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  • Electronic Resource  (18)
  • 1985-1989  (18)
  • 1925-1929
  • 1880-1889
  • 1850-1859
  • Polymer and Materials Science  (18)
  • 1
    Electronic Resource
    Electronic Resource
    Multiple denaturational transitions in fibrillar collagen (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1875-1893 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The heat denaturation of pepsinized bovine nonfibrillar and fibrillar collagen was studied by differential scanning calorimetry. For fibrillar preparations that had been rapidly precipitated with stirring at low ionic strength, then resuspended at physiological ionic strength, multiple denaturational transitions were observed. At heating rates of 10°C/min, melting endotherms occurred at about 44, 50, 53, and 57°C. Fibrillar collagen that was slowly gelled without stirring at physiological ionic strength exhibited a similar series of endotherms, but the lower melting transitions were less conspicuous. In contrast, nonfibrillar bovine collagen in acidic solution showed only a single denaturational transition at 40°C. Nonfibrillar solutions at pH 7, to which inhibitors of fibrillogenesis were added, showed a major endotherm as high as 46°C. These results suggest that reconstituted fibrillar collagen contains a heterogeneous fibril population, possibly including molecules in a nonfibrillar state. It was proposed that the multiple melting endotherms of such preparations were due to sequential melting of molecular and fibril classes, each with a distinct melting temperature. The fibrillar classes may represent three or more types of banded and nonbanded species that differ from each other in packing order, collagen concentration, and possibly also in fibril width and level of cross-linking.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360251006
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of pH and temperature on cardioactive polypeptides from sea anemones: A 1H-nmr study (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1143-1157 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of pH and temperature on the 300-MHz 1H-nmr spectra of three cardioactive polypeptides from sea anemones, anthopleurin-A from Anthopleura xanthogrammica (AP-A) and Anemonia sulcata toxins I and II (ATX I and II), are described. AP-A and ATX II exhibit major spectral heterogeneity. Evidence from the pH and temperature studies and from high performance liquid chromatography indicates that this heterogeneity is conformational rather than chemical in origin. By contrast, purified isotoxins of ATX I show no evidence of conformational heterogeneity. The pKa values of most of the ionizable groups in these polypeptides are not strongly perturbed by interactions in the tertiary structure, with the exception of one of the Asp carboxylates, which has a pKa of ≲ 2 in AP-A and ATX II and 3.0 in ATX I. Protonation of this carboxylate, suggested to be Asp-9, leads to a conformational change in all three molecules. All three polypeptides are thermally stable, showing some conformational changes but not major unfolding at elevated temperatures.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270708
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  • 3
    Electronic Resource
    Electronic Resource
    Dielectric studies of the cure of epoxy matrix systems (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 1155-1167 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dielectric spectroscopy was used to monitor the curing process of two epoxy resin systems. The basic system (system I) consisted of DGEBA (a difunctional epoxy) and a polyamide in a 50-phr mixture. In addition, a comparative analysis was performed on a high-performance resin system (system II) used primarily in unidirectional composite applications. This system contained TGDDM (a tetrafunctional epoxy) and DDS (a tetrafunctional amine) in a 25-phr mixture. The dielectric data were obtained using a simple yet functional sample cell electrode designed and constructed in the laboratory. For system I, isothermal dielectric data were used to determine apparent activation energies for the temperature range from 22 to 70°C. The data showed that the activation energy was a function of temperature and increased as the temperature of the cure increased. This indicated that the reaction mechanism was also a function of temperature. For system II, data were collected between 140 and 190°C and an overall activation energy for that temperature range was determined. The overall activation energies for both systems, calculated using dielectric spectroscopy, compared favorably to those obtained using differential scanning calorimetry. Also, using a wider frequency range (240 Hz to 2 MHz), Argand diagrams were constructed and modeled with the Cole-Cole empirical equation for systems with a distribution of relaxation times. This justified the calculation of average relaxation times, which could then be related to the bulk physical properties of the polymer, such as viscosity. Modified Argand diagrams, where ε″ is plotted against ε′ at one frequency as a function of time, were also constructed, which aided in the understanding of the curing processes for these thermosetting systems.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070310501
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  • 4
    Electronic Resource
    Electronic Resource
    The modification of polysulfone by metalation (1988)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 26 (1988), S. 123-127 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1988.140260211
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  • 5
    Electronic Resource
    Electronic Resource
    Miniemulsion copolymerization of vinyl acetate and butyl acrylate. III. Experimental evidence for the role of the cosurfactant (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 193-202 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The role of the cosurfactant (hexadecane) in the miniemulsion copolymerization of 50 : 50 molar ratio vinyl acetate-butyl acrylate monomer mixture is analyzed from an experimental point of view. The main factor responsible for the different kinetic behavior between the miniemulsion and conventional emulsion copolymerization processes was found to be the different particle nucleation mechanism operating in each process. Experimental evidence is presented indicating that in the miniemulsion copolymerization particle nucleation takes place in the preformed stable submicron monomer droplets.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080270117
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  • 6
    Electronic Resource
    Electronic Resource
    Miniemulsion copolymerization of vinyl acetate and butyl acrylate. I. Differences between the miniemulsion copolymerization and the emulsion copolymerization processes (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 861-874 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differences between the emulsion copolymerization and miniemulsion copolymerization processes, in terms of emulsifier adsorption, emulsion stability, polymerization kinetics, copolymer composition and dynamic mechanical properties were studied for the comonomer mixture of 50:50 molar ratio vinyl acetate (VA+) - butyl acrylate (BuA), using sodium hexadecyl sulfate (SHS) as a surfactant and hexadecane (HD) as a co-surfactant. The use of hexadecane with the appropriate SHS initial concentration led to a higher adsorption of surfactant, smaller droplet size, higher stability of the emulsions, lower polymerization rates, and larger latex particle size. The copolymer composition during the initial 70% conversion was found to be less rich in Vac monomer units for the miniemulsion process. The dynamic mechanical properties of the copolymer films showed less mixing between the BuA-rich core and the VAc-rich shell in the miniemulsion latexes compared to the conventional latex films.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080240505
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  • 7
    Electronic Resource
    Electronic Resource
    Structure-property relationships of ionene polymers (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 87-109 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of new ionenes was accomplished by the reaction of novel diamines and dihalides. A new class of crosslinkable ionenes was made possible by the synthesis of tertiary diamines with acrylate functionality, generated ultimately from diepoxides and secondary amines. Other tertiary diamines were produced by endcapping of diols with tolylene diisocyanate, followed by reaction with N,N-dimethylethanolamine and also termination of living poly(tetrahydrofuran) polymer with dimethylamine. New dihalides were produced by the opening of diepoxides with ω-bromoacids.These diamines and dihalides underwent Menschutkin reactions providing novel ionenes for structure-property relationship studies. Correlations were drawn concerning amine nucleophilicity, dihalide nucleofugascity, and molecular weight. Stress-strain and thermal data reflected the effects of ionic domains and large flexible segments in the polymers. Also considered were the electrical conductivity, moisture-vapor transmission, and oxygen permeability of these materials.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080250109
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  • 8
    Electronic Resource
    Electronic Resource
    Materials, research - current issues and future directions (1989)
    Weinheim : Wiley-Blackwell
    Advanced Materials 1 (1989), S. 140-141 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19890010502
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  • 9
    Electronic Resource
    Electronic Resource
    An evaluation of ultrathin ring and band microelectrodes as amperometric sensors in electrochemical flow cells (1989)
    Weinheim : Wiley-Blackwell
    Electroanalysis 1 (1989), S. 23-33 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gold and platinum ultrathin ring microelectrodes (0.1-0.5 mm thick, 1.5-4 mm diameter) were made by sputtering, from fired metalloorganic paint, and from foil for use as sensors in a thick-layer wall-jet flow cell. An end-on array of three 0.1 μm × 0.5 mm gold band electrodes were mounted parallel to the flow direction in a thin-layer channel cell. These ultrathin sensors, along with a jet-centered carbon microdisk, were evaluated in the amperometric flow-injection mode for temporal stability, calibration sensitivity, detectivity, background signal, and flow rate dependence of the analytical signal using ferrocene samples in acetonitrile containing 10-4-10-2 M TEAP. The detectivity of gold paint ring electrodes made on borosilicate glass was 3-6 nM, an order of magnitude lower than any of the other electrodes tested. Analytical signals from gold paint and foil rings and the carbon microdisk had the best temporal stability. The current for the ultrathin band array in a channel cell was flow rate-independent, and the exponential dependence of cell current on flow rate was 0.11-0.14 for ultrathin rings in the thick-layer wall-jet mode.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140010105
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  • 10
    Electronic Resource
    Electronic Resource
    Small-angle x-ray scattering studies of thermally-induced morphological changes in segmented polyurethane elastomers (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 885-907 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of temperature on the morphology of a series of polyether and polyester polyurethanes has been studied using small-angle x-ray scattering. Scattering curves were obtained in situ at high temperature (90 and 150°C) and also later at room temperature to study the effects of thermal history on the materials. In general, annealing improves the degree of phase separation and increases the hard domain size in the materials studied. Annealing improves the degree of phase separation in more compatible systems to a greater degree than in less compatible systems. Increased interfacial mixing is apparent in the materials studied in situ at high temperatures. Thicker interfacial regions are also present in the annealed material relative to the control.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1986.090240414
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