Electromechanics of a chiral smectic C elastomer: Measurement of complex piezoelectric constant through successive phase transformations

Piezolectric properties of a chiral smectic liquid crystalline elastomer and investigated by means of dynamic electromechanical measurements. We have confirmed that the piezoelectric constant is fairly large in the chiral smectic C (SmC*) phase. A relaxation of the piezoelectric constant is observed in the frequency dispersion curve of a director orientated elastomer obtained by a uniaxial deformation. The temperature dependence of the relaxation frequency in the smectic phases is nicely fitted to the Vogel-Fulcher-Tammann law, because the dynamics observed here is closely related to the glass transition phenomena. A resonance instead of a relaxation is recognized in the case of a biaxial deformed elastomer in which both layer and director are oriented to the their preferred directions. In addition, the piezoelectric constant of the biaxially deformed elastomer possessing a macroscopically spontaneous polarization is smaller than that of the uniaxially deformed elastomer with no net spontaneous polarization. We discuss the mechanism of polarization generation in the electromechancial response of the SmC* elastomers, and also consider the emergence of the resonance in the biaxial deformed elastomer.