Reentrant synclinic phase in an electric-field–temperature-phase diagram for enantiomeric mixtures of an antiferroelectric liquid crystal

The threshold electric field E(th) for a transition from the anticlinic to the synclinic phase of enantiomeric mixtures of the liquid crystal TFMHPOBC was measured as a function of temperature T and enantiomeric excess X. For small X the phase boundary curve on a temperature-electric-field phase diagram exhibits the phase sequence synclinic-anticlinic-reentrant synclinic on decreasing the temperature. At one point along the curve the quantity dT/dE--> infinity. For large values of enantiomeric excess a reentrant phase is not observed. The results are discussed using a simple phenomenological theory that accounts for layer-layer interactions, such that the electric-field-induced transition to the synclinic phase, although completed by solitary-wave propagation, is facilitated by a percolation mechanism.