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.