Thermal stability of internal electric field and polarization distribution in blend of polyvinylidene fluoride and polymethylmethacrylate

Abstract

It is confirmed that a melt-quenched and annealed blend of 80 wt % polyvinylidene fluoride and 20 wt % polymethylmethacrylate has the β-crystal form of PVDF with optical clarity and other properties that are desirable for a host material in a guest-host system where the guest is an optically nonlinear dye that is orientationally stabilized by the strong internal electric field of a poled ferroelectric. Combined measurements, in such a blend, of the internal electric field Ei, the pyroelectric coefficient Cpyro, and the polarization distribution after electrically poling and subsequently thermally aging for 2 h intervals at temperatures up to 120 °C are reported. Ei and Cpyro increase with increasing poling field Ep. Ei was found to be as large as three times Ep. An unexpected thermal stability of Ei was observed at annealing temperatures above the glass transition temperature of 60 °C up to 100 °C when significant loss of Cpyro was measured. Thermal pulse results yield polarization distributions that may be attributed in part to dipolar polarization and in part to space charge. The prolonged thermal stability of Ei is ascribed to space charge that does not contribute to Cpyro. The poled blend shows second-harmonic generation with a nonlinear coefficient d33 of around 1 pm/V (9×10−9 esu).