were used for the plasma surface modification. The changes in molar mass and types of functional end groups of lower molar mass products were investigated by means of matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOFMS), whereas the high-molar mass fraction was analyzed by means of size-exclusion chromatography (SEC). The formation of crosslinked products during exposure to a helium plasma, which emits preponderately energy-rich and intense ultraviolet radiation, was proved by means of thermal field-flow fractionation (ThFFF). This method combined with a multiangle laser light scattering (MALLS) detector allows detection of weakly crosslinked polymers and microgels. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1639-1648, 1998
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  • 55
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    Synthesis and properties of poly(ether imide)s derived from 2,6-bis(3,4-dicarboxyphenoxy)naphthalene dianhydride and aromatic diamines (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1657-1665 
    Details
    ISSN: 0887-624X
    Keywords: 2,6-bis(3,4-dicarboxyphenoxy)naphthalene dianhydride ; poly(ether imide)s ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new naphthalene unit-containing bis(ether anhydride), 2,6-bis(3,4-dicarboxyphenoxy)naphthalene dianhydride, was synthesized in three steps starting from the nucleophilic nitrodisplacement reaction of 2,6-dihydroxynaphthalene and 4-nitrophthalonitrile in N,N-dimethylformamide (DMF) solution in the presence of potassium carbonate, followed by alkaline hydrolysis of the intermediate bis(ether dinitrile) and subsequent dehydration of the resulting bis(ether diacid). High-molar-mass aromatic poly(ether imide)s were prepared using a conventional two-step polymerization process from the bis(ether anhydride) and various aromatic diamines. The intermediate poly(ether amic acid)s had inherent viscosities of 0.65-2.03 dL/g. The films of poly(ether imide)s derived from two rigid diamines, i.e. p-phenylenediamine and benzidine, crystallized during the thermal imidization process. The other poly(ether imide)s belonged to amorphous materials and could be fabricated into transparent, flexible, and tough films. These aromatic poly(ether imide) films had yield strengths of 104-131 MPa, tensile strengths of 102-153 MPa, elongation to break of 8-87%, and initial moduli of 1.6-3.2 GPa. The glass transition temperatures (Tg's) of poly(ether imide)s were recorded in the range of 220-277°C depending on the nature of the diamine moiety. All polymers were stable up to 500°C, with 10% weight loss being recorded above 550°C in both air and nitrogen atmospheres. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1657-1665, 1998
    Additional Material: 2 Ill.
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    A simple method for the anionic polymerization of α-carbonyl acids in water (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1683-1683 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    Novel aromatic polyhydrazides and poly(amide-hydrazide)s based on “multiring” flexible dicarboxylic acids (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1847-1854 
    Details
    ISSN: 0887-624X
    Keywords: polyhydrazides ; poly-1,3,4-oxadiazoles ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two flexible dicarboxylic acid monomers, 4,4′-[isopropylidenebis(1,4-phenylene)dioxy]dibenzoic acid (1) and 4,4′-[hexafluoroisopropylidenebis(1,4-phenylene)-dioxy]dibenzoic acid (3), were synthesized from readily available compounds in two steps in high yields. High molecular-weight polyhydrazides and poly(amide-hydra-zide)s were directly prepared from dicarboxylic acids 1 and 3 with terephthalic dihydrazide (5), isophthalic dihydrazide (6), and p-aminobenzhydrazide (7) by the phosphorylation reaction by means of diphenyl phosphite (DPP) and pyridine in N-methyl-2-pyrrolidone (NMP)/LiCl, or prepared from the diacyl chlorides of 1 and 3 with the hydrazide monomers 5-7 by the low-temperature solution polycondensation in NMP/LiCl. Less favorable results were obtained when using triphenyl phosphite (TPP) instead of DPP in the direct polycondensation reactions. Except for those derived from terephthalic dihydrazide, the resulting polyhydrazides and poly(amide-hydrazide)s could be cast into colorless, flexible, and tough films with good tensile strengths. All the hydrazide polymers and copolymers are amorphous in nature and are readily soluble in various polar solvents such as NMP and dimethyl sulfoxide (DMSO). Their Tgs were recorded in the range of 162-198°C and could be thermally cyclodehydrated into the corresponding polyoxadiazoles and poly(amide-oxadiazole)s approximately in the region of 300-380°C, as evidenced by the DSC thermograms. The oxadiazole polymers and copolymers showed a dramatically decreased solubility and higher Tg when compared to their respective hydrazide prepolymers. They exhibited Tgs of 190-216°C and were stable up to 450°C in air or nitrogen. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1847-1854, 1998
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    Novel polyisobutylene/poly(dimethylsiloxane) bicomponent networks. I. Synthesis and characterization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1891-1899 
    Details
    ISSN: 0887-624X
    Keywords: polyisobutylene ; poly(dimethylsiloxane) ; hydrosilation ; bicomponent networks ; molecular weight between crosslinks ; network functionality ; sol fraction ; extractables ; model networks ; end-linking ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of novel polyisobutylene (PIB)/poly(dimethylsiloxane) (PDMS) bicomponent networks is described. The synthesis strategy (see Figure 1) was to prepare well-defined and -characterized allyl-tritelechelic polyisobutylenes [φ(PIB - C - C=C)3] and SiH-ditelechelic poly(dimethylsiloxanes) (HSi-PDMS-SiH) and then crosslink these moieties by hydrosilation. The φ(PIB - C - C=C)3 was prepared by living isobutylene polymerization followed by end-quenching with allyltrimethylsilane, whereas the HSi-PDMS-SiH was obtained by equilibrium polymerization of octamethylcyclotetrasiloxane and tetramethyldisiloxane. The detailed structures of the starting polymers were characterized by GPC and 1H-NMR spectroscopy. A series of PIB/PDMS bicomponent networks of varying compositions and average molecular weights between crosslinks (Mc) of ∼ 20,000 g/mol were assembled. Optimum crosslinking conditions were defined in terms of H2PtCl6 catalyst concentration, nature of solvent, time, temperature, and stoichiometry of ∼ CH2CH=CH2/∼SiH groups, allowing for the convenient synthesis of well-defined model bicomponent networks. Swelling studies and elemental analysis confirm the correctness of the synthetic strategy. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1891-1899, 1998
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    Novel polyisobutylene/poly(dimethylsiloxane) bicomponent networks. II. Network structure and property characterization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1901-1910 
    Details
    ISSN: 0887-624X
    Keywords: polyisobutylene ; poly(dimethylsiloxane) ; bicomponent networks ; network structure ; molecular weight between crosslinks ; network properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first part of this series concerned the synthesis of novel polyisobutylene (PIB)/poly(dimethylsiloxane) (PDMS) bicomponent networks; the present paper concerns the structure and property characterization of a series of bicomponent networks of varying compositions (PIB wt %/PDMS wt % = 92/8, 70/30, 50/50, 35/65) having average molecular weights between crosslinks (Mc) of ˜ 20,000 g/mol. According to network structure analysis by uniaxial equilibrium stress-strain measurements, the experimental Mc's are in excellent agreement with theoretical values. Hydrosilation end-linking efficiency was quantitated by the amount of sol and functional group analysis by 1H-NMR spectroscopy. NMR evidence indicates double-bond isomerization during hydrosilation. Network compositions by elemental analysis together with the low sol fractions indicate efficient crosslinking. These data suggest highly efficient network formation and well-defined bicomponent network structures. While PIB and PDMS showed Tg's at -72 and -124°C, respectively, the bicomponent network did not exhibit clearly discernible phase transitions. The heat stability of bicomponent networks increased slightly with increasing PDMS content showing initial (10%) degradation temperatures at ˜ 380°C in nitrogen and ˜ 320°C in air. Tensile strengths and elongations were dependent on composition and varied in the 0.6-3.8 MPa and 600-1100% ranges, respectively. The swelling behavior was not much affected by composition. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1901-1910, 1998
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    Copolymerization of carbon monoxide and norbornene derivatives with ester groups by palladium catalyst (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1785-1790 
    Details
    ISSN: 0887-624X
    Keywords: carbon monoxide ; norbornene ester ; glass transition temperature ; palladium catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article we will discuss the synthesis of the new copolymers of norbornene derivatives with an ester group and carbon monoxide, using Pd(CH3CN)4(BF4)2 as a catalyst and 2,2′-bipyridine as a ligand in nitromethane/methanol at 60°C. Elementary analysis, infrared spectra, and NMR spectra indicated that copolymers contain ketone, ester, and bicyclic structures. Methanol functions as the coinitiator and chain transfer agent in copolymerization. A decrease in the molar ratio of [CH3OH]/[Pd] caused an increase in molecular weight and a decrease in yield of the copolymer. The number-average molecular weight of copolymers (Mn) ranged from 3800 to 5300, and the glass transition temperature (Tg) ranged from -32 to 117°C. Thermal analysis revealed that both T10%d and Tmaxd exceeded 180 and 230°C, respectively. Linear long-chain substituents such as n-C11H23C(O)—O—CH2— drastically reduced Tg to a value of -32°C. In general, copolymers having a longer linear side-chain substituents of ester on norbornene have a more desirable solubility. Moreover, X-ray diffraction demonstrated that the degree of crystallinity decreases with an increasing length of side chain substituents. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1785-1790, 1998
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    LC-polyimides XXXIV. Noncrystalline thermotropic copoly(ester-imide)s based on PET (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1813-1820 
    Details
    ISSN: 0887-624X
    Keywords: poly(ester-imide)s ; poly(ethylene terephthalate) ; transesterification, nematic phase ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four series of copoly(ester-imide)s (co-PEIs) were prepared by transesterification of poly(ethylene terephthalate), PET, with N-(4-carboxyphenyl)trimellitimide and an acetylated diphenol. Methylhydroquinone, tert. butylhydroquinone, phenylhydroquinone, and 2,7-dihydroxynaphthalene were used as diphenols. The chemical structures of these co-PEIs were characterized by chemical analyses, 1H-, and 13C-NMR spectra. A low degree of crystallinity was observed when the PET content was above 85% mol %. Between 60 and 80 mol % PET all co-PEIs are biphasic, whereas below 60 mol % the co-PEIs form a homogeneous nematic melt and below the glass transition temperature (Tg) a nematic glass. The Tgs vary continously with the molar composition but the mechanical properties drop sharply when the nematic phase changes to an isotropic one. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1813-1820, 1998
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    Morphology and grafting of oxazoline-functional polymer particles with various carboxylic acids (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1821-1827 
    Details
    ISSN: 0887-624X
    Keywords: morphology ; grafting ; oxazoline-functionalized polymer particles ; carbolic acids ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxazoline-functionalized, crosslinked PMMA-particles, prepared by free radical nonaqueous dispersion polymerization, were grafted with n-decanoic acid and carboxylic acid-terminated polystyrene. Oxazoline groups, separated by an alkylspacer from the PMMA backbone, showed enhanced mobility with respect to the backbone, as evaluated by solid-state NMR spectroscopy using a dipolar filter. As a function of molecular mass of the carboxylic acid, the oxazoline conversion varied from 70 mol % for n-decanoic acid to 1% for monocarboxylate-terminated polystyrene CT-PS with Mn: 15,900 g/mol. Morphological studies, performed by TEM, showed that reaction with acid terminated polystyrene results exclusively in interfacial grafting at the particle surface. At low grafting levels a raspberry-like morphology was obtained, whereas grafting levels exceeding 14 wt % CT-PS resulted in core-shell morphology. Core-shell morphology was also verified by static light scattering using toluene solvent, which is isorefractive to the PMMA core. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1821-1827, 1998
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    Aminolysis kinetics of model and polymer-bound anhydride moieties in low- and high-viscosity media (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1573-1582 
    Details
    ISSN: 0887-624X
    Keywords: amic acid ; secondary amine ; maleic anhydride ; melt reaction kinetics ; model compounds ; polymer-bound functional groups ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study examines the legitimacy of using the reaction kinetics of low molecular weight model compounds in solution to predict the chemical kinetics of polymer-bound species in a homogeneous melt. The reaction under study takes place between an aliphatic secondary amine, diisooctadecylamine (DiOA), and a 5-membered anhydride ring, saturated maleic anhydride (MA), forming an amic acid product. The MA species was present as a pendant graft on either a model compound, dodecane-g-(maleic anhydride) (dodecane-g-MA), or a polymer chain, linear low-density polyethylene-g-(maleic anhydride) (LLDPE-g-MA). Pseudo-second-order kinetics of the anhydride consumption are followed by infrared spectroscopy, either in situ in dodecane solution or by scanning frozen film samples taken from a linear low-density polyethylene melt. It was found that the LLDPE-g-MA/DiOA system reacted at a slightly slower rate than the dodecane-g-MA/DiOA system in the low-viscosity solution at 140°C. In the melt, the dodecane-g-MA/DiOA system experienced a small decrease in the overall reaction rate compared to the same reaction carried out in dodecane. However, the LLDPE-g-MA/DiOA system underwent a 65% decrease in the observed second-order rate constant on going from a solution to the melt. To explain these phenomena, the effects of diffusion, miscibility, and chain entanglements in the melt are examined here. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1573-1582, 1998
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    New polymer syntheses. XC. A-B-A triblock copolymers with hyperbranched polyester A-blocks (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 31-38 
    Details
    ISSN: 0887-624X
    Keywords: triblock copolymers ; polycondensations ; telechelic character ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Telechelic oligo(ether-ketone)s containing two trimethylsiloxy end groups and one methyl group per repeating unit were prepared by polycondensation of 4-fluoro-2′-methyl-4′-(trimethylsiloxy)benzophenone. The telechelic character was achieved by cocondensation of a small amount of silylated bisphenol-P. The end groups of the silylated oligo(ether-ketone)s were acetylated by means of acetyl chloride. On the basis of 1H-NMR end group analyses two samples of α,ω-bis(acetoxy) oligo(ether-ketone)s with DP = 14 and DP ∼ 28 were obtained. These oligo(ether-ketone)s and a 70 or 140 fold molar amount of silylated 3,5-bis(acetoxy)benzoic acid were polycondensed at 270°C in bulk. The resulting A-B-A triblock copolymers were fractionated by dissolution in tetrahydrofuran. In three out of four experiments a small fraction of precipitated material rich in oligo(ether-ketone) was isolated. The purified triblock copolymers were characterized by inherent viscosities and NMR spectra. For those samples containing the long oligo(ether-ketone) block a low degree of crystallinity was observed after annealing. Four additional polycondensations were conducted with an initial reaction temperature of 290°C. In this way a completely soluble and amorphous triblock copolymer was obtained. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 31-38, 1998
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    Liquid crystalline epoxy resins by polyaddition of diglycidyl ether of 4,4′-dihydroxybiphenyl and difunctional aromatic compounds (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 21-29 
    Details
    ISSN: 0887-624X
    Keywords: liquid crystalline polymers ; epoxy resins ; thermotropic ; polymer chain extension ; catalytic polyaddition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work is a continuation of the authors' earlier investigations of liquid crystalline epoxy resins prepared from diglycidyl ether of 4,4′-dihydroxybiphenyl (DGE-DHBP), which was used as a mesogenic agent, and aliphatic dicarboxylic compounds, which were used as flexible spacers. In this paper, the synthesis and characterization of liquid crystalline epoxy resins, prepared from DGE-DHBP and difunctional aromatic compounds are described. Three series of liquid crystalline epoxy resins were prepared by chain extension of DGE-DHBP with isomeric hydroxybenzoic and benzenedicarboxylic acids as well as diphenols. An isophthalic-terminated polyether was applied to decrease the temperature of phase transitions. The syntheses were carried out by catalytic polyaddition in the melt. Triphenylphosphine was applied as the catalyst. The resulting epoxy resins were investigated by DSC, polarizing microscope as well as by X-ray and IR spectroscopy. The phase transition temperatures and the type of mesophase of the resulting products depend on the character of the functional groups in the chain extender and on the position of the functional groups in the aromatic ring. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 21-29, 1998
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    Preparation and properties of new soluble aromatic polyimides from 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride and aromatic diamines (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2021-2027 
    Details
    ISSN: 0887-624X
    Keywords: 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride ; aromatic polyimides ; solubility ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new aromatic tetracarboxylic dianhydride having a crank and twisted noncoplannar structure, 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, was synthesized by the reaction of 4-nitrophthalonitrile with biphenyl-2,2′-diol, followed by hydrolysis and cyclodehydration. The biphenyl-2,2′-diyl-containing aromatic polyimides having inherent viscosities up to 0.66 dL/g were obtained by the conventional two-step procedure starting from the dianhydride monomer and various aromatic diamines. Most of the polyimides were readily soluble in amide-type solvents such as N,N-dimethylacetamide and N-methyl-2-pyrrolidone. The aromatic polyimides had glass transition temperatures in the range of 205-242°C, and began to lose weight around 415°C, with 10% weight loss being recorded at about 500°C in air. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2021-2027, 1998
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    Studies of lipase-catalyzed polyesterification of an unactivated diacid/diol system (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2069-2079 
    Details
    ISSN: 0887-624X
    Keywords: Candida antarctica lipase ; Novozym 435® ; polyester ; enzymatic polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preliminary enzymatic polymerization studies in the simple stoichiometric adipic acid/butane-1,4-diol system using lipase B from Candida antarctica, immobilized as Novozym 435®, suggest that in solvent-free conditions a step-growth mechanism operates involving the sequential addition of an AB synthon by esterification mode only. Conversely, in toluene as solvent there is a change to the more facile transesterification mode in line with the conventional polyesterification procedure, pointing to a change in specificity of the lipase. Evidence is drawn from qualitative studies using a series of synthetic intermediates, enabling authentication of product mixtures together with an indication of the comparative reactivity of species along the proposed reaction pathway. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2069-2080, 1998
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    Mechanical properties of blends of PAMAM dendrimers with poly(vinyl chloride) and poly(vinyl acetate) (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2111-2117 
    Details
    ISSN: 0887-624X
    Keywords: dendritic polymer ; blends ; coatings ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hybrid blends of poly(amidoamine) PAMAM dendrimers with two linear high polymers, poly(vinyl chloride), PVC, and poly(vinyl acetate), PVAc, are reported. The interaction between the blend components was studied using dynamic mechanical analysis, xenon nuclear magnetic resonance (NMR) spectroscopy, and tensile property measurements. The data suggest a much higher degree of interaction between components of PVAc-containing blends compared to those containing PVC. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2111-2117, 1998
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    Side chain liquid crystal polyurethanes with azobenzene mesogenic moieties: Influence of spacer length on hydrogen bonding at different temperatures (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2135-2146 
    Details
    ISSN: 0887-624X
    Keywords: SCLC polyurethanes ; azobenzene mesogenic group ; alkyl spacer ; bilayer smectic phases ; hydrogen bonding ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of side chain liquid crystal polyurethanes (CnCNPs), in which the spacer length was varied from 2 to 12 methylene units, were synthesized by the addition polymerization of α-[bis(2-hydroxyethyl)amino]-ω-(4-cyanoazobenzene-4′-oxy)alkanes (CnCN-diols) with hexamethylene diisocyanate. The liquid crystalline properties of CnCNPs were characterized by means of differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. Polyurethanes with spacer length 4 or higher exhibited mesomophic properties. C4CNP and C5CNP exhibited an enantiotropic nematic mesophase, while C6-C12CNPs exhibited enantiotropic bilayer smectic mesophases. CnCNPs have a high tendency to crystallize; crystallization is kinetically controlled. Polyurethane's backbone crystallization is closely related to hydrogen bonding. To establish the role of hydrogen bonding in mesophase formation as well as crystallization, Fourier transform infrared spectroscopy studies of CnCNPs were carried out at different temperatures focusing on H-bonds between the N—H and C=O groups of the urethane backbone. With increasing temperature, C=O and N—H stretching bands were evenly shifted to higher wavenumbers, with two exceptions (C4CNP and C5CNP) discussed in detail in the text. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2135-2146, 1998
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    Initiation mechanisms in free radical polymerization: Competitive reaction of cyanoisopropyl radicals with styrene and acrylonitrile (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2169-2176 
    Details
    ISSN: 0887-624X
    Keywords: free radical ; initiation ; styrene ; acrylonitrile ; copolymerization ; nitroxide trapping ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The competitive reactions of cyanoisopropyl radicals with the mixed monomers styrene and acrylonitrile have been investigated using the nitroxide radical trapping technique. When the trap concentration is kept low, second, third, and even fourth generation (in terms of successive monomer addition) carbon radicals have been observed as trapped products. The ratio of rate constants for the addition of styrene and acrylonitrile to cyanoisopropyl radicals is 2.7 at 75°C and 5.3 at 105°C. These values are compared with the ratios for reactions of these two monomers with a number of other radicals and discussed in terms of the polarities of the radicals and monomers. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2169-2176, 1998
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    Synthesis and characterization of new poly(amide-imide)s from 1,4-bis(4-trimellitimidophenoxy)-2-tert-butylbenzene with various diamines (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2301-2307 
    Details
    ISSN: 0887-624X
    Keywords: 1,4-bis(4-trimellitimidophenoxy)-2-tert-butylbenzene (BTTB) ; direct polycondensation ; poly(amide-imide)s ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New poly(amide-imide)s were prepared from a diimide-dicarboxylic acid, 1,4-bis(4-trimellitimidophenoxy)-2-tert-butylbenzene (BTTB), with various diamines by the direct polycondensation in N-methyl-2-pyrrolidinone (NMP) using triphenyl phosphite and pyridine as condensing agents. The new diimide-dicarboxylic acid BTTB containing an ether linkage and tert-butyl substituent was synthesized by the condensation reaction of 1,4-bis(4-aminophenoxy)-2-tert-butylbenzene with trimellitic anhydride. All the polymers were obtained in quantitative yields with inherent viscosities of 0.62-1.06 dL g-1. The polymers were amorphous, and most of them were readily soluble in aprotic polar solvents such as NMP, N,N-dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF), as well as in less polar solvents such as dimethyl sulfoxide (DMSO), m-cresol, pyridine, and γ-butyrolactone, and also even in tetrahydrofuran. The glass transition temperatures of the polymers were determined by DSC method, and they were in the range of 238-279°C. These polymers were stable up to 408-449°C in air and 451-483°C in nitrogen and lose 10% weight in the range of 479-525°C in air and 480-528°C in nitrogen atmosphere. The polymer films had a tensile strength range of 71-115 MPa, an elongation at break range of 4-14%, and a tensile modulus range of 2.3-3.1 GPa. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2301-2307, 1998
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    Synthesis and surface characterization of heparin-immobilized polyetherurethanes (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2331-2338 
    Details
    ISSN: 0887-624X
    Keywords: poly(ether urethane) ; surface modification ; heparin immobilization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel poly(ether urethanes) containing diester groups in the side chains (PU) were synthesized from 4,4′-diphenylmethyl diisocyanate, polytetramethylene glycol, and diethyl bis(hydroxymethyl)malonate as a chain extender. The surface modification of the PU film was carried out by a hydrolysis reaction, poly(ethylene oxide) (PEO) grafting, and heparin immobilization, and the surface-modified PUs were then characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), and a contact angle goniometer. The concentration of carboxylic acid groups introduced on the PU surfaces as determined by the rhodamine interaction method was 61 nmol/cm2 when treated with 4N NaOH/methanol (1 : 2 v/v) for 30 min and subsequently with a citric acid-methanolic aqueous solution. The amounts of heparin coupled to the carboxyl groups on the PU surfaces and to the terminus amino groups on the PU-PEO were 0.92 and 0.84 μ g/cm2, respectively. There was almost no heparin released from the immobilized surface of a physiological solution for 100 h, thereby indicating the strong stability of immobilized heparin. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2331-2338, 1998
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    Synthesis and characterization of new aromatic polyesters and a polyether derived from 2,2-bis(4-hydroxyphenyl)-1,2-diphenylethanone (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2229-2235 
    Details
    ISSN: 0887-624X
    Keywords: polyarylates ; aromatic polyether ; 2,2-bis(4-hydroxyphenyl)-1,2-diphenylethanone ; solubility ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New polyarylates having benzopinacolone units were synthesized from 2,2-bis(4-hydroxyphenyl)-1,2-diphenylethanone and aromatic dicarboxylic acid chlorides. The polymers having an inherent viscosity of 0.71-0.94 dL/g were obtained by the two-phase method using toluene as an organic solvent. The polymers were easily soluble in various organic solvents and had high glass transition temperatures in the range of 200-240°C. An aromatic polyether having benzopinacolone unit was also prepared. However, its inherent viscosity was low because of the occurrence of a side reaction. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2229-2235, 1998
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    Preparation of plasma-grafted polymer membranes and their morphology and pervaporation properties toward benzene/cyclohexane mixtures (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2247-2259 
    Details
    ISSN: 0887-624X
    Keywords: pervaporation ; plasma graft polymerization ; membrane ; glycidyl methacrylate ; morphology ; porous polyethylene ; benzene/cyclohexane separation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Composite membranes were prepared by plasma-induced graft polymerization of vinyl monomers onto porous substrates of high density polyethylene, and the relationship between the polymerization conditions and morphological structure and pervaporation performance toward benzene/cyclohexane mixtures was investigated in detail. The morphological structures of the plasma-grafted membranes depended on the monomer reactivity, plasma treatment manner, and graft polymerization conditions. Pervaporation properties were closely related to the graft monomers and the morphological structures. The poly(glycidyl methacrylate)-grafted membranes prepared by homogeneous both sides plasma treatment and under mild polymerization conditions showed the highest pervaporation performance with a permeation flux of 0.3 kg/(m2 h) and separation factor of 22 at 60 wt % benzene and 70°C. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2247-2259, 1998
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    Polymerization of olefins with a novel dinuclear ansa-zirconocene catalyst having a biphenyl bridge (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2269-2274 
    Details
    ISSN: 0887-624X
    Keywords: dinuclear ansa-zirconocene catalyst ; diastereomers ; biphenyl and phenyl ligands ; polymerization of ethene and propene ; copolymerization of ethene and 1-octene ; thermal stability of active species ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both the rac- and meso-dinuclear ansa-zirconocene catalysts (μ-C12H8{[SiPh(Ind)2]ZrCl2}2) were prepared by a coupling reaction between 2 equiv of diindenylphenylchlorosilane (rac- and meso-isomers) and 1 equiv of p-dilithiobiphenyl in diethyl ether at -80°C, followed by a successive reaction with ZrCl4 · 2THF in THF at -78°C. Polymerizations of ethene and propene were conducted in a 1 dm3 high-pressure glass reactor equipped with a mechanical stirrer at 60, 80, 100, 120, and 150°C using methylalumoxane (MAO) as cocatalyst and toluene or decahydronaphthalene as the solvent. Copolymerization of ethene and 1-octene was also checked in brief. For ethene polymerization, the meso-catalyst was found to be more active, which displayed an extremely high activity to give linear polyethene with a high molecular weight and a narrow molar mass distribution (MMD). The apparent activity increased monotonously with rising polymerization temperature from 60°C up to 150°C, indicating that the active species are stable even at a high temperature. On the other hand, both the rac- and meso-catalysts showed very poor activities for propene polymerization. However, copolymerization of ethene and 1-octene proceeded at a high speed. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2269-2274, 1998
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    Spectral, thermal, and electrical properties of poly(o- and m-toluidine)-polystyrene blends prepared by emulsion pathway (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2291-2299 
    Details
    ISSN: 0887-624X
    Keywords: poly(o-toluidine) ; (POT) ; poly(m-toluidine) ; (PMT) ; polystyrene (PSt) ; blends ; emulsion pathway ; spectroscopy ; thermal stability ; conductivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conducting poly(o-toluidine) (POT) and poly(m-toluidine) (PMT) blends containing 10, 30, 50, 70, and 90 % wt/wt of polystyrene (PSt) were prepared by employing a two-step emulsion pathway. The bands characteristic of both polystyrene and POT/PMT are present in the IR spectra of POT-PSt and PMT-PSt blends. The UV-visible spectra of POT-PSt and PMT-PSt blends exhibit two bands around 313 and 610 nm, confirming that some amount of POT/PMT base is present in the blends. The EPR parameters such as line width and spin concentration reveal the presence of POT/PMT salt in the respective blends. The TGA, DTA, and DSC results suggest a higher thermal stability for the POT and PMT blends than that for the respective salts. The conductivity values of POT(70)-PSt(30) and POT(90)-PSt(10) blends are almost the same (1.1 × 10-2 and 1.3 × 10-2 S cm-1, respectively) and these values are very close to that of pure POT salt, suggesting that POT can be blended with up to 30% wt/wt of PSt to improve its mechanical properties without a significant drop in its conductivity. The conductivity values of PMT-PSt blends are lower than those of the corresponding POT-PSt blends by two to three orders of magnitude, indicating that POT is a better system than PMT to prepare blends by this method. The dielectric constant and tan δ values of the blends increase with the amount POT/PMT and are greater than that of polystyrene. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2291-2299, 1998
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    Characterization and degradation of the poly(methylphenylsiloxane)-poly(methyl methacrylate) graft copolymer (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2521-2530 
    Details
    ISSN: 0887-624X
    Keywords: poly(methylphenylsiloxane) ; poly(methyl methacrylate) ; graft copolymer ; spin-spin relaxation ; degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(methylphenylsiloxane)-poly(methyl methacrylate) graft copolymers (PSXE-g-PMMA) were prepared by condensation reaction of poly(methylphenylsiloxane)-containing epoxy resin (PSXE) with carboxyl-terminated poly(methyl methacrylate) (PMMA), and they were characterized by gel permeation chromatography (GPC), infrared (IR), and 29Si and 13C nuclear magnetic resonance (NMR). The microstructure of the PSXE-g-PMMA graft copolymer was investigated by proton spin-spin relaxation T2 measurements. The thermal stability and apparent activation energy for thermal degradation of these copolymers were studied by thermogravimetry and compared with unmodified PMMA. The incorporation of poly(methylphenylsiloxane) segments in graft copolymers improved thermal stability of PMMA and enhanced the activation energy for thermal degradation of PMMA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2521-2530, 1998
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    Amine-linked thioxanthones as water-compatible photoinitiators (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2563-2570 
    Details
    ISSN: 0887-624X
    Keywords: thioxanthone derivatives ; water-compatible photoinitiator ; absorption spectrum ; fluorescence ; photopolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six amine-linked thioxanthones, i.e., 2-(2-hydroxy-3-[bis(2-hydroxyethyl)amino]propoxy)thioxanthone (HAPTX) and its 4-methyl, 1,3-dimethyl, 1,4-dimethyl, 3,4-dimethyl, and 1,3,4-trimethyl substituted derivatives, were synthesized as water-compatible photoinitiators and identified with FTIR, MS, NMR, and elementary analysis. The absorption and fluorescence properties were studied. Their photoinitiating polymerization efficiencies were tested with a recording dilatometer utilizing acrylamide as monomer in aqueous solution. The results show that the six amine-linked thioxanthones can independently initiate acrylamide polymerization efficiently without additional external amines as co-initiators. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2563-2570, 1998
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    Oxidative polymerization of phenylenediamines catalyzed by horseradish peroxidase (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2593-2600 
    Details
    ISSN: 0887-624X
    Keywords: phenylenediamine ; oxidative polymerization ; enzyme ; horseradish peroxidase ; CD spectrum ; organic solvent ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ortho-, meta-, and para-phenylenediamines were polymerized using hydrogen peroxide as an oxidant and horseradish peroxidase as a catalyst in mixed solvents of 1,4-dioxane and water. The yield of the polymers was strongly dependent on solvent composition, and maximum yields were obtained at 15-30% 1,4-dioxane. The analysis of circular dichroic spectra of the enzyme suggested that enzyme structure was significantly modified at high 1,4-dioxane contents, which may be responsible for the decrease of catalytic activity of the enzyme. On the basis of IR and electronic spectra of the polymers, it was considered that o- and p-phenylenediamine polymers retain disubstituted benzene nuclei, which suggests that the polymerization proceeded mainly via N - N coupling. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2593-2600, 1998
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    Synthesis of alkoxyamine initiators for controlled radical polymerization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2667-2668 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 81
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    Syntheses and properties of liquid crystalline N-substituted pyrroles and their polymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2691-2698 
    Details
    ISSN: 0887-624X
    Keywords: N-substituted pyrrole ; liquid crystalline polymer ; polypyrrole ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three liquid crystalline N-substituted pyrroles were synthesized from 6-(1-pyrrolyl)hexanol with phenolic derivatives having a mesogenic core of cyclohexylbenzene or biphenyl by Mitsunobu reaction. These pyrroles had two anodic peaks at 1.4 and 1.8 V (vs. SCE). The former was due to an oxidation of the pyrrole moiety and the latter was due to an oxidation of the mesogenic moiety. These pyrrole monomers were polymerized by electrochemical and chemical methods. The potentiostatic method and the chemical method using FeCl3 gave a soluble and fusible polymer, respectively. A polymer having a mesogenic core of cyclohexyl benzene obtained by the chemical method and a polymer having a mesogenic core of biphenylketone obtained by the potentiostatic method had a liquid-crystalline phase. The phase was identified as smectic A by polarizing microscopy and XRD analysis. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2691-2698, 1998
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  • 82
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    Effect of the initiator absorbance on the transition-metal complex photoinitiated polymerization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 207-208 
    Details
    ISSN: 0887-624X
    Keywords: photoinitiated polymerization ; initiator absorbance ; metal complex ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 1 Ill.
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  • 83
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    Controlled thermal degradation of polystyrene leading to selective formation of end-reactive oligomers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 209-213 
    Details
    ISSN: 0887-624X
    Keywords: end-reactive oligomer ; terminal vinylidene ; thermal degradation ; polystyrene ; temperature dependence ; chemical recycle ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 1 Ill.
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  • 84
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    Synthesis and evaluation of novel polyimides derived from spirobichroman diether anhydride (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 215-215 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 1 Tab.
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  • 85
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    Synthesis and characterization of polysilabutane having oligo(oxyethylene)phenyl groups on the silicon atom (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 225-231 
    Details
    ISSN: 0887-624X
    Keywords: silacyclobutane ; polysilabutane ; oligooxyethylene ; polycarbosilane ; anionic polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new class of polar polysilabutanes with mono- or tri-(oxyethylene)phenyl groups on the silicon atom have been synthesized by anionic polymerization of silacyclobutanes having ω-(t-butyldimethylsilyl-protected) mono- or tri-(oxyethylene)phenyl groups and subsequent deprotection of the silyl groups. The monomers were synthesized by treatment of 1,1-dichlorosilacyclobutane with ω-(t-butyldimethylsilyl-protected) mono- or tri-(oxyethylene)phenyl Grignard reagents. Anionic polymerization of silacyclobutane was performed with butyllithium initiator in THF. t-Butyldimethylsilyl-protecting groups at polymer pendant groups were hydrolyzed with tetrabutyl ammonium fluoride in water-containing THF. The obtained polysilabutanes were soluble in a polar organic solvent such as methanol, and their mass distributions were analysed by matrix-assisted laser-desorption-ionization mass spectrometry (MALDI TOF MS). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 225-231, 1998
    Additional Material: 2 Ill.
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  • 86
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    Ablation characteristics of silicone insulation (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 233-239 
    Details
    ISSN: 0887-624X
    Keywords: silicone rubber ; insulation ; ablation ; thermal decomposition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ablation characteristics of silicone insulation were examined in an induced air combustion chamber and by thermogravimetric analysis. The rate of ablation increased with the combustion pressure. Although the flame temperature was less effective in increasing the ablation rate, the ablation rate below 1160 K was much smaller than expected. The decomposition kinetics of the silicone insulation was significantly altered at this temperature range. The stability of the char layer was much higher below approximately 1000 K. Since the lower ablation rate was obtained in higher mass flow rate condition, the heat input from the boundary layer to the insulation surface was decreased at this condition. The expended insulation consisted of a virgin zone, reaction zone, and char layer. These degraded materials were generated at relatively narrow temperature ranges. The char layer maintained a silicone backbone structure even though it experienced severe conditions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 233-239, 1998
    Additional Material: 9 Ill.
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  • 87
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    Pressure-induced cis to trans isomerization of aromatic polyacetylenes prepared using a Rh complex catalyst: A control of π-conjugation length (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 217-223 
    Details
    ISSN: 0887-624X
    Keywords: aromatic polyacetylene ; Rh complex catalyst ; cis-transoid ; pressure ; isomerization ; solitons ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study reports that stereospecific polymerization of aromatic acetylenes, e.g., p-methoxyphenylacetylene (pMOPA) and p-ethoxyphenylacetylene (pEOPA)was successfully performed to give polyacetylene selectively bearing cis-transoid forms in high yield when a Rh complex catalyst, [Rh(norbornadiene)Cl]2 was used in the presence of triethylamine as the polymerization solvent together with a detailed characterization of the resulting polymers, before and after compression. Compression of these polymers induced a cis-trans isomerization at room temperature under vacuum even in the solid state. Based on data collected before and after compression it is estimated that the trans conjugated length, (C=C)n, produced as a result of the compression is n = 26 for PpMOPA and n = 40 for PpEOPA polymers, respectively. We further found that g values in the ESR spectra of the pristine polymer were shifted to higher magnetic field by compression, indicating that unpaired electrons called solitons are stabilized in the trans conjugation length as mobile electrons, although in the pristine polymers the unpaired electrons are stabilized in the less conjugated chain, showing large g value, suggesting a magnetic interaction between oxygen in the alkoxy group of phenyl moiety and unpaired electrons in the cis form. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 217-223, 1998
    Additional Material: 4 Ill.
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  • 88
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    Electron photoejection and its application in studies of electron transfers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. v 
    Details
    ISSN: 0887-624X
    Keywords: electron photoejection ; electron transfer ; radical anion disproportionation ; initiation ; anionic polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The principle of the electron photoejection technique is explained. This approach leads to the formation of transient spectra of unstable intermediates, allowing their recording and providing their extinction coefficients. Moreover, it permits determination of their electron affinities and the rates of their reactions, whether spontaneous or with some added substrates. Application of this technique to studies of disproportionation of radical anions has been most profitable. It led to the determination of the forward and backward rate constants of disproportionation of a variety of radical anions, and to discovery and quantification of some subtle features of these reactions. The electron photoejection technique provided the data characterizing the electron transfer initiation of anionic polymerization and clarified some of its features. Other opportunities provided by the electron photoejection in studies of electron transfer processes are suggested. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: v-xiii, 1998
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  • 89
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    Homo- and copolymerization of butadiene and styrene with neodymium tricarboxylate catalysts (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 241-247 
    Details
    ISSN: 0887-624X
    Keywords: neodymium tricarboxylate ; polymerization of butadiene or styrene ; copolymerization of butadiene and styrene ; cis-1,4 polymerization mechanism ; back-biting coordination model ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homo- and copolymerizations of butadiene (BD) and styrene (St) with rare-earth metal catalysts, including the most active neodymium (Nd)-based catalysts, have been examined, and the cis-1,4 polymerization mechanism was investigated by the diad analysis of copolymers. Polymerization activity of BD was markedly affected not only by the ligands of the catalysts but also by the central rare-earth metals, whereas that of St was mainly affected by the ligands. In the series of Nd-based catalysts [Nd(OCOR)3:R = CF3, CCl3, CHCl2, CH2Cl, CH3], Nd(OCOCCl3)3 gave a maximum polymerization activity of BD, which decreased with increasing or decreasing the pKa value of the ligands. This tendency was different from that for Gd(OCOR)3 catalysts, where the CF3 derivative led to the highest polymerization activity of BD. For the polymerization of St and its copolymerization with BD, the maximum activities were attained at R = CCl3 for both Nd- and Gd-based catalysts. The copolymerization of BD and St with Nd(OCOCCl3)3 catalyst was also carried out at various monomer feed ratios, to evaluate the monomer reactivity ratios as rBD = 5.66 and rSt = 0.86. The cis-1,4 content in BD unit decreased with increasing St content in copolymers. From the diad analysis of copolymers, it was indicated that Nd(OCOCCl3)3 catalyst controls the cis-1,4 structure of the BD unit by a back-biting coordination of the penultimate BD unit. Furthermore, the long range coordination of polymer chain by the neodymium catalyst was suggested to assist the cis-1,4 polymerization. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 241-247, 1998
    Additional Material: 8 Ill.
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  • 90
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    Synthesis of polysulfonates containing reactive pendant chloromethyl groups by the polyaddition of bisepoxides with disulfonyl chlorides (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 249-256 
    Details
    ISSN: 0887-624X
    Keywords: polysulfonate ; reactive chloromethyl groups ; polyaddition ; bisepoxide ; disulfonyl chloride ; quaternary onium salt ; catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polysulfonates with reactive pendant chloromethyl groups were synthesized by polyadditions of bisepoxides with disulfonyl chlorides. The polyaddition of bisphenol A diglycidyl ether (BPGE) with m-benzene disulfonyl chloride (m-BDSC) occurred in anisole without any catalyst at 130°C for 24 h. However, polymer with high molecular weight was not obtained. On the other hand, the polyadditions of BPGE with m-BDSC proceeded very smoothly with high yield (81-91%) to give polymers with relatively high molecular weights in anisole at 130°C for 24 h when quaternary phosphonium salts were used as catalysts. The polyaddition was also enhanced by the addition of certain crown ether complexes. However, the catalytic activity of these compounds was less than those of quaternary phosphonium salts. Furthermore, polyadditions of certain bisepoxides with disulfonyl chlorides were also carried out to produce the corresponding polymers under the same reaction conditions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 249-256, 1998
    Additional Material: 4 Ill.
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  • 91
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    Ring-opening polymerization of cyclic carbonates by alcohol-acid catalyst (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2463-2471 
    Details
    ISSN: 0887-624X
    Keywords: ring-opening reaction ; ring-opening polymerization ; alcohol ; cyclic carbonate ; activated monomer mechanism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ring-opening reactions of 1,3-dioxepan-2-one (1) and 1,3-dioxan-2-one (2) with several alcohols were examined. The reactions proceeded without trifluoroacetic acid (TFA) in low conversions, while they proceeded smoothly with TFA to afford the ring-opened adducts and oligomers. Ring-opening polymerizations of 1 and 2 were also carried out by alcohol-acid catalysts to afford the corresponding polycarbonates (Mn = 2500-6800). The molecular weights increased with increase of the conversions of 1 and 2. The observed polymerization rates of 1 and 2 were determined as 24.4 × 10-6 and 0.8 × 10-6 s-1, respectively. Mechanistic aspects were studied by NMR spectroscopy. The methylene protons α and β to the carbonate moieties shifted to lower fields in 0.06-0.11 ppm in the 1H-NMR spectra by the addition of TFA. Downfield shifts of the carbonyl carbon signals of 1 and 2 were observed in 3.94-4.15 ppm in the 13C-NMR spectra. These results strongly suggest that the cyclic carbonates are activated by TFA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2463-2471, 1998
    Additional Material: 5 Ill.
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  • 92
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    Rigid-rod liquid crystalline polyesters based on n-alkoxyterephthalic acid and 4,4′-dihydroxybiphenyl (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 263-267 
    Details
    ISSN: 0887-624X
    Keywords: rigid-rod ; liquid crystalline ; polymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and the characterization of a set of polymers obtained by polycondensation of n-alkoxyterephthalic acid (n = 1, 3, 5, 7) and 4,4′-dihydroxybiphenyl are reported. The n-alkoxy insertion promotes the processability of the material by lowering the melting temperature. All polymers show the nematic phase at about 300°C, almost independently of the length of lateral substituent. The isotropization is not observed up to 450°C, where thermal decomposition occurs. The temperature of glass transition decreases with increasing n, ranging from 170°C (n = 5) to 220°C (n = 1). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 263-267, 1998
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  • 93
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    Living radical polymerization of methylstyrenes by a stable nitroxyl radical, and stability of the aminoxy chain end (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 269-276 
    Details
    ISSN: 0887-624X
    Keywords: living radical polymerization ; methylstyrene ; MTEMPO ; stability ; aminoxy chain end ; steric hindrance ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical polymerization of 2-, 3-, and 4-methylstyrenes (MeSts) was investigated with benzoyl peroxide (BPO) as an initiator, in the presence of 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO). The polymerization was performed in bulk for 3.5 h at 95°C, and then continued for a defined time at 125°C, to give the corresponding poly(MeSt)s with narrow polydispersity in high yield. It was found that the polymerization proceeded in accordance with a living mechanism, because the molecular weight of the resulting polymers was proportional to the conversion, and to the reciprocal of the initial concentration of MTEMPO. It was found that steric hindrance between the methyl group of 2-MeSt, and the tetramethyl ones of MTEMPO, significantly contributed to the rate of polymerization, and to the stability of the growing polymer chain end. The stability decreased in the order of 2- 〉 3- 〉 4-MeSt, by occurrence of decomposition, which was caused by disproportionation of the growing chain end. However, the steric hindrance had no effect on the tacticity of the resulting polymer. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36, 269-276, 1998
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  • 94
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    Synthesis and characterization of poly(benzazoles) containing the bicyclo[2.2.2]octane moiety (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 277-281 
    Details
    ISSN: 0887-624X
    Keywords: poly(benzazoles) ; bicyclo[2.2.2]octane ; aromatization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(benzobisoxazoles) (PBOs), poly(benzobisthiazoles) (PBTs) and copolymers thereof containing the 2,5-dihydroxybicyclo[2.2.2]octane moiety have been prepared and studied. The homopolymers were synthesized by the polycondensation of 2,5-dihydroxybicyclo[2.2.2]octane-1,4-dicarboxylic acid with 4,6-diamino-1,3-benzenediol dihydrochloride or 2,5-diamino-1,4-benzenedithiol dihydrochloride in poly(phosphoric acid). Random and block copolymers (PBO-PBT) were also prepared. The polymers were characterized by solubility, X-ray diffraction, spectroscopy (infrared and solid-state 13C nuclear magnetic resonance), and thermal analysis such as differential scanning calorimetry and thermogravimetric analysis. Thermogravimetric analysis showed thermal stability of the polymers above 375°C in air and under argon atmosphere. The polymers exhibited high resistance to organic and inorganic solvents. The polymers were converted to the more stable aromatic polymers via dehydration and retro Diels-Alder reactions of the 2,5-dihydroxybicyclo[2.2.2]octyl moiety by pyrolysis. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 277-281, 1998
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  • 95
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    Photoinduced surface relief gratings in high-Tg main-chain azoaromatic polymer films (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 283-289 
    Details
    ISSN: 0887-624X
    Keywords: polyurea ; azoaromatic group ; surface relief grating ; holographic material ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have synthesized two classes of polyureas with mono- and bisazoaromatic groups in their main chains via reactions between isophorone diisocyanate and the corresponding diamines. Holographic gratings were fabricated on azoaromatic polyurea films prepared by spin-coating from solutions. The effect of high glass transition temperature and dipole moment of azo groups on the formation of gratings was investigated. Although the two polymers have relatively high glass transition temperatures (197 and 236°C), chromophore alignment was induced by laser beam irradiation at modest light intensities. Regularly spaced surface relief gratings on the polymer film were also recorded upon exposure to an interference pattern of two polarized argon laser beams. Erasure could be achieved by heating above Tg or by exposure to one of the beams in a manner similar to low-Tg side-chain azo polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 283-289, 1998
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    Synthesis and properties of nonlinear optical side chain soluble polyimides for photonics applications (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 301-307 
    Details
    ISSN: 0887-624X
    Keywords: polyimides ; electrooptics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aromatic polyimides with side chain nonlinear optical chromophores have been investigated through a facile two-step synthetic route. First, various poly(hydroxy imide)s have been synthesized by direct thermal imidization of diaminophenol dihydrochloride salt and aromatic dianhydride monomers. The resulting polyimides bearing phenolic hydroxy groups were found to react easily with the terminal hydroxy group on the chromophores via the Mitsunobu condensation to give corresponding polyimides with high optical nonlinearities and good solubility in common organic solvents. Detailed physical properties showed that these polyimides have a molecular weight (Mw) of 31,000 and high glass transition temperature above 220°C, ensuring a long-term alignment stability at elevated temperature. The electrooptic coefficients, r33, of the electrically poled polymer films were in the range 1.8-7.6 pm/V at 1.3 μm. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 301-307, 1998
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    Polymer grafting onto carbon black by use of TEMPO-terminated polystyrene with controlled molecular weight (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 3165-3172 
    Details
    ISSN: 0887-624X
    Keywords: carbon black ; surface grafting of polymer ; living radical polymerization ; TEMPO-terminated polystyrene ; radical trap ; dispersibility ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The grafting of polystyrene with controlled molecular weight and narrow molecular weight distribution onto the carbon black surface through the trapping of polymer radicals formed by the thermal dissociation of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-terminated polystyrene (PSt-TEMPO) by the carbon black surface was investigated. PSt-TEMPO was prepared by living radical polymerization of St with the benzoyl peroxide/TEMPO system. When PSt having no terminal TEMPO moiety was heated with carbon black, no grafting of PSt onto the surface was observed. On the contrary, by the heating of PSt-TEMPO with carbon black in m-xylene at 125°C, PSt with controlled molecular weight and narrow molecular weight distribution was grafted onto the surface: the percentage grafting of PSt (Mn = 3.2 × 103;Mw/Mn = 1.07) onto furnace black was determined to be 16.0%. On the basis of the above results, it is concluded that PSt radicals formed by the thermal dissociation of the C—ON bond between PSt and TEMPO are trapped by polycondensed aromatic rings of carbon black. The mole number of grafted PSt chains on the carbon black surface decreased with increasing molecular weight of PSt-TEMPO. PSt-grafted carbon black gave a stable colloidal dispersion in THF. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3165-3172, 1998
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    Ethene-propene copolymerization with the MgCl2-supported dichlorobis(4,4,4-trifluoro-1-phenyl- 1,3-butanedionato)titanium catalyst activated by an ordinary trialkylaluminum (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2735-2740 
    Details
    ISSN: 0887-624X
    Keywords: Ti(BFA)2Cl2/MgCl2 catalyst (BFA = 4,4,4-trifluoro-1-phenyl-1,3-butanedione) ; activation by trialkylaluminum with or without diisopropyldimethoxysilane ; copolymerization of ethene with propene ; homogeneity of active species ; homogeneity of copolymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Ti(BFA)2Cl2/MgCl2-Al(C2H5)3 catalyst (BFA = 4,4,4-trifluoro-1-phenyl-1,3-butanedione) modified by DIPDMS (diisopropyldimethoxysilane), which had been proved to yield an extremely high isotactic polypropene in high selectivity, was tested for the copolymerization of ethene with propene. The analysis of resulting copolymers by CFC (cross fractionation chromatography) indicated the formation of a small quantity of ethene-rich copolymers as a byproduct, suggesting that the catalyst possesses not only Ti(III) species but a small portion of Ti(II) species. Whereas, the same catalyst without being modified by an external donor selectively yielded propene-rich random copolymers resulting from Ti(III) species in high yields. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2735-2740, 1998
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    Styrene-assisted free radical grafting of glycidyl methacrylate onto polyethylene in the melt (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2763-2774 
    Details
    ISSN: 0887-624X
    Keywords: free radical grafting ; glycidyl methacrylate ; polyethylene ; styrene ; reactive extrusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Glycidyl methacrylate (GMA) is a very useful monomer as it bears an epoxy group which is capable of reacting with various other functional groups. However, its melt free radical grafting reactivity onto a polymer backbone is low. In this study, we show that the use of styrene (St) as a comonomer greatly promotes both GMA's grafting yield and grafting rate onto polyethylene (PE). It is proposed that, in the presence of St, the dominant mechanism of the free radical grafting of GMA onto PE is that St reacts first with PE secondary macroradicals and the resulting styryl macroradicals then copolymerize with GMA leading to grafted GMA. We also show that the contribution of St is not related to an improved solubility of GMA in the molten PE. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2763-2774, 1998
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  • 100
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    Highly branched radial block copolymers via dendritic initiation of aliphatic polyesters (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2793-2798 
    Details
    ISSN: 0887-624X
    Keywords: highly branched radial block copolymers ; dendritic initiation ; alipatic polyesters ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Living ring opening polymerization of ε-caprolactone initiated from the numerous chain-end hydroxymethyl groups of the analogous dendrimeric and hyperbranched polyesters derived from 2,2-bis(hydroxymethyl) propionic acid is described. By controlling the size of the dendritic macromolecule and the molar ratio of ε-caprolactone, a variety of highly branched radial block copolymers are obtained. Comparison of the results obtained for the dendrimeric and hyperbranched initiators demonstrates that the reactivity of the chain-end hydroxymethyl groups in the dendrimer are significantly greater than in the isomeric hyperbranched case. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2793-2798, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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