Unique sequence of phases was discovered in a chiral smectic, namely reentrance of orthogonal paraelectric A phase below the ferroelectric C phase. This behavior was explained by non-monotonous temperature dependence of the principal coefficient in the free energy expansion and microscopically by changes of molecular conformations and intermolecular distances due to occurrence a lateral bulky group in the molecule. This phenomenon is accompanied with anomalies in dielectric, optical and switching properties.
Stabilization of the reentrant phase was determined by mixing of the studied compound with the next homologues, which exhibit normal sequence without reentrancy. In the mixtures a direct transition between A and reentrant A phases was found, which can be understand as an analogy of crossover between liquid-like and gas-like behavior in supercritical fluids (widom-line phenomenon). The reentrant A phase can be easily influenced by electric field and exhibit strong electrooptic effect, which is promising for electrooptic application.
