Broadband dielectric investigations on a compound consisting of bent-shaped molecules

Dielectric measurements on the antiferroelectric smectic C (SmCPA) and isotropic (I) phases of a substance formed by bent-shaped molecules were performed in the frequency range from 0.1 Hz to 0.1 GHz. Three absorption ranges, corresponding to a slow collective process, the reorientation of the molecular core around the long axes and the fast dynamics of the terminal groups, were detected in the SmCPA phase, whereas only two ranges, related to the two last processes, appear in the isotropic state. At the I-SmCPA phase transition the process of molecular reorientation around the long axes changes stepwise with respect to the absorption band intensity and the relaxation time, while the activation energy remains practically unchanged. The activation energy for the dynamics of the terminal groups increases at the I-SmCPA transition.