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  • 1
    Electronic Resource
    Electronic Resource
    Molecular characterization of branched thermoplastic polyurethane in dilute solutions on N-methyl-2-pyrrolidinone (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 241 (1996), S. 113-122 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Sieben polymerhomologe Proben eines thermoplastischen Polyurethans (TPU) wurden in verdünnter Lösung in N-Methyl-2-pyrrolidinon (NMP) mit Größenausschlußchromatographie (SEC) auf Normalphase-Silicagel, Viskosimetrie bei kleinem Schergefälle und Membranosmometrie charakterisiert. Die Staudinger-Mark-Houwink (SMH)-Konstanten dieser homologen Serie wurden mit einer neuen Methode auf der Basis der universellen Kalibrierung der SEC mit engen Polystyrol-Standards berechnet. Die ermittelten SMH-Konstanten dieser TPU-Proben in NMP bei 298 K (K = 3,94 mL g-1, a = 0,29) bewiesen die verzweigte Struktur dieser TPU-Proben und wurden durch die Osmometrie bestätigt.
    Notes: Seven homologous samples of a thermoplastic polyurethane (TPU) were characterized in dilute solutions of N-methyl-2-pyrrolidinone (NMP) by size exclusion chromatography (SEC) on normal-phase silica gel, low-shear viscometry and membrane osmometry. The Staudinger-Mark-Houwink (SMH) constants of this homologous series were obtained by a new procedure of calculation on the basis of universal calibration of SEC with narrow polystyrene standards. The calculated SMH constants for these TPU samples in NMP at 298 K (K = 3.94 mL g-1, a = 0.29) prove the branched structure of this TPU samples and were further confirmed by osmometry.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052410109
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of miller indices of side faces of small crystallites from scanning force microscopy angle measurementsDedicated to Professor K. Dransfeld on the occasion of his emeritation. (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 409-415 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The calculation of Miller indices from out-of-plane angle measurements with scanning force microscopy (SFM) is demonstrated on three different systems: rutile on haematite, rutile on sapphire and haematite on sapphire. The height of the investigated crystallites ranges from several millimetres (rutile on haematite) down to 〈10 nm (haematite on sapphire). General issues of goniometry by means of SFM, such as the influence of the scanner calibration, the adjustment of the feedback loop on the error involved in out-of-plane angle measurements and the limitation of SFM goniometry due to tip geometry, are discussed and a comparison with other methods are given.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740230613
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  • 3
    Electronic Resource
    Electronic Resource
    Some special aspects of thermal ageing of isotactic polypropylene (measuring method: Isothermal long-term DTA)Vortrag anläßlich des 18. Donauländergesprächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24.-26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 321-334 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: An Folien (Dicke 100 pm) aus isotaktischem Polypropylen mit verschiedenen Antioxidansgehalten (0,0% bis 0,1%) wird die thermooxidative Alterunq mit der isothermen Langzeit-Differential-Thermo-Analyse (ILDTA) bis zu Temperaturen weit unter dem Kristallitschmelzbereich verfolqt und die Messwerte mit Ergebnissen aus dem Zeitstand-Zugversuch korreliert. Dabei zeigt sich, daß aus Messunqen mit der ILDTA bereits vor Einsetzen der autokatalytischen Zersetzunq sreaktion Ruckschlüsse auf die thermische Vorqeschichte der Proben und Aussagen auf das rnit einem Abfall der mechanischen Eigenschaften verbundene Ende der thermo-oxidativen Stabilität des Polymeren getroffen werden können.Weiters bietet die ILDTA die Moglichkeit, durch den direkten Zusamenhang zwischen Oxidationszeit und Antioxidansögehalt die örtliche Stabilisatorverteilung in Platten und in Folien zu bestimmen und damit Diffusionsvorqange zu verfolgen.
    Notes: Thermo-oxidative ageing processes were investigated in films (100 μm thick) made from isotactic polypropylene with different antioxidant concentrations between 0% and 0.1% using isothermal long-term differential thermal analysis (ILDTA). The end of the oven life of polypropylene coincided with the loss of mechanical properties which was confirmed by tensile tests at temperatures far below the crystallite melting range. Already prior to the beginning of autocatalytic decomposition, ILDTA experiments permits conclusions to be drawn on the thermal history of the specimens and statements made regarding the end of thermo-oxidative stability of the polymer, which is accompanied by a deterioration in the mechanical properties.In consequence of the correlation between oxidation time and antioxidant concentration the local antioxidant concentration in sheets or films can be measured by ILDTA. Thus, investigating the diffusion of an antioxidant in polypropylene using ILDTA is possible.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051580119
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  • 4
    Electronic Resource
    Electronic Resource
    Cationic surface modification by polyelectrolytes: Polyelectrolyte complex formation at inorganic particle surfaces (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 207 (1993), S. 203-213 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die negativ geladene Oberfläche von feindispersen anorganischen Materialien wie Kieselgur, Perlit, Kaolin oder Glas kann durch die Adsorption von kationischen Polyelektrolyten umgeladen werden. Bei hohen Mengen an adsorbiertem Polykation besitzen die Oberflächen der unterschiedlichen Materialien dann gleiche elektrokinetische Eigenschaften. An den derart modifizierten Grenzflächen können anionische Farbstoffe adsorbiert werden. Bei Zugabe eines Polyanions, resultierend in der Bildung eines Polyelektrolytkomplexes, kann die Zahl der kationischen Zentren in der Grenzfläche und damit die Adsorptionskapazität für den Farbstoff erhöht werden. Die experimentellen Resultate deuten darauf hin, daß das Zetapotential bestimmt wird durch die außeren Bereiche der PEC-Schicht, wahrend die Farbstoffadsorption auch durch die inneren Regionen der Oberfläche mitbestimmt wird. Unmittelbar nach der Modifizierung mit Poly(diallyldimethylammoniumchlorid) und Poly(maeinsäure-co-α-methylstyrol) besitzen die modifizierten Materialien bei einem hohen Überschuß des Poly-anions ein negatives Zetapotential, aber ein positives nach der Abtrennung der überstehenden Lösung. Dieses Verhalten steht in Übereinstimmung mit der Bildung eines nichtstochiometrischen PEC mit Polykation im Überschuß und einer reversiblen Wechselwirkung mit überschüssigem Polyanion in der Lüsung. Die Ergebnisse deuten an, daß die Oberflache als fest-analoger Polyelektrolyt in Konkurrenz zu dem Polyanion an der Reaktion beteiligt ist.
    Notes: The surface charge of inorganic finely dispersed materials like diatom earth, perlite, glass or clay may be changed from negative to positive by the adsorption of cationic polyelectrolytes. Different materials exhibit equivalent electrokinetic surface properties with high amounts of the polycation adsorbed. Interfaces modified this way are able to adsorb anionic dye stuffs. Their adsorption capability for the dye stuff may be enhanced by addition of polyanions due to the formation of a nonstoichiometric polyelectrolyte complex (PEC) and therefore an increased number of cationic centres in the interface. Experimental results indicate that the zeta potential is correlated to the outer PEC layer whereby dye stuff adsorption measurements are sensitive for the more inner surface regions, too. Immediately after modification, materials modified with poly(diallyldimethylammonium chloride) and poly(maleic acid-co-α-methylstyrene) have negative zeta potentials at high excess of added polyanion and a positive one after separation of the solid. This behaviour is attributed to the formation of a nonstoichiometric PEC with polycation in excess and reversible interaction with polyanion in the surrounding solution. Experimental results indicate that the surface may act as “solid-like” polyelectrolyte in competition to the polyanion.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1993.052070119
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  • 5
    Electronic Resource
    Electronic Resource
    Orientierung von Bacteriorhodopsin in einer Polymermatrix (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 185-198 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Bacteriorhodopsin is a component of the purple membrane of Halobacterium halobium. It shows photochemical activity and undergoes a series of photocyclic-associated conformational changes. Incorporated in a matrix it is suitable as a light energy/electrical current transducer. Very important is an orientation of purple membrane fragments.The reaction between solutions of a polyelectrolyte and multivalent ions leads to a ionotropic gel, that is a gel with an ordered structure. If the gel formation was carried out in the presence of purple membrane fragments, the Bacteriorhodopsin is highly oriented and produces a photoelectrical signal. It consists a correlation between the light direction and the orientation of the purple membrane due to the gel formation.
    Notes: Bacteriorhodopsin ist Bestandteil der sogenannten Purpurmembran des Mikroorganismus Halobacterium halobium. Es zeigt photochemische Aktivität und kann als biologischer Lichtwandler fungieren. Voraussetzung hierfür ist eine orientierte Anordnung der Purpurmembran in einer Matrix.Das Prinzip der ionotropen Gelbildung, d. h. die geordnete Strukturbildung einer Polyelektrolytlösung infolge eines gerichteten Diffusionsstromes von mehrwertigen Ionen gestattet die orientierte Anordnung der Purpurmembran. Durch Lichteinwirkung werden elektrische Signale induziert. Es besteht ein Zusammenhang zwischen der Richtung des Strahlungseinfalls und der durch die Gelwachstumsrichtung festgelegten Orientierung der Purpurmembran.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052290113
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetic properties and the electric field effect of life helix-coil transition of poly(γ-benzyl L-glutamate) determined from dielectric relaxation measurements (1968)
    New York : Wiley-Blackwell
    Biopolymers 6 (1968), S. 1263-1277 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dielectric relaxation of poly(γ-benzyl L-glutamate) in solution has been studied in the 5 kcps-10 Mcps range for various values of the helix content. The results give first experimental evidence for three effects of major significance. (1) The system exhibits dielectric relaxation due to a chemical rate process (namely helix formation). This confirms recent theoretical predictions. (2) The mean relaxation time τ* of the helix-coil transition could be evaluated as a function of the degree of transition. The results are in excellent agreement with a previously developed theory. At the midpoint of transition it is found τ*max = 5 × 10-7 sec. The elementary process of helical growth turns out to be practically diffusion-controlled (with a rate constant of hydrogen bond formation of 1.3 × 1010 sec-1). (3) There is a considerable electric field effect of the helix-coil transition. This indicates that conformation changes in biological systems could be potentially caused by direct action of an electric field.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1968.360060904
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  • 7
    Electronic Resource
    Electronic Resource
    Pervaporation and membrane distillation through membranes made of poly(2,6-dimethyl-1,4-phenylene oxide) (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 206 (1993), S. 193-198 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Eignung von Membranen aus Poly(2,6-dimethyl-1,4-phenylenoxid) für die Trennung von Wasser-Ethanol-Gemischen mittels Pervaporation wurde untersucht. Asymmetrische Membranen entstanden durch Phaseninversion, wobei Chloroform als Lösungsmittel und 1-Butanol als Nichtlöser zur Anwendung kamen. Homogene, dichte Membranen wurden aus Lösungen des Polymeren in Chloroform durch Abdunstung des Lösungsmittels erhalten. Nichtporöse Membranen, die bevorzugt permeabel für Wasser sind, entstanden entweder durch Abdunstung oder durch Fällung aus Lösungen mit geringem Nichtlöseranteil. Mikroporöse, aus Lösungen mit hohem Nichtlöseranteil hergestellte Membranen lassen bevorzugt Ethanol permeieren, vorausgesetzt, daß die Feedlösung die Membran nicht benetzt.
    Notes: The ability of poly(2,6-dimethyl-1,4-phenylene oxide) membranes to separate water-ethanol mixtures by pervaporation was examined. Asymmetric membranes were prepared from solutions containing chloroform as a solvent and 1-butanol as a nonsolvent by the phase-inversion process. Homogeneous, dense membranes were prepared from chloroform solutions by evaporation. Nonporous membranes (membranes precipitated from solutions with a low amount of the nonsolvent or prepared by evaporation) were preferentially permeable to water. Microporous membranes (precipitated from solutions with a high amount of the nonsolvent) were preferentially permeable to ethanol, provided the membrane is not wetted by the feed solution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1993.052060116
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  • 8
    Electronic Resource
    Electronic Resource
    On the displacement of cooperative transitions of linear biopolymers by an electric field (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1173-1179 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A basic theory for equilibrium properties of cooperative transitions (particularly helix-coil transformations) of sufficiently long linear biopolymers under the influence of an electric field is developed. General relations for the calculation of the distribution of uninterrupted sequences of elementary subunit states (e.g., helical fragments) as well as the overall degree of transition θ are given. Strong cooperativity is found to permit simplifications. It is shown that only in this case can a practically significant field effect be expected. Numerical results are presented for a special example of experimental interest.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140606
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  • 9
    Electronic Resource
    Electronic Resource
    The effects of cooperativity, finite chain length, and field-induced changes of the conformational equilibrium on the electric birefringence of polypeptides in the range of the helix-coil transition (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1181-1195 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An electric birefringence apparatus with an He-Ne laser is described, which permits a high sensitivity of measurement for field strengths up to 20 kV/cm and pulse durations between 10-5 to 1 sec. It is applied to poly(γ-benzyl-L-glutamate) and poly(β-benzyl-L-aspartate) in a nonaqueous solvent mixture, especially under the conditions of the helix-coil equilibrium. A theoretical treatment of the problem shows that the usual neglect of end effects is only justified for comparatively long chains. On the basis of a computational procedure taking into account the finite chain lengths, the experimental data for 15 kV/cm reveal an obvious enhancement of the coil-to-helix transition caused by the electric field. This effect is quantitatively confirmed by a pertinent theory. The cooperative parameter σ may be best determined from the initial linear increase of the bire-fringence versus the square of the field strength where the conformational equilibrium is not affected.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140607
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  • 10
    Electronic Resource
    Electronic Resource
    Über die polymerisation von 1,3-dithiolan-2,4-dionenHerrn Prof. Dr. H. Hellmann zum 60. Geburtstag gewidmet. (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 173 (1973), S. 43-65 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: 1,3-Dithiolane-2,4-diones (5) are distillable monomers, which are readily accessible from 2-halogeno carboxylic acids. Basic catalysts can effect a rapid polymerization to yield polyesters of 2-mercapto carboxylic acids, poly(thioalkylencarbonyl)s, (9) whereby rel. mol. masses up to 80000 may result. The catalytic effect of aprotic bases increases with increasing basicity because the initiation consists of a C—H-deprotonation of the monomer, whereas protic nucleophiles like primary amines, thiols or alcohols cannot catalyze the polymerization. The thermal decomposition of the monomers may also yield polyesters which form 1,4-dithian-2,5-dione (10) with increasing temperature. This degradation to 10 takes place at the chain ends. A rapid degradation of the polyesters is also effected by strong bases like trialkylamines or alcoholates even at room temperature and under anhydrous conditions.
    Notes: 1,3-Dithiolan-2,4-dione (5) sind destillierbare Monomere, die aus 2-Halogencarbonsäuren leicht zugänglich sind. Basische Katalysatoren können eine rasche Polymerisation zu Polyestern der 2-Mercaptocarbonsäuren, Poly(thioalkylencarbonyle), (9) bewirken, wobei sich rel. mol. Massen um 80000 erreichen lassen. Während primäre Amine und andere protische Nucleophile als Initiatoren wirkungslos sind, steigt die katalytische Aktivität aprotischer Basen mit zunehmender Basizität, da die wirkungsvollste Startreaktion aus einer C—H-Deprotonierung am Monomeren resultiert. Die thermische Decarboxylierung führt ebenfalls zur Polymerisation, doch wird mit steigender Temperatur in zunehmendem Maße 1,4-Dithian-2,5-dion (10) gebildet. Der thermische Abbau der Polyester zu 10 erfolgt bevorzugt am Kettenende. Ein rascher Abbau der Polyester wird aber auch schon bei Raumtemperatur und selbst unter wasserfreien Bedingungen von starken Basen, wie z. B. tertiären Aminen und Alkoholaten, bewirkt.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021730103
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