Elsevier

Polymer

Volume 26, Issue 6, June 1985, Pages 821-826
Polymer

Polymer paper
Modelling of chain twist boundaries in poly(vinylidene fluoride) as a mechanism for ferroelectric polarization

https://doi.org/10.1016/0032-3861(85)90123-5Get rights and content

Abstract

It is assumed that the process of ferroelectric polarization of the beta phase of poly(vinylidene fluoride) (PVF2) in response to the action of the external electric field in direction perpendicular to the molecular axis and to the film, involves movement of the chain twist boundaries. These boundaries, at which every chain is twisted by 180 degrees, separate domains of opposite polarization. The energy barriers that are surmounted as the boundary was advanced one repeat unit were calculated and compared with the energy gained by reversing the polarization of an unfavourably oriented repeat unit in an electric field that produces polarization in PVF2. It is suggested that the movement of chain twist boundaries, in contradistinction to previously postulated models in which only one chain is twisted at a time, provides a model for the poling of PVF2 that is feasible energetically and kinetically. Theoretical modelling, analogous to that for Bloch wall that separates domains in magnetic materials, suggest that the process of polarization might be described either as a diffusion process or as the propagation of a soliton along the chains.

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