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.

摘要

制备了新的乳酸衍生物，并与我们之前研究的类似化合物相比，呈现了它们的介晶特性。研究的材料在从各向同性相 (Iso) 冷却时表现出胆甾相 (Ch) 和扭曲晶界 (TGB) 相。我们发现Ch相中的螺距相当短，小于可见光波长，并且在冷却时快速增长，因此在Ch-TGBA相变时，我们能够观察到可见光范围内的选择性反射。对于最长的同源物，检测到 Ch-TGBA-TGBC 相序。由于正介电各向异性，施加的电场沿场重新定向分子，并且在胆甾相和 TGBA 中间相中观察到类似于 Frederiks 跃迁的效应。