Smectic A twist grain boundary phase in three new series with chiral (L) lactic acid derivatives

Abstract

Three new series with a tolane core and a chiral L-lactic acid moiety have been synthesized. The theoretically predicted S_A-TGB_A-N∗ phase sequence is found in several compounds with short chains. The smectic A twist grain boundary phase (TGB_A) obtained with a cholesteric texture, is characterized by different techniques. Helical pitch measurements were performed using Grandjean-Cano wedges or homeotropic drops. All pitch values are lower than those found in previously reported series exhibiting the TGB_A phase. Ferroelectric smectic C (S∗_C) phases appear with long chains and have striated fan-shaped or pseudo-homeotropic textures. Electro-optical properties of the S∗_C phase were studied with the classical SSFLC geometry. We observed high polarization, slow response time and a saturated tilt angle of 20°. These results are comparable with previous studies.