Effect of crystallinity on the dielectric behavior of poly(vinylidene fluoride) in the region of glass transitionстатья
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Дата последнего поиска статьи во внешних источниках: 28 мая 2015 г.
Местоположение издательства:Road Town, United Kingdom
Первая страница:954
Последняя страница:959
Аннотация:The relaxation of PVDF films with various thermomechanical prehistory was studied in the region of glass transition by the dielectric method. The relaxation time of the microscopic Brownian motion in the amorphous phase decreases abnormally with the increasing degree of the polymer crystallinity. This effect is connected to discontinuities in the packing density within disordered regions caused by the formation of thicker lamellae. The resulting increase in the free volume leads to the decrease in relaxation time. For the textured films, the increment of dielectric absorption increases markedly upon the sample orientation. The results of spectroscopic measurements showed this to be due to an orientation-induced conformational transition of the type (GG) → (TT)n, with the latter isomers having a higher transverse component of dipole moment. The thermodynamic analysis based on the temperature dependence of the static permittivity suggests the possible formation of regions with a correlated arrangement of the polar segments - quasidomains. The interactions are assumed to have a long-range nature, while the character of chain packing in the quasidomains is suggested to be of the nematic type.