摘要:

AbstractThe lateral thermal motion of atoms in an inextensible polymer chain would cause a shortening along the chain direction. This effect could explain the observed negative thermal expansivity α along the chain direction of a polymer crystal. Using this idea, the expansivity α is calculated for a lattice of parallel linear chains. A value of −1.3 × 10−5K is obtained for chains with a carbon backbone, in good agreement with data for polyet

ISSN:0098-1273    

DOI:10.1002/pol.1980.180181201

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe mathematical solution of the following problem is given. Simultaneously with diffusion‐controlled mixing of two phases (e.g., gel formation), a third substance diffuses from one of the two pure phases into the other and through the inhomogeneous mixing phase which expands at a rate proportional to the square root of the time. The phases may change their volume

ISSN:0098-1273    

DOI:10.1002/pol.1980.180181202

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractHomogeneous films comprised of mixtures of polystyrene and poly(vinyl methyl ether) can be obtained by evaporation from a ternary solution containing toluene as the solvent. Heterogeneous films result when the solvent is trichloroethylene. The possibility that a heterogeneous film cast from trichloroethylene can be transformed to a homogeneous one by physical means is a logical expectation when the polymer‐polymer interaction is favorable, though as yet no comprehensive report has appeared in the literature. We have accomplished the transformation by increasing the temperature. Optical microscopy and glass transition experiments were employed to observe the effect

ISSN:0098-1273    

DOI:10.1002/pol.1980.180181203

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractReplicas and thin‐section electron microscopic studies were made of fractions of linear polyethylene covering the molecular weight range 2.78 × 104to 6.0 × 106for a variety of crystallizing conditions. Lamellar crystallites were found under all circumstances; and the supermolecular structure, or crystalline morphology, is in agreement with that previously reported from an analysis of the small‐angle light‐scattering patterns of the same samples under similar crystallization conditions. Details of the crystalline microstructure are also described, which range from truncated hollow pyramids which degenerate as the molecular weight or the undercooling are increased. From these results, it is possible to describe the mechanism of formation of polyethylene sphe

ISSN:0098-1273    

DOI:10.1002/pol.1980.180181204

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractA general equation for light scattering in multicomponent solutions is derived and applied to some important systems. The equation is compared with one published earlier by Casassa and Eisenberg [Adv. Protein Chem.,19, 287 (1964)], and the difference between them is explained.

ISSN:0098-1273    

DOI:10.1002/pol.1980.180181205

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe high‐pressure crystallization of polyethylene in a diamond cell has been studied by infrared spectroscopy. The splitting of the CH2rocking band at 720–730 cm−1as a function of pressure was analyzed. It was found that pressure alone up to 3 kbar will not change the distance between methylene groups in the unit cell. However, this distance can be shortened by crystallization at this pressure. Intensities of selected crystalline (1176 and 1050 cm−1) and amorphous (1303, 1352, and 1368 cm−1) bands were measured on samples before and after high‐pressure crystallization, and also on samples of various densities crystallized under atmospheric pressure. The increase in the intensities of crystalline bands and concomitant decrease in amorphous bands, together with density changes, indicate that the crystallinity can be enhanced by crystallization under high pressure. Nevertheless, the crystallinity of polyethylene crystallized at high pressure is comparable with that of polyethylene crystallized at atmospheric pressure at low undercooling for long peri

ISSN:0098-1273    

DOI:10.1002/pol.1980.180181206

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractSurface and interfacial activities ofA(B)2star‐shaped block copolymers, whereBis a polyoxirane block andAa polydiene or polyvinyl block, have been measured at 20°C. The surface tension of organic solvents is only slightly lowered by these copolymers, whereas a significant surface activity is noted in water. Interfacial tensions are dependent on both the nature of the organic solvent (aliphatic or aromatic hydrocarbons) and the molecular parameters of the copolymers; 50% polyoxirane seems to be the composition of maximum surface activity. The role played by the molecular architecture [A‐BorA(B)2] of the copolymers is demonstrated. The same limiting interfacial tension is obtained on increasing the concentration of diblock [A‐B] or star‐shaped block [A(B)2] copolymer. The limiting value is, however, attained at significantly lower concentration with the star‐shaped copolymers. Their ability to fill the interface is accordin

ISSN:0098-1273    

DOI:10.1002/pol.1980.180181207

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe considerable potential of high resolution time‐resolved spectroscopic data for copolymer systems in elucidation of the intramolecular photophysical processes which occur in polymer systems is illustrated. Such information can not be gleaned solely from studies of homopolymers. Kinetic data and time resolved fluorescence spectra of copolymers of 1‐vinylnaphthalene and methyl methacrylate indicate that conventional kinetic schemes are inappropriate for the discription of excimer formation in 1‐vinylnaphthalene polymers. Evidence is presented for the presence of an emitting species in addition to the expected monomeric and excimeric forms. The nature of this third species is discussed and photophysical kinetic schemes are proposed to describe intramolecular excimer formation in such systems. Kinetic data have been derived for the principle deactivation pathways through investigation of the observed fluorescence decays upon the intrachain concentration of aromatic sp

ISSN:0098-1273    

DOI:10.1002/pol.1980.180181208

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1980.180181209

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1980.180181210

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY