Liquid crystals under pressure: X-ray investigation of smectic <i>C</i> phases

Abstract

Under pressure P, the layer spacing of a smectic C phase, which is followed immediately by a nematic phase at higher temperatures, is found to be constant. In contrast, the layer spacing of a chiral smectic C, denoted smectic C*, which transforms to a smectic A phase at higher temperatures, changes dramatically as the pressure increases from the smectic C*−smectic A transition pressure Pc. If ϑ is the tilt angle, we find ϑ∼(P−Pc)β with β∼0.5, a classical result. We postulate that these two smectic C phases are stabilized by different intermolecular forces.