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  • Polymer and Materials Science  (1,352)
  • 2020-2024
  • 2020-2022
  • 1985-1989  (1,162)
  • 1955-1959  (190)
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Keywords
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Isocyanate-terminated polybutadiene prepolymers: Synthesis, characterization, and end-group modifications (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 1433-1441 
    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: Telechelic prepolymers of butadiene with aliphatic isocyanate end-groups were prepared by the solution polymerization of butadiene under free radical initiation. 4,4′-Azobis (4-cyanopentanoyl azide) was used as the initiator. Liquid prepolymers were obtained with molecular weights of 1450 to 6000 and functionalities 1.9 to 2.2. The prepolymers were characterized by their number-average molecular weight, isocyanate content, functionality, infrared, and nuclear magnetic resonance spectra and microstructure. The storage stability of the prepolymers was checked and they were found to be quite stable under ambient conditions. Isocyanate-terminated polybutadienes were reacted with N,N-dimethylamino ethanol and t-butyl hydroperoxide to obtain useful dimethylamino-terminated and peroxycarbamate-terminated prepolymers, respectively.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070360613
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  • 2
    Electronic Resource
    Electronic Resource
    Drag reduction by polymer-polymer mixtures (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 837-858 
    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: An extensive study on the turbulent drag reduction caused by the various mixtures of polyacrylamide, purified guargum, xanthangum, and their graft copolymers has been conducted at low concentrations and Re = 14,000 using a turbulent flow rheometer. It has been found in most of the cases that the drag reduction caused by mixtures shows a positive deviation from the linearly additive straight line. This effect is more prominent when the drag reduction caused by both the constituents differ appreciably. In most of the cases, the drag reduction caused by the mixtures is higher than the DR caused by either of the constituent polymers; however, the drag reduction caused by the mixture is less than the sum of the drag reduction caused by both the constituents at their respective concentration in the mixture. It has also been noticed that there is no evidence of synergism in these mixtures at low concentrations.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070360409
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  • 3
    Electronic Resource
    Electronic Resource
    Decomposition rate studies of azobisnitriles containing functional groups (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 953-958 
    Details
    ISSN: 0887-624X
    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/pola.1988.080260321
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  • 4
    Electronic Resource
    Electronic Resource
    Cellulose-induced crosslinking of polyethylene (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 3057-3060 
    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
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070371020
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  • 5
    Electronic Resource
    Electronic Resource
    Tissue reaction to intraperitoneal polymer implants: Species difference and effects of corticoid and doxorubicin (1989)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 705-718 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The peritoneal cavity is a convenient site for implantation of encapsulated hormonesecreting tissue. However, host tissue organization around such implants may affect solute exchange and viability of the encapsulated tissue. The reaction to polyvinyl chloride acrylic copolymer capsules implanted in the peritoneal cavity of rats and mice was therefore studied. Some animals received a slow release dexamethasone pellet, others were pretreated with doxorubicin, in an attempt to minimize the tissue reaction. The tissue reaction was significantly thicker in rats than in mice at both 2 and 6 weeks after implantation. In rats, corticoids decreased significantly the thickness of the reactive layer as compared to control at all time points studied, but doxorubicin had no effect. The tissue reaction in mice was not significantly affected by corticoid treatment. In both species the thickness of the tissue reaction did not increase significantly between 2 and 6 weeks. At 3 days the tissue reaction consisted of an interrupted single layer of macrophages in mice, whereas in rats the reaction consisted of two or three layers of macrophages and polymorphonuclear cells. At both 2 and 6 weeks, several cell layers surrounded the implants: a single layer of macrophages lying along the polymer, a variable number of layers of fibroblasts interspresed with collagen fibrils (fewer in mice than in rats, and fewer in corticoid treated rats than control rats) and an outer monolayer of mesothelial cells. We conclude that the intensity of tissue reaction to polymer implants in the peritoneal cavity is species dependent and can be decreased by the administration of corticoids but not doxorubicin.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820230704
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  • 6
    Electronic Resource
    Electronic Resource
    Conformational effects on peptide aggregation in organic solvents: Spectroscopic studies of two chemotactic tripeptide analogs (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1131-1146 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aggregation behavior of the chemotactic peptide analogs, Formyl-Met-Leu-Phe-OMe (1) and Formyl-Met-Aib-Phe-OMe (2), has been studied in chloroform and dimethylsulfoxide over the concentration range of 0.2-110 mM by 1H-nmr spectroscopy. Both peptides associate in CDCl3 at concentrations ≥ 2 mM, while there is no evidence for aggregation in (CD3)2SO. Analog 1 adopts an extended conformation in both solvents favoring association to form β-sheet structures. A folded, γ-turn conformation involving a 3 → 1 hydrogen bond between Met CO and Phe NH is supported by 1H-, 13C-nmr, and ir studies of analog 2. The influence of backbone conformation on the ease of peptide aggregation is demonstrated by ir studies in CHCl3 and CD studies in dioxane.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240703
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  • 7
    Electronic Resource
    Electronic Resource
    Conformational analysis of cholecystokinin fragments CCK4, CCK5, and CCK6 by 1H-nmr spectroscopy and fluorescence-transfer measurements (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1663-1681 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The confortmational behavior of the cholecystokinin-related fragments CCK4, CCK5, and CCK6 as determined by 1H-nmr spectroscopy in DMSO-d6 and water and fluorescence-transfer measurements in aqueous medium are greatly dependent on the ionization states of these peptides. Under netral conditions, the backbones of CCK5 and CCK6 preferentially adopted folded forms with a β-turn including the four residues Gly-Trp-Met-Asp, probably stabilized by a hydrogen bond between the CO of Gly and the NH of Phe. In these structures, possible induced by an ionic interaction between the carboxylic group of Asp32 and the NH3+ group of the N-terminal amino acid, the lateral chains of the various residues are quite distant from each other (15-16 Å). Under acidic conditions, extended structures without interactions between side chains predominate for CCK5 and CCK6, while for CCK4, a conformational change drawing the Trp and Phe side chains in close proximity was shown by fluorescence. The conformations observed in aqueous medium at physiological pH are discussed in relation to the biological activity of these peptides.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240903
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  • 8
    Electronic Resource
    Electronic Resource
    Counterion diffusion in heparin solutions (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1179-1186 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The physiological importance of heparin is due to its strong interaction with bivalent counterions, especially Ca2+. A diffusional approach of this property is presented in this article: the observable is the self-diffusion coefficient of the counterions, as a function of the ratio of the polyelectrolyte over the added salt concentrations. All the results are in agreement with a simple “quasi-chemical model” in which two different states are assumed for the counterions: “free” or “bound.” The proportions of these two types of ions are calculated according to the distribution function of the counterions around the polyion. We assume that those of counterions located at a distance closer than a, the characteristic distance, are bound; the others are free. The ionic distribution function is evaluated by a numerical integration of a cell model Poisson-Boltzmann equation. Finally, this model leads to a very good agreement with the experimental results, if the radius of heparin polyion is assumed to be 6 and 10 Å.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280609
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  • 9
    Electronic Resource
    Electronic Resource
    Conformations and mitochondrial uncoupling activity of synthetic emerimicin fragments (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 683-701 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several amino terminal fragments of the emerimicins (Ac-Phe1-Aib2-Aib3-Aib4-Val5-Gly6-Leu7-Aib8-Aib9-Hyp10-Gln11-D-Iva12-Hyp13-Ala/Aib14-Phol15) ranging in length from five to ten residues have been synthesized. Nuclear magnetic resonance studies have been carried out on the 1-5, 6-10, 1-6, 1-7, 1-8, 1-9, and 1-10 fragments. The number of solvent-shielded NH groups in CDCl3 solutions for 1-5, 1-6, 1-7, 1-8, 1-9, and 1-10 indicate that 310-helical structures are favored in this solvent. In (CD3)2SO, an additional NH group, assigned to Aib(3) NH is solvent exposed in the fragments longer than six residues, suggesting partial unfolding of the N-terminal β-turn or transition to an α-helical conformation. The data for fragment 6-10 are consistent with a conformation having a single Leu-Aib β-turn. Infrared studies suggest an increase in the number of intramolecular hydrogen bonds with increasing peptide chain length. Appreciable mitochondrial uncoupling activity is observed for peptides with a chain length of at least seven residues. The order of efficiencies of the fragments is 1-7 〈 1-8 ∼ 1-10 〈 1-9, with the decapeptide exhibiting anomalously low uncoupling activity.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270411
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  • 10
    Electronic Resource
    Electronic Resource
    Correlation between the sequence-length distribution and structure of statistical copolymers of L-valine and γ-benzyl-L-glutamate (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 705-725 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Statistical copolymers were prepared from N-carboxyanhydrides of L-valine and γ-benzyl-L-glutamate in dioxan with triethylamine as an initiator. The copolymerization conversion was determined by ir spectroscopy, the copolymer composition by amino acid analysis, and the molecular weights by light scattering. The monomer reactivity ratios were found to be rVal = 0.14 and rGlu(OBzl) = 6.4. High-molecular-weight copolymers are formed even at low conversions. The content of β-structure in the copolymers was estimated from the ir spectra in copolymerization mixtures. The sequence-length distribution of L-valine and γ-benzyl-L-glutamate copolymers was calculated and its dependence on copolymerization conversion is discussed. Relations between the sequence-length distribution and the content of β-structure were studied. It was found that the content of β-structure in samples with the same composition is different for low- and high-conversion copolymers. The formation of β-structure in copolymers in the copolymerization mixture requires a certain minimal sequence length, which has been found to be about 6 valine units.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360260511
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