Discontinuous Change in Density at Phase Transition in Antiferroelectric Liquid Crystal

Abstract

Discontinuous changes in density (Δρ) at various phase transitions in an antiferroelectric liquid crystal, 4-(1-methylheptyloxycalbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC), were estimated using published data and the Clausius–Clapeyron equation. The estimated Δρ at the SmCFI1*–SmC* transition is about twice as large as that at the SmCA*–SmCFI1* transition. This result suggests that the changes in density at these phase transitions are related to the disappearance of the interdigitation of molecules. As a result of reconfirming the data for 4-(1-metylheptyloxycarbonyl) 3-fluorophenyl 4'-dodecylbiphenyl-4-carboxylate (MHFPDBC), a change in density of -2×10-5 g/cm3 was detected at the Ferri–SmC* transition in MHFPDBC.