Piezoelectric, pyroelectric and ferroelectric polymers.

Biological and optically-active polymers show piezoelectricity when they have been subjected to a uniaxial drawing. Various polar polymers are both piezoelectric and pyroelectric if their dipole orientation is frozen-in after poling. Polyvinylidene fluoride and its copolymers are ferroelectric because their crystalline dipoles are switchable. They are therefore piezoelectric and pyroelectric. Polymeric materials belonging to these three categories are reviewed and basic mechanisms for these properties are discussed.