CRYSTAL FORMS AND THEIR ORIENTATION IN POLY(VINYLIDENE FLUORIDE) FILMS PREPARED BY AN IONIZED-VAPOR DEPOSITION METHOD

Poly(vinylidene fluoride) (PVDF) films were deposited on substrates by an ionized-vapour deposition method under various conditions in which the acceleration voltage and ionization current were changed. IR spectra of the PVDF films were measured by IR reflection absorption spectroscopy methods with polarized light, and the crystal forms and their orientation in the films were investigated. It was found that the films containing form I crystals, which are known to possess ferroelectricity, were able to be obtained when ionization and acceleration were carried out. The contents of form I depended on both acceleration voltage and ionization current. The wattage supplied to the substrate (ion current multiplied by the acceleration voltage) seems to be a dominant factor in determining the crystal forms. From the result of IR dichroic measurements, it was found that the form I crystals were oriented; the molecular chain axes were parallel to the substrate surface, and the CF2 dipole was perpendicular to the surface and along the applied field. The film showed pyroelectricity, and its pyroelectric coefficient was about 1 nC cm-2K-1 which was a third of that of an authentic PVDF pyroelectric film. © 1990.