摘要:

AbstractWe calculate the elastic scattering of a long chain in a polymer melt during the process of relaxation after a sudden deformation, i.e., the return to equilibrium with time, while the deformed shape is maintained. The scattering thus depends on the durationtof the relaxation, as well as on the scattering vector, and is a physical quantity characteristic of the dynamics of long chains. The reptation model of de Gennes is used as developed for deformed melts by Doi and Edwards: the chain is confined by other chains in a tube, from which disengagement by the ends is the only way of renewing its configuration. The tube diameter is taken as a parameter. We give both an analytic form and numerical evaluations. On comparison with calculations based on the Rouse model, in which the chain is assumed to be free in a viscous medium, it is seen that the experimental data (given elsewhere) should enable one to distinguish between the two models.

ISSN:0098-1273    

DOI:10.1002/pol.1985.180230501

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractFourier‐transform infrared spectroscopy was used to characterize the thermal polymerization of the acetylene‐terminated (AT) resin, bis[4‐(3‐ethynylphenoxy)phenyl]sulfone. Spectral processing techniques (including the method of factor analysis) were utilized in the analysis of the infrared data. The degree of cure was quantitatively monitored as the resin was thermally polymerized. Factor analysis indicated that only one reaction product is spectroscopically distinguishable. Further band analysis indicated the formation of predominantlytransconjugated polyene structures. No evidence for cyclotrimerization wa

ISSN:0098-1273    

DOI:10.1002/pol.1985.180230502

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe use of band‐ratioing techniques in internal reflection spectroscopy (IRS) for a wide variety of polymer surface composition and orientation measurements is discussed. It is shown that quantitative data can be obtained under a wide range of experimental conditions. The effects of variations in sample contact, internal reflection element, and angle of incidence are considered in detail. The applicability and limitations of calibration procedures for the determination of surface composition under various experimental conditions are considered. The requirements for obtaining quantitative results by IRS are shown to be far more lenient than is typically assume

ISSN:0098-1273    

DOI:10.1002/pol.1985.180230503

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractWe further examine the mechanisms involved in the emission of electrons and positive ions from polybutadiene accompanying fracture. Experimental evidence is given in support of a previously presented model involving a microdischarge accompanying fracture which excites the fracture surfaces by particle bombardment. Calculations of the time dependence for the emission from such excitations for both isothermal and thermal stimulation from a simple trap model are presented. We conclude that both filled and unfilled polybutadiene are experiencing the same excitations except at a considerably reduced intensity for the unfilled material.

ISSN:0098-1273    

DOI:10.1002/pol.1985.180230504

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe thermally stimulated‐current method (TSC) has been employed to determine the temperatures and intensities ofTβ,Tg, andT>Tgfor pure isotactic, pure syndiotactic, and five atactic specimens with syndiotactic triad content from 49.5 to 75%;Tgwas found to increase linearly with syndiotactic triad content asTg(°C) = 48.0 + 0.856 (% syn), withR2= 0.970 standard error 5.6°C;Tgfor the syndiotactic specimen is 136.6°C measured, 133.6°C calculated. Several atactic specimens exhibit a second glass temperature 15 to 35 K above the regression line ascribed to some pure syndio content, and/or some isotactic–syndiotactic stereocomplexes. All specimens exhibited the liquid–liquid orTLLtransition (relaxation) which increases linearly with 100‐% isotactic triad content. Isotactic PMMA shows aT′LLrelaxation 50 K aboveTLL. TheTgandTLLvalues obtained correlate extremely well with values from differential scanning calorimetry (DSC) determined in a separate study, as well as with most literature data. Intensities ofTgandTLLby TSC are greatest for isotactic, next for syndiotactic, with a broad, low minimum for atactic materials. The intensity of a β relaxation increases slowly from isotactic to syndiotactic. TheTLLfound by TSC compares well with literature values for isotactic PMMA obtained by several methods, andTLLin the atactic region compares well with literature values for atactic material. The ratioTLL/Tgranges from 1.09 to 1.20 with no dependence on tacticity.Tgfollows simple Arrhenius behavior with enthalpies of activation about one‐half of the values normally calculated from dielectric and mechanical loss. The frequency dependences ofTLLandT′LLfollow a Vogel–WLF relationship with temperature. The origin ofTLLis discussed in terms of the Frenkel hypothesis of segment–segment interaction. Evidence forTLLandTLLfrom a variety of methods indicates that these two temperatures are not arti

ISSN:0098-1273    

DOI:10.1002/pol.1985.180230505

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA method is presented for the calculation of cloud‐point curves of polymer–polymer mixtures when the polymers involved are polydisperse. The method is based on the Flory–Huggins free energy of mixing with a concentration‐independent χ parameter. Numerical results are given for cases in which the molecular weight distributions are represented by the Schulz–Flory type. When the two polymers have similar average molecular weights and polydispersities, the cloud‐point curves become flatter as the polydispersity increases. When the two polymers have similar average molecular weights but differ in polydispersity, the cloud‐point curves become more skewed as the difference in the polydispersity increases. The results point out that, if the polydispersity effect is not properly accounted for, the value of χ deduced from experimental cloud points is liable to be in error, especially with regard to its temperature coefficient and its concentra

ISSN:0098-1273    

DOI:10.1002/pol.1985.180230506

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe variation of refractive index increments with molecular weight has been studied using solutions of polystyrene (2.2 × 103

ISSN:0098-1273    

DOI:10.1002/pol.1985.180230507

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractPercolation and effective‐medium theories are applied to model the transport and elastic properties of perfluorinated ionomers. The composite nature of these polymers is emphasized. The effective‐medium theory is generalized to track continuously the evolution from lamellar to fibrillar morphology. The predicted dramatic difference in ion selectivity between lamellar and spherical morphology is verified quantitatively in perfluorinated ionomer blends. The limitations and potential improvements of the effective‐medium theory and its relationship to percolation theory are discussed. Applications of these theories to other multiphase polymer systems are also disc

ISSN:0098-1273    

DOI:10.1002/pol.1985.180230508

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe theory of Freed and Edwards is used to investigate polymer migration in nonhomogeneous flow fields with confined geometry. Polymer migration from the main flow originates in three effects: (i) nonhomogeneous flow‐field effect, (ii) the confined‐geometry effect, and (iii) the concentration effect. General correlation function formulas for these three effects are explicitly derived. Some specific examples are illustrated and solved by using the harmonic dumbbell and Rouse–Zimm m

ISSN:0098-1273    

DOI:10.1002/pol.1985.180230509

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractSorption and diffusion of toluene vapor in linear polyethylene with mass‐fraction crystallinity between 0.48 and 0.82 and draw ratios λ up to 10 have been studied at 30°C. The sorbed concentration in the amorphous phaseCais little affected by crystallinity, indicating that the free‐volume fraction is roughly the same for all isotropic samples. However, the diffusion path becomes more tortuous with increasing crystalline content, thereby leading to a sixfold drop in the zero‐concentration diffusion coefficientD0. Drawing has more drastic effects, reducingCaandD0by factors of 4 and 60, respectively, as λ increases to 10. These large changes result from the transformation of the initially spherulitic material into a fibrous structure, which is composed of aligned microfibrils with taut tie molecules lying on the outer boundaries. The effects of crystallinity and orientation on the concentration dependence of the diffusion coefficient are also d

ISSN:0098-1273    

DOI:10.1002/pol.1985.180230510

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY