Characterization and Phase Transition Studies of Poly

Poly(vinylidene fluoride), PVF(,2), is known to exist in at least four crystalline phases. The various polymorphs can be produced by inducing crystal-crystal phase transitions in the polymer through a number of external forces. In this work, we will describe the morphological characterization which was carried out on three of the four crystalline phases. The phase II (--->) phase IV transition has been studied as well, and will also be presented in this work. The characterization includes infrared studies of the crystalline phases of PVF(,2), with particular attention paid to phase III. A normal coordinate vibrational analysis has been carried out in conjunction with the infrared studies. The crystal structure of phase IV ((alpha)(,p) or (delta) phase) has been determined. A model has been applied for which the chains pack in a statistical manner. The unit cell is found to be a primitive orthorhombic cell, with space group P2(,1)cn. Several groups have presented crystal structures for phase II ((alpha) phase) which have disagreed in some details. The crystal structure of phase II has therefore been re-examined, applying a statistical chain packing model. The unit cell is found to be a primitive orthorhombic cell, with space group P2cm. The phase II (--->) phase IV transformation and the reverse transformation have been examined utilizing dielectric capacitance and loss measurements. The infrared and x-ray techniques have been used as diagnostic tools in this phase transformation study.