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 (PS = 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.