REENTRANT SMECTIC-C AND SMECTIC-C-ASTERISK PHASES IN LIQUID-CRYSTALS UNDER AN ELECTRIC-FIELD

Kondo et al. [Jpn. J. Appl. Phys. 22, L43 (1983)] discovered that both the smectic-C and smectic-C phases in the liquid crystal ecyloxybenz ylidene-p-amino-2-methylbutyl-cinnamate are reentrant with temperature for a range of electric fields. We show that the Landau theory with n o adjustable parameters provides a semiquantitative explanation of the phase diagram. The double reentrance is due to two fourth-order terms , one chiral and the other achiral, and is intimately related to the m aximum in the pitch, unlike the reentrance under magnetic field. The S m-C-Sm-C transition curve displays both main types of second-order ph ase transition, instability, and nucleation, separated by a first-orde r segment. p-azoxy-cinnamate-methyl-2-butanol and other compounds with divergent pitch should also show the double reentrance, but the physi cal origin is different.