A Comparative X-Ray Diffraction Study of Two Liquid Crystalline 2,5-Disubstituted 1,3,4-Oxadiazole and 1,3,4-Thiadiazole Derivatives in Their Smectic Phases

Abstract X-ray diffraction study of two liquid crystalline 2,5-disubstituted 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives reveals the existence of a partially bilayered smectic Ad phase in the terminally bromo substituted derivatives, with the lower level of molecular overlapping in the formation of the dimer and more pronounced smectic fluctuations on the dimeric density wave observed for the former compound.