摘要:

AbstractThe fundamental vibrational frequencies of an isolated chain ofcis‐1,4‐polybutadiene have been calculated. Infrared and polarized Raman data are used in the force constant refinement routine. The assignments of the vibrational frequencies are discussed in terms of the potential energy distribut

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120301

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractTaking into consideration results of our microscopy studies and data given in the literature on the structure of hedrites, ovoids, and spiral ovoids, we have developed optical models for these morphological entities. These models are applied to calculations of small‐angle scattered light intensity distributions for these structural elements. Analytic formulae computed for theVvandHvscattering patterns contain terms dependent only on azimuthal angle μ and vertical angle θ. For hedrites and ovoids, equations are derived relating the characteristic points of scattered light intensity patterns to structural parameters. The corresponding diagrams of light intensity distributions are gi

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120302

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractProcedures for obtaining hedrites, ovoids, and spiral ovoids in polyoxymethylene are described. Results of morphological studies on these structures by optical and electron microscopy are presented. Small‐angle light scattering studies on single isolated supermolecular structures are described. TheVvandHvdiffraction patterns obtained experimentally are discussed in the light of theoretical results of Part I of this stud

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120303

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe equilibrium and kinetics of gas sorption by a silicone rubber filled with highly adsorptive molecular sieves was studied. Sorption in this system is by two mechanisms: gas is simply dissolved in the polymer matrix according to Henry's law, while it is adsorbed by the dispersed sieve phase in accordance with a Langmuir's isotherm. The latter effectively immobilizes the gas molecules preventing their further diffusion. All equilibrium parameters were determined experimentally. Immobilization greatly affects sorption kinetics and renders conventional analyses invalid. A theory to account for this process was adapted from a previous analysis by Vieth and Sladek which assumes that the kinetics of adsorption is very fast compared to diffusion. For this situation the kinetics always assume a Fickean form. The experimental data agreed very well with the predictions of this theory in a comparison where all parameters were defined by independent experiments. It was found that a single effective diffusion coefficient describes sorption kinetics, steady‐state permeation, and time‐lag results once the effects of immobilization are properly accounted

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120304

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractHeterogeneous network polymers composed of rigid polypeptide chains and flexible polyether chains were synthesized. That is, poly(L‐glutamic acid) (PLGA) was crosslinked with poly(oxyethylene glycol) (PEG) at various carboxy/hydroxyl mole ratiosK. The solubility tests and hydrolysis of heterogeneous network polymers suggest that the crosslinking reaction proceeds by esterification. The dynamic mechanical properties of these polymers(100 Hz, −100–200°C) are greatly influenced by the presence of a trace of water and the weight per cent of PLGA. In addition, some of these polymers show only one maximum in the temperature dispersion of dynamic loss modulusE″ and tan δ, although their shape is rather broad. The x‐ray photographs of these polymers show an amorphous halo or weak Debye‐Sherrer rings. These findings suggest that these polymers are not simple adducts; neverthless PLGA and/or PEG

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120305

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe crystal structure of polyisobutylene was determined by x‐ray analysis. The orthorhombic cell, witha= 6.88 Å,b= 11.91 Å,c(fiber axis) = 18.60 Å (space group:P212121−D 24), contains two molecular chains each consisting of eight monomeric units in the fiber identity period. The chain conformation is essentially an (8/3) helix, but deviates appreciably from the exact (8/3) helix symmetry. The symmetry of the molecular chain is only a twofold screw axis in exact sense, and a crystallographic asymmetric unit consists of four monomeric units. The torsional angles arewhere M denotes the methyl group. The averaged skeletal CCH2C and CCM2C bond angles are 128° and 110°, respectively. The large CCH2C bond angles may be due to steric respulsion between the adjacent methyl groups, giving intramolecular distan

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120306

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe angle‐dependent, isotropic light scattering exhibited by a diluent‐swollen, ideal network is theoretically derived and compared with the light scattering exhibited experimentally by swollen real networks. In good diluents the difference is a measure of the spatial nonrandomness of the degree of crosslinking. A nonrandomness index (NRI) is introduced in terms of the Rayleigh ratios at zero scattering angle. A procedure is given for reliably obtaining the zero‐angle Rayleigh ratio from experimental data at finite angles (2–30°). Measurements are reported for a series of poly(2‐hydroxyethyl methacrylate) (PHEMA) networks, prepared at varying stages of dilution (in ethylene glycol, EG) and varying amounts of crosslinker (ethylene glycol dimethyacrylate, EGDMA). The theoretical Rayleigh ratios are calculated by employing the equilibrium degrees of swelling, refractive indices, and Young's moduli of the gels, measured in EG. The NRI is found to decrease upon decreasing the dilution during network formation and upon increasing the average crosslinking density. The NRI provides a probe of the network structure on a (sub)microscopic level. It is suggested that the NRI is closely correlated with the performance of elastomers under mechanical loading

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120307

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractSmall‐angle light scattering (SALS) in the solid state and x‐ray diffraction were used to investigate the development of anisotropic structure in water‐cast amylose films prepared under various conditions. The conditions investigated were different temperatures and relative humidities maintained during the drying of the films and different aging times and temperatures of the amylose solution prior to the casting of films. As revealed by SALS, the predominant morphology developing in these films was based on rod‐like scattering units of considerable size. At times, a low degree of spherulitic character was also evident in the films. All four experimental conditions affected the development of anisotropic structure, with the aging time and temperature producing the most noticeable effects. Increasing aging time and/or decreasing aging temperature markedly increased the rod‐like morphology of the films. On the other hand, crystallite sizes as measured by x‐ray diffraction remained constant at 24–28 Å, indicating no influence on the part of experimental conditions. These findings are discussed in the light of starch

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120308

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe rules formulated by Koningsveld for the determination of the critical concentration are shown to be in accord with the Flory‐Huggins theory. Sometimes, however, they may not refer to stable conditions, and their application in such cases will result in misleading conclusion

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120309

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractFour samples containing 40, 60, 80, and 97 wt‐% of poly(vinyl chloride), the rest being plasticizer and stabilizer, were tested by using the Weissenberg Rheogoniometer in the steady‐shearing mode at temperatures between 155 and 235°C and rates of shear\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma = 0.01 - 400 $\end{document}sec−1. The viscosity η versus\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}follows Graessley's theoretical dependence for infinitely entangled system. The primary normal‐stress difference coefficient ψ versus\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}is well described by the same theoretical function, used with the square of its argument. The temperature dependence of η0and ψ0shows discontinuities atT=Tb. The numerical values ofTbcan be calculated from the theory of the melting point depression due to diluent. The activation energy of viscous flowEηbelowTbis 5–9 times as large as above this temperature. The activation energy of normal stress is found to beEψ ≈ 5Eη. The characteristic relaxation times τo, ψp, calculated from superposition of η versus\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}and ψ versus\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}data, respectively, onto Graessley's master curves, and τN, computed from zero shear parameters η0and ψ0, differ in their sensitivity to the melting of microcrystalline regions. It is postulated that in the systems investigated, aggregates with long lifetimes are being formed, increasing the effective molecular weight and introducing changes in th

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120310

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY