Dielectric relaxations and molecular motions in poly(vinylidene fluoride) with crystal form II

Abstract

AbstractMolecular motions in poly(vinylidene fluoride) were studied by dielectric measurements. Of the three relaxation processes, the αa and the αc were studied. The αa relaxation was attributed to the molecular motions in the amorphous regions and the αc relaxation to molecular motions in the crystalline regions and their surfaces. The relaxation time and the magnitude of the αa absorption were analyzed on the basis of the Adam‐Gibbs theory of the temperature dependence of the size of the cooperatively rearranging region. As a result it was concluded that the molecular structure of crystal form II holds locally, even in the amorphous regions. The relaxation time and the magnitude for the αc absorption were analysed on the basis of the two‐site model. It was concluded that the αc relaxation is attributable not only to molecular motions in the folds of the lamellar crystals, but also to those in the interior of the crystal; the folded chain is relatively mobile, while the molecular chain in the interior of the crystal executes restricted rotation around the chain axis.