Frozen Polarization of Piezoelectric Polyimides

We report a comparative frozen polarization study in three piezoelectric polymers: one polyimide without –CN dipolar groups (poly0CN), and two more that differ in the position of the –CN dipolar group present in the repetition unit (poly2-4 and poly2-6). The values of the dielectric permittivity and frozen polarization show that the participation of N-phenylphthalyimide group depends strongly on the curing process. For totally cured samples this group has little influence on the value of remnant polarization. The study was performed by dielectric measurements and by Thermally Stimulated Depolarization Current (TSDC) technique.