Piezoelectric and pyroelectric properties of new polysiloxane smectic C elastomers

We investigated the pyroelectric and piezoelectric effects of new smectic C^* liquid crystalline elastomers. The materials are made up of a flexible polysiloxane backbone bearing chiral mesogenic side groups and are cross-linked via alkylene chains. The polar structure of the mesophase is evidenced by the observation of piezoelectric and pyroelectric effects. Integration of the pyroelectric coefficient over the whole smectic C^* stability range allows the determination of the spontaneous polarization (P_S = 3–6 nC/cm²). Due to the rubber elasticity, these materials exhibit a high piezoelectric response. The piezosignal at room temperature does not vanish after annealing at temperatures even much higher than the Curie point. The piezoelectric coefficient d₃₁ ranges from 0.5 pC/N for non-poled samples to 2.5 pC/N after application of a poling field.