The characterization of a new helical smectic liquid crystal.

In the pursuit of new ferroelectric liquid crystals, a novel helical smectic A* mesophase was discovered. This layered phase was found between the isotropic liquid and the smectic C* phase in a variety of optically active R- and S-1-methylheptyl 4'- [(4"-n-alkoxyphenyl) propionoyloxy]-biphenyl-4-carboxylates. In these materials, the temperature at which the transition to the smectic C* phase occurs is relatively close to that of the clearing point. Moreover, the materials show a high degree of chirality. These two properties ensure that A* phase possesses relatively large molecular fluctuations which give rise to twist and bend distortions resulting in the stabilization of a helical structure. This new phase is apparently miscible with the classical smectic A phase, thereby classifying it as the chiral modification of the A phase.