Successive Phase Transitions in Antiferroelectric Liquid Crystal 4-(1-methylheptyloxycarbonyl)phenyl 4'-octylcarbonyloxybiphenyl-4-carboxylate (MHPOCBC)

A new antiferroelectric liquid crystal (AFLC), 4-(1-methylheptyloxycarbonyl)phenyl 4'-octylcarbonyloxybiphenyl-4-carboxylate (MHPOCBC), was synthesized and an unidentified phase (designated as SmC x ) was observed between the paraelectric SmA phase and the antiferroelectric SmC A * phase by means of thermal, dielectric and electrooptical measurements. Thermal and dielectric studies suggest that the SmA-SmC x phase transition is of the second order and the SmC x -SmC A * phase transition is of the first order. Two types of electrooptical responses were observed in the SmC x phase: at relatively high temperatures the tristable switching appeared and at low temperatures tetrastables switching was noted. These features are discussed in terms of field-induced transitions.