Temperature dependence of piezoelectric constants for polyureas synthesized by vapor deposition polymerization

Thin films of aromatic and aliphatic polyureas are prepared by the evaporation and deposition of a diamine monomer and a diisocyanate monomer onto a polyimide substrate in a vacuum chamber. Application of a high electric field induces the films a residual polarization due to the alignment of urea bond dipoles. The piezoelectric constants for aromatic polyureas are almost unchanged from -150/spl deg/C to 200/spl deg/C. While those for aromatic polyureas show relaxational change due to the thermal molecular motions.