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  • Polymer and Materials Science  (477)
  • Wiley-Blackwell  (477)
  • Elsevier
  • 2000-2004
  • 1980-1984  (477)
  • 1940-1944
  • 2001
  • 1982  (239)
  • 1980  (238)
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 381-398 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Numerous hypotheses exist to explain observed blood-materials interactions. It is the purpose of this article to test two popular hypotheses, namely, the minimum interfacial free energy hypothesis and the optimum polar/apolar ratio hypothesis. Methacrylate polymers and copolymers were characterized using the captive bubble underwater contact angle method; bulk water content was determined by gravimetric methods; streaming potential measurements were made; and surface roughness and possible particulate contamination were evaluated by reflected light microscopy. In vitro blood tests include whole blood clotting time measurements on polymer-coated tubes; centrifugal force platelet adhesion on polymer-coated coverslips; and a measure of the partial thromboplastin time, Russell's viper venom time (Stypven time), and the prothrombin time of native whole blood exposed to polymer-coated microscope slides. Results suggest that platelet adhesion correlates in the opposite direction of whole blood clotting time and partial thromboplastin time, emphasizing the need for a multiparameter approach to blood-materials testing. Based on these tests the minimum interfacial free energy hypothesis is not supported. In fact, the data suggest the opposite to be true. It is apparent that platelet adhesion can be a misleading indicator of blood compatibility. Neither hypotheses can explain the apparent conflict between the platelet adhesion data and the coagulation time data.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 2 (1980), S. 5-10 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Mean free paths for inelastic scattering (λ) of low energy electrons in poly(methylmethacrylate) (PMMA) have been determined by measuring Al Kα excited C 1s and Si 2s photoelectron signal intensities as a function of ellipsometrically determined thicknesses of PMMA overlayers on silicon substrates. The λ values obtained are 29 ± 4 Å for 1196 eV electrons and 33 ± 5 Å for 1328 eV electrons. These data are necessary for the quantitative analysis of the surface region of PMMA and similar polymers by X-ray photoelectron spectroscopy (XPS). The magnitude of the λ values determined indicates that XPS measurements can provide chemical information about the surface region of polymers, such as PMMA, in the depth range of ∼6 to 100 Å. The results of this study are compared and discussed with respect to λ values determined for other organic compounds.
    Additional Material: 7 Ill.
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  • 3
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the poor solvent acetone/ethanol the viscosity of a 3% solution of 12.6% N pyro nitrocellulose is found to be related to the geometric mean of the number average and weight average molecular weights. The fractional increase in the viscosity of such a solution on the addition of lead ß-resorcylate is a function only of number average molecular weight. Once calibration has been made against osmotic pressure measurements and intrinsic viscosity, both number and weight average may be measured rapidly with an accuracy which is no less than that of the osmotic pressure and intrinsic viscosity measurements themselves.
    Additional Material: 3 Ill.
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  • 4
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of poly(ε-L-lysine) is described. This is a poly(ε-amino acid) in which the ε-amino group of lysine is condensed with the α-carboxyl group to produce a chain backbone that is a variant of the usual one seen in proteins and the side chain is the α-amino group. Conformational studies of poly(ε-L-lysine) and its t-butyloxycarbonyl derivative suggest the likelihood of a chain order that is formally similar to the antiparallel pleated-sheet conformation of proteins.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2265-2277 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Human fibrinogen was treated with thrombin in the presence of fibrinoligase (Factor XIIIa) and calcium ion at pH 8.5, ionic strength 0.45, and the ensuing polymerization was interrupted at various time intervals (t) both before and after the clotting time (tc) by solubilization with a solution of sodium dodecylsulfate and urea. Aliquots of the solubilized protein were subjected to gel electrophoresis on polyacrylamide gels after disulfide reduction by dithiothreitol and on agarose gels without reduction. The degree of γ-γ ligation was determined from the former and the size distribution of ligated oligomers, for degree of polymerization x from 1 to 10, from the latter. In some experiments, thrombin was inhibited, after partial polymerization, by p-nitrophenyl-p′-guanidinobenzoate. From these, it was concluded that for thrombin concentration ≤0.013 units/mL and fibrinoligase ≥30 mg/L, oligomer assembly is rapid compared with peptide A release and ligation is rapid compared with assembly. Under these conditions, the theory of the first paper of this series describes rather well the time dependences of the degree of γ-γ ligation, the weight fractions of monomer and small oligomers, and the number- and weight-average degrees of polymerization after solubilization of the staggered overlapped assemblies, each of which splits to give two strands of end-to-end ligated oligomers. The theory assumes that the second A peptide is released by thrombin more rapidly than the first by a factor q, which, from the experimental data, is determined to be 16. The subsequent assembly into staggered overlapped oligomers follows the statistics of linear polycondesation taking into account the presence of both difunctional and monofunctional combining units. For higher thrombin or lower fibrinoligase concentrations, ligation fails to keep pace with oligomer assembly, and the size distributions after solubilization show a higher proportion of very small and a lower proportion of larger ligated oligomers, owing to separation of the staggered overlapped assemblies into smaller fragments.
    Additional Material: 10 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 181 (1980), S. 1841-1846 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photo-oxidation of solid polymers at ambient temperatures is shown to be greatly affected by the low mobility of radicals in the solid state. When a radical pair, produced by photo-initiation, escapes the initial polymer cage, the probability of its recombination remains high even after several propagation steps. This phenomenon, known as secondary cage recombination, has a pronounced effect on the kinetics of oxidation and on the mechanism of photostabilisation by radical scavengers. The occurrence of secondary cage recombination is demonstrated for polypropylene photo-oxidation and a kinetic analysis is developed to predict the consequences of this effect.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 25 (1980), S. 575-588 
    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: As part of a continuing study of nonisothermal rheology (meaning the simultaneous application of strain and temperature changes), we here consider the behavior of polystyrene near the glass transition temperature Tg. In particular, we measured the increase of the apparent Tg as the cooling rate is increased from 0.003 to 4.5°C/sec. This change (up to 16°C increase) has both practical and theoretical implications. For enhancing the mechanical properties of a glassy product, one desires maximum orientation (stress) just prior to quenching; the optimum deformation/temperature strategy for maximizing stress is affected by the level of Tg. By using a nonisothermal strategy we were able to produce higher frozen-in orientations, and thus higher mechanical properties, than have been previously reported. For a theoretical understanding of the rubbery state just prior to quenching, we used the generalized time-temperature superposition of our prior work; we found that a modified shift factor of the form aT(T,TRg), where TRg refers to a rate-dependent Tg, gives an improved fit to data but is not by itself adequate.
    Additional Material: 14 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 3591-3595 
    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: Oligomers are potentially useful as well characterized models for studying the chemical and physical properties of their long chain homologues. These model compounds are often available only as mixtures which must be separated. This separation may be accomplished using chromatographic techniques, i.e., GPC. Polydispersity (Mw/Mn) is often used as a criteria for the extent to which separation has been achieved. Values of polydispersity of 1.01-1.03 are considered indicative of very narrow fractions in the high polymer area. A purpose of this paper is to show that such low values of polydispersity are misleading when applied to oligomers containing 2-20 repeat units. Further, the existence of a single “sharp” melting endotherm is not necessarily proof that one has separated out a single molecular weight component. An intimate mixture of different molecular weight oligomers can give a single narrow endotherm.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 33 (1982), S. 155-163 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Triphenylmethanfarben als Korrosionsinhibitoren für Aluminium-Kupfer-Legierungen in SalzsäureDie Inhibierung der Korrosion von Aluminium B 26 S in Salzsäure durch Triphenylmethan-, Anthrachinon- und Acridinfarben wurde unter Berücksichtigung von Säurekonzentration, Inhibitordosierung, Versuchsdauer und Temperatur untersucht. Im allgemeinen nimmt bei konstanter Säurekonzentration der Hemmwert von Malachitgrün, Methylviolett 6 B and „light green“ mit der Inhibitorkonzentration zu, während der von Fuchsinbase und Kristallviolett mit zunchmender lnhibitorkonzcntration geringer wird. Bei konstanter Inhibitorkonzentration nimmt andererseits die Wirksamkeit aller untersuchten Verbindungen (mit Ausnahme von Methylviolett 6 B und Acridinorange) mit steigender Säurekonzentration zu. Der Hemmwert aller untersuchten Verbindungen steigt im Temperaturbereich 20-50°C mit der Temperatur, während kein Einfluß der Versuchsdauer zu erkennen ist. Bei einer lnhibitorkonzentration von 0,1% in 0,5 M Salzsäure nimmt der Hemmwert in der folgenden Reihe zu: Fuchsinsäure (32%) 〈 Acridinorange 〈 Fuchsinbase (39%) 〈 Alizarinrot S (46%) 〈 Methylviolett 6 B (50%) 〈 Malachitgrun (64%) 〈 Kristallviolett (70%) 〈 „light green“ (80%).Die Wirkung der Inhibitoren scheint durch Absorption nach einer Langmuir-Adsorptionsisotherme bedingt zu sein. Das wird durch die Korrosionspotentiale bestätigt; allerdings dürfte bei galvanostatischer Polarisation die Kathode bevorzugt polarisiert werden.
    Notes: The inhibition of the corrosion of B 26 S aluminium in HCl solutions by triphenylmethane, anthraquinoid and acridine dyes has been studied in relation to the concentration of acid and inhibitor, duration of immersion and temperature. In general, at constant acid concentration, the inhibiting efficiency of malachite green, methyl violet 6 B and light green increases, whereas that of fuchsine base and crystal violet decreases as the inhibitor concentration increases. At constant inhibitor concentration the efficiency of all the compounds except methyl violet 6 B and acridine orange increases with increasing acid concentration. The inhibitive efficiency of all the compounds increases with temperature in the range 20-50°C, but no dependence can be recognized on the duration of immersion. At an inhibitor concentration of 0.1% in 0.5 M HCl the efficiency increases in the order: fuchsine acid (32%) 〈 acridine orange ≤ fuchsine base (39%) 〈 alizarin red S (46%) 〈 methyl violet 6 B (50%) 〈 malachite green (64%) 〈 crystal violet (70%) 〈 light green (80%).The inhibitors appear to function through adsorption following the Langmuir adsorption isotherm. From the corrosion potentials the inhibitors appear to function through general adsorption but under galvanostatic polarisation conditions, the cathode appears to be preferentially polarised.
    Additional Material: 9 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 741-750 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recently developed 13C-1H nuclear magnetic double-resonance techniques have been used to study proteins in the intact fetal enamel matrix. Enamel protein chains undergoing rapid, almost isotropic motion were detected in scalar decoupled 13C-nmr spectra, while motionally restricted enamel protein chains were principally observed in proton-enhanced spectra. The latter spectra were obtained using a matched Hartmann-Hahn contact to transfer polarization from protons to carbons (cross-polarization). Both mobile and motionally restricted enamel protein chains were observed in dipolar decoupled 13C-nmr spectra. A comparison of integrated intensities obtained from the scalar decoupled and dipolar decoupled spectra showed that 70% of the fetal enamel protein chains exhibit rapid, nearly isotropic molecular motion (τ ≲ 10-6 sec), while the remaining 30% are rigid or undergo only anisotropic molecular motion.
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