Density functional study of alpha-beta phase transition of polyvinylidene difluoride

Abstract

We perform density functional calculations to investigate structural and dynamical properties of crystalline polyvinylidene difluoride (PVDF) associated with the transition from a to beta phase. We examine the change of the conformational energy and the corresponding structure of each phase depending on the lattice parameters of the orthorhombic crystalline structure. From this information, we construct the path that connects the point where the a phase is most stable to the point where the beta phase is most stable, and identify the sub- region in the lattice parameter space where a and beta phases have the same energy. In this sub-region, we locate the point which gives the lowest conformation energy for both a and beta phases, and examine the behaviour of the lowest energy profile and corresponding change of intermediate structures as the conformation of the PVDF chain transforms from a phase to beta phase. Finally we perform ab-initio molecular dynamics simulations and analyse the characteristic dynamics associated with transition from a to beta phase. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)