Packing disorder in form 2 of poly(vinylidene fluoride): Influence of elongation and annealing temperature

Abstract

In the crystal structure of poly(vinylidene fluoride) form II, four molecules with different orientation occupy a crystal site with different probabilities. The crystallite of form II gives two kinds of antiphase domain structures, one on the c-projection and the other on the a-projection. The structural change of form II by elongation and annealing temperature can be explained in terms of the antiphase domain structures and the long- and short-range order parameters. Drawing of the sample produces the domain walls and forms the antiphase domain structure in the crystallite during the recrystallization process. Increasing elongation temperature diminishes the fraction and domain size of the minor component of the antiphase domain structure on the c-projection. Annealing below 160°C hardly affects this structure. As the annealing temperature is increased above 166°C, the fraction of the minor component and domain sizes of both minor and major components on the c-projection become larger. The disorder on the a-projection diminishes with increasing annealing temperature. On the basis of the antiphase domain structure, a mechanism for the change in molecular packing accompanying the transformation from form II to form III is discussed. © 1983 The Society of Polymer Science, Japan.