Change in crystallinity of poly(vinylidene fluoride) due to thermal evaporation

Dielectric properties are reported for thin transparent poly(vinylidene fluoride) (PVDF) films, with thickness less than 1 μm, obtained by the thermal evaporation technique. This technique had to be used with the utmost care and control over the temperature of the evaporation source to obtain transparent, undegraded films of PVDF. Capacitance and loss tangent measurements were carried out on these films in the frequency range of 20 Hz to 1 MHz and the temperature range of 25-160°C. It was found that the maximum in ϵ′-t plots at 1 kHz and tan δ-t plots at 100 Hz for these films appeared at 50 and 35°C, respectively, which are lower temperatures than those reported for solution cast PVDF films. This is attributed to the lowering of crystallinity in the thermally evaporated films. X-ray diffraction studies and IR studies also confirmed these observations. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 225–230, 1997