摘要:

AbstractThe bond correlation function for a macromolecular model chain on a tetrahedral lattice is derived by considering elementary three‐bond and four‐bond motions. The method of calculation allows the conformational structure of the chain to be involved in the final equations. Moreover, when the three‐bond motions are considered alone, no linearization assumption is required; hence, the theory is valid at short

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130401

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractIn the preceding paper, general equations were established for the motions of chains confined to a tetrahedral lattice. In the present paper, bond orientation correlation and autocorrelation functions are explicitly calculated for the case where only three‐bond elementary motions are considered. Effects due to the chain end are analyzed and the relaxation time distribution function is established. The expressions obtained reflect the influence of the chain structure. Finally, to characterize the dynamic behavior of chains in orientation relaxation experiments, the notion of an independent kinetic segment is propose

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130402

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe elastic free energy for a tetrafunctional network is here expressed as\documentclass{article}\pagestyle{empty}\begin{document}$$ G_{{\rm el}} = C_1 \left( {\lambda _1 ^2 + \lambda _2 ^2 + \lambda _3 ^2 - 3} \right) + C_2 \left[ {\left( {\lambda _1 \lambda _2 \lambda _3 } \right)^m \left( {\lambda _1 ^{ - 2} + \lambda _2 ^{ - 2} + \lambda _3 ^{ - 2} } \right) - 3} \right] - \left( {{{C_1 } \mathord{\left/ {\vphantom {{C_1 } {C_2 }}} \right. \kern-\nulldelimiterspace} {C_2 }}} \right){\rm }\ln {\rm }\left( {\lambda _1 \lambda _2 \lambda _3 } \right) $$\end{document}where λ1, etc., are the principal extension ratios relative to the state of reference (wherein 〈r2〉 = 〈r2〉0), andC1,C2, andmare arbitrary parameters. The free energy of a swollen system is taken to be the sumG=Gmix+GelofGeland the free energy of mixing\documentclass{article}\pagestyle{empty}\begin{document}$ G_{{\rm mix}} = RT\left[ {n_1 \ln v_1 + n_2 \ln v_2 + \bar \chi n_1 v_2 } \right] $\end{document}. Stress‐strain relations and the chemical potential μ1are derived fromGas functions of the elasticity parametersC1,C2, andm, and of the thermodynamic interaction parameterχor of\documentclass{article}\pagestyle{empty}\begin{document}$\chi = \bar \chi + n_1 v_2^{ - 1} \partial \bar \chi /\partial n_1 $\end{document}. The dilation of the semi‐open system subject to deformation when exposed to diluent at fixed activity is derived as the sum of the dilation at fixed composition and the dilation due to absorption of diluent. Experiments are reported on the dependence of the equilibrium retractive force on elongation for cross‐linked polydimethylsiloxanes (PDMS) exposed to benzene or hexamethyldisiloxane vapor at regulated activities. Volume fractions of samples covered the rangev2= 1.00 tov2≈ 0.30. With the choice ofm= ½ the elastic behavior of a given polymer is well represented by one combination of values forC1andC2at all dilutions by either diluent. The dependence of the Mooney‐Rivlin (C2) term on volume is thus established, at least for PDMS, and the scope of the semi‐empirical free energy expression and its consequents is greatly enlarged. Values of χ deduced from the equilibrium swelling of the unstrained networks exposed to benzene at various activities are in excellent agreement with those obtained previously from vapor pressures and osmotic pressures on linear PDMS. The results of Allen, Kirkham, Padget, and Price on the elastic behavior of natural rubber are discussed, with particular reference to the coefficients of dilation with elongation which they determined at fixed composition. The present results lend strong support to the principle of additivity of the free energies attributable to the network and to the bulk liquid system, respectively. This principle is fundamental to the analy

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130403

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractStress relaxation and moduli of elasticity of the composite system crosslinked poly(2‐hydroxyethyl methacrylate) (PHEMA)–glass beads were studied dry and swollen in water to equilibrium state over the temperature range 5–170°C. The moduli of the composites in the dry state increased with increasing filler concentration, while those of the composites measured in the swollen state up to the volume concentration of the fillerv f′≅ 0.15 decreased. In this respect the composites behaved as porous systems, i.e., as polymers with macroscopic defects. This effect was explained as a consequence of weak filler–matrix interaction. The results were compared with the existing theories of moduli of the compo

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130404

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe method of density and refractive index increments was used for the determination of the coefficients of selective sorption of acetophenone and bromoform on polymer in the system poly(methyl methacrylate)–isopropanol–acetophenone–bromoform as a function of the composition of the ternary solvent. In systems containing more than 80% by volume of bromoform the precipitant—isopropanol—is selectively sorbed. The conditions under which the method gives satisfactory results and some methodological problems of densitometry have been

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130405

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe fluctuation theory of light scattering for moderately concentrated polymer solutions is extended in a phenomenological fashion to include angle‐dependent terms up to sin2(θ/2). The treatment is based on an uncoupling of the center of mass and segment contributions to the free enthalpy. In particular, equations are derived for three‐component mixtures containing two polymer and one solvent component. These are applied near the region of incompatibility. The results are compared with Debye's theory of critical opalescence. It is found that the Debyelparameter should be of the order of magnitude of the radii of gyration of the polymer molecules. This is confirmed by some experim

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130406

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractMeasurements of dielectric constant and loss, broad‐line nuclear magnetic resonance, and differential thermal analysis of concentrated solutions of poly(γ‐benzyl‐L‐glutamate) (PBLG) were carried out to determine the effects of intermolecular interactions on the mobility of the side group and the solvent (dichloromethane or dioxane). Only one dielectric loss peak due to the cooperative motion of the side group and the solvent was found. The activation energy of this relaxation process varied from 3 to 47 kcal/mole with increasing concentration of PBLG from 20 to 100% by weight accompanied with steep increases at about 40 and 80%. This result is explained as due to entanglement of neighboring side groups. In NMR, narrowing of the line was observed near the temperature where the dielectric loss was observed. The glass transition was also observed by differential thermal analysis. From these results it was concluded that the relaxation observed in PBLG solution and in pure PBLG have the nature of primary or α re

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130407

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe crystal structure of the monomer bis(p‐toluene sulfonate) ester of 2,4‐hexadiyne‐1,6‐diol (pT) is conducive from the viewpoint of both the separation distances and molecular configuration, to polymerization, irrespective of whether initiation is thermal, photochemical, or mechanical. The dislocations present in the monomer and polymer structures have been characterized by employing optical microscopic techniques. The slip system (102)[010] is found to be present in both monomer and polymer crystals but the (010)[001]system is found only in the monomer. On this basis a crystal structure for the monomer is proposed based on existing crystallographic information relating to the structure of the polymer. Dislocations are thought, on energetic grounds, to facilitate nucleation of product in the thermal polymerization but have no observable influence on the photoinduced reaction which proceeds homogeneously through t

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130408

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractTo investigate the morphology of unoriented poly(ethylene terephthalate) (PET) films and the selective character of the aminolysis of PET, 67% crystalline polymer samples were degraded with 40% aqueous methylamine at room temperature. The aminolyzed PET samples were subjected to gel permeation chromatography (GPC), viscometry, electron microscopy, and small‐angle x‐ray diffraction (SAXD). Weight loss and density crystallinity measurements were also made.After 24 hr of aminolysis, the amorphous regions and chain folds were completely removed. The long molecular chains in the semi‐crystalline polymer were reduced to monodisperse rods having a molecular weight of 1,800. The corresponding lamellar thickness was calculated to be 101 Å, consistent with the x‐ray diffraction and electron microscope (EM) measurements. The EM photographs of “stripped” crystals show the lamellar structure previously found for other selectively degraded polymeric materials. The weight of crystalline debris remaining was consistent with the initial crystallinity. After degradation the crystallinity as determined by den

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130409

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe relaxation modulusG(t) and the stress decay after cessation of steady shear flow were measured on concentrated solutions of polystyrenes in diethyl phthalate. Ranges of concentrationcand molecular weightMof the polymer were from 0.112 to 0.329 g/ml and from 1.23 × 106to 7.62 × 106, respectively. The relaxation spectrumH(τ) as calculated fromG(t) for the solution of very highMwas found to be composed of two parts. One, at relatively short times, was a broad distribution (plateau zone) with height proportional toc2. The second, at the long‐time end, was very sensitive to concentration and gave rise to a maximum inH(τ) for very high concentrations. The behavior ofH(τ) at long times was examined quantitatively by evaluating the longest relaxation time τ10and the corresponding relaxation strengthG10fromG(t) and from the stress decay function, on the assumption of a discrete distribution of relaxation times at long times. The longest relaxation time was approximately proportional toM3.5, even at relatively low concentrations where the zero‐shear viscosity was not proportional toM3.5. The strengths of relaxation modes with the longest few relaxation times are proportional to the third power of conc

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130410

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY