Reentrant smectic-Cand smectic-C*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-${\mathit{C}}^{\mathrm{*}}$ phases in the liquid crystal p-n-decyloxybenzylidene-p-amino-2-methylbutyl-cinnamate are reentrant with temperature for a range of electric fields. We show that the Landau theory with no 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 maximum in the pitch, unlike the reentrance under magnetic field. The Sm-C–Sm-${\mathrm{C}}^{\mathrm{*}}$ transition curve displays both main types of second-order phase transition, instability, and nucleation, separated by a first-order segment. p-azoxy-cinnamate-methyl-2-butanol and other compounds with divergent pitch should also show the double reentrance, but the physical origin is different.