A new molecular ordering in helical liquid crystals

In the pursuit of new ferroelectric liquid crystals, a novel intermediary state of matter, the 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{prime}-(((4{double prime}-n-alkoxyphenyl)propioloyl)oxy)biphenyl-4-carboxylates. In these materials, the temperature at which the transition to the ferroelectric 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 the 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.