The cholesteric and TGB phases under the applied electric field

Abstract

ABSTRACT New lactic acid derivatives were prepared and their mesomorphic properties presented in comparison with analogous compounds we pursued previously. Studied materials exhibit cholesteric (Ch) and twist grain boundary (TGB) phases on cooling from the isotropic phase (Iso). We found the helical pitch in Ch phase was rather short, less than the visible light wavelength, and grew quickly on cooling, so at the Ch-TGBA phase transition, we were able to observe the selective reflection in visible range. For the longest homologue, the Ch-TGBA-TGBC phase sequence was detected. Due to the positive dielectric anisotropy, the applied electric field reoriented molecules along the field and the effect analogous to Frederiks transition was observed in cholesteric and TGBA mesophases. X-ray diffraction measurements were performed to unambiguously confirm the phase identification.