Raman scattering studies of phase transitions in ester ferroelectric liquid crystal

Temperature dependence of the Raman spectra of ester ferroelectric liquid crystal MBOPDOB are examined in all four phases. The 15 and 49 cm(-1) modes vanish at crystal-smectic CI transition point without any detectable frequency shift, which is classified into an order-disorder category. All the results which include small transition heat, the 93cm(-1) mode and the spontaneous polarization continuously going through the transition point, and the 1178 and 1710 cm(-1) modes being transferred to 1166 and 1738 cm(-1), respectively, manifest a continuous second-order transition for the Sm C*-Sm A which is closely related to large temperature range of the Sm A phase and small spontaneous polarization.