Structural changes in ferroelectric polymers under the action of strong electric fields by the example of polyvinylidene fluoride
- Troitsk Institute for Innovation and Fusion Research (Russian Federation), E-mail: kochval@orc.ru
The regularities of solid-phase polymorphic transformations under the action of strong electric fields in polyvinylidene fluoride (PVDF) films have been analyzed. For the homopolymer films crystallized in a mixture of nonpolar {alpha} and polar {beta} phases, two transitions are revealed: {alpha} {sup {yields}} {alpha}{sub p} and {alpha} {sup {yields}} {beta}. In contrast to predictions, these transitions occur simultaneously. For the isotropic PVDF films crystallized in the {alpha} phase, the critical fields corresponding to their transition to the ferroelectric {beta} phase may differ by almost an order of magnitude. It is suggested that nucleation of a new phase occurs through the fluctuation mechanism of formation of conformational defects (of the kink-bond type) in the initial crystals. Such processes are controlled to a great extent by the dynamics of through chains in the amorphous-phase regions adjacent to crystals when a decrease in their activation energy in the processes of micro-Brownian motion increases the probability of forming conformational defects in a crystal. If PVDF is crystallized in the ferroelectric phase, the action of strong fields leads to two consequences. First, according to the X-ray diffraction data, rotation of the polar b axes of a crystal through the mechanism of 60{sup o} reorientations is observed. Second, the degree of crystallinity can increase (partially irreversibly) through an increase in the crystal size.
- OSTI ID:
- 21091409
- Journal Information:
- Crystallography Reports, Vol. 51, Issue 1; Other Information: DOI: 10.1134/S1063774506070157; Copyright (c) 2006 Nauka/Interperiodica; Article Copyright (c) 2006 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7745
- Country of Publication:
- United States
- Language:
- English
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