摘要:

AbstractThe physical structure of Nafion membranes has been investigated by small‐angle neutron scattering (SANS) and small‐angle x‐ray scattering (SAXS). Samples in the acid form may exhibit two scattering peaks. The first, observed by SANS at an angle corresponding to a Bragg spacing of 180 Å, is shown to arise from structures in crystalline regions. A second peak at larger scattering angles is shown to arise from ion‐containing regions which may be swollen with water. Salt‐form samples made by soaking the acid form in an aqueous salt solution can also exhibit the same two scattering signals. But in amorphous salt‐form samples produced by quenching from the melt the first peak is absent. This permits a more accurate study of the second peak by SAXS, which shows that the second scattering component is present as a maximum over a wide range of water contents but is absent in a sample dried at 200°C. The position of the peak shifts to lower scattering angles (or larger spacings) at higher water contents. Possible structural models that might give rise to the maximum are discussed. A calculation of the SAX invariant is made and results are consistent with a phase separation of a large fraction

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190101

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractIt is shown that the13C NMR spectral collapse temperaturesTcreported by Axelson and Mandelkern tend to give a constant ratio ofTc/Tgaveraging 1.21 ± 0.05 and independent ofTgor of polymer structure. It is further shown thatTcis not a high‐frequency value forTgbecause this would requireTc/Tgto decline with increasingTg.Tc/Tgagrees in numerical value withTu/Tg, whereTllis the liquid‐liquid transition lying aboveTg. Direct comparison ofTcandTufor four polymers PIB, PnBA, atactic PP, and isotactic PMMA shows very close agreement. The various results suggest, but do not prove, thatTcfrom13C NMR spectroscopy may be a new, direct measure forTll. A measuredTcof 233K for linear PE is compatible with aTgnear 195 K (233/195 = 1.19), whereas aTgof 148 K gives the ratio 233/148 = 1.57, which is outside any value shown in tabulated

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190102

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe effect of a heterogeneous chlorosulfonation on the crystalline regions of high‐density polyethylenes are investigated by x‐ray diffraction, differential scanning calorimetry, and infrared spectroscopy. The observed changes and their time dependence are discussed in terms of distortion of the crystallites, which is followed by relaxation processes leading to the elimination of the initially induced imperfecti

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190103

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractHalf‐crystallization timest½, enthalpies of fusion ΔH, melting temperaturesTfglass transition temperaturesTgx‐ray patterns, and morphologies were obtained for nine samples of poly(α‐methyl‐α‐n‐propyl‐β‐propiolactones) prepared from different homogeneous or heterogeneous initiators. The bulk of the results indicates that all samples can be classified into two categories: Polymers A havingt½≏, 100 min, ΔH≏ 26 J/g,T f0≏ 376 K, Tg≏ 275 K, and Polymers B havingt½≏ 10 min, ΔH≃ 14.5 J/gT f0≏ 425 K and Tg≏ 271 K. PolymersAwere prepared with homogeneous initiators while polymersBwere polymerized with heterogeneous intiators. The difference in crystallization behavior between polymersAand polymersBis certainly due to a difference in microstructure, brought about by the initiators,

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190104

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractA theory is presented to account for the effect of the impingement of growing spherulites on theirHvsmall‐angle light scattering patterns. The theory is developed on the basis of results of computer‐simulated two‐dimensional spherulite growth and calculated scattered intensities. The impingement produces a lowering of the intensity of the scattering maximum and the diminishing of the overall sharpness of the scattering peak. The extent of these effects increases with area fraction of spherulites. A procedure is suggested for determining correction factors that may be applied to intensity data obtained during the course of spherulite crystallization. An interpretation is made of the type of average spherulite size determined from the scattering angle of maximum inte

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190105

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractEffects of interparticle interference on depolarized light scattering from polymer films having nonspherulitic (rodlike, disklike, or fibrous) crystalline superstructures are explored, both theoretically and experimentally. Discrepancies between the observed “rodlike scattering” and the predicted scattering based on “single‐rod” theory are pointed out and accounted for in terms of various types of aggregation models for polymeric solids and

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190106

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractWe have measured1H and19F NMR relaxation timesT1,T1ρ, andT2, and diffusion constants, in trace penetrants hexafluorobenzene andn‐hexadecane dissolved in stretchedcis‐polyisoprene, as function of temperature, rubber elongation, and angle with respect to the stretch direction. Values ofT1andT2in the rubber were also measured. At all temperatures (—40 ≤T≤ 85°C),T1in rubber and penetrants is isotropic and independent of elongation; the differences between rubber and penetrants are related to penetrant diffusion. AllT2above—15°C are anisotropic and elongation dependent, and follow a motional narrowing model. For the penetrants, averaging the dipolar interactions implies averaging over a diffusion path; this correctly reproduces the observed much higherT2anisotropy in the penetrants. Penetrant diffusion rates, however, are essentially isotropic and elongation independent. These effects depend only weakly on the shape of the penet

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190107

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractMost methods of studying molecular orientation in polymers can give only limited information about the distribution of molecular orientations, and this is particularly true of methods for studying the noncrystalline material. It is shown, however, that if the mean valuesP2andP4of the second‐order and fourth‐order Legendre polynomials in cosθ can be determined for the chains in a uniaxially oriented polymer, where ‐ is the angle between the chain axis and the drawing or extrusion direction, some qualitative statements about the form of the distribution can be made with complete certainty for some, but not all, sets of values ofP2andP4. It is shown in addition, that if the distribution is fairly smooth a good estimate of its general form can also be obtained, and that a knowledge ofP6and higher‐order means will not improve this estimate appreciably unless they are known with great

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190108

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractBroad‐line1H NMR spectra of linear polyethylene at temperatures in the α‐transition range can be analyzed in terms of contributions from the crystalline and noncrystalline components provided molecular motion in the crystalline region is adequately considered. The spectrum of solidn‐C32H66orn‐C44H90prior to melting is used to take account of the contribution of the crystalline region of the polymer to molecular motions. The temperature dependence of the component distribution in the polymer is briefly discussed for a wide range of temperatures, together with previously reported results at low temperatures. The noncrystalline component is in a rigid glassy state at very low temperatures but with rising temperature it transforms to a mobile glassy state with restricted molecular motion, and transforms partially to the rubbery state at high temperature. The crystalline component remains rigid at low temperature, but some molecular motion is associated with it at higher temperatures in the α‐trans

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190109

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractTypes of nylon 6 yarn which contain large γ crystals cannot be described by a model comprising three Pearson VII curves, as we formerly proposed. Hence, a new extended computer program has been developed containing five Pearson VII lines. Two lines are related to the α phase, two to γ‐phase crystals, and the fifth describes the amorphous contribution. Some physical relations between parameters could be derived and were incorporated into the computer program. This program provides extremely good fits to all equatorial diffractometer scans which can be obtained from nylon 6 yarns, including those containing large γ crystals. The parameter accuracy is quite satisfactory for diffractometer traces with well‐resolved peaks from both α and γ crystals. However, if the traces are poorly resolved or the samples do not contain a sufficient amount of the γ modification, resulting in a lack of detailed information, the parameter accuracy can be rather poor. For those cases special versions of the computer program were developed which contain further empirical interrelations between parameters. With these programs crystal sizes and molecular distances within the crystals of both the α and β modifications can be determined. The method has also been applied to radial scans at various small azimuthal angles with respect to the equator. In that way the relative amounts of the α and γ crystals as well as their orientation factors could be determined. Various aspects of this investigation are illustrated by

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190110

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY