Azobenzene Liquid Crystals with High Birefringence and Their Effect of Trans-Cis Photoisomerization on Selective Reflection

Abstract

A series of four novel azobenzene liquid crystals (LCs) with high birefringence were synthesized by coupling of intermediate molecules with a phenylacetylene fragment. The chemical structures of synthetic intermediates and compounds were confirmed by FT-IR and 1H-NMR. The LC behavior including transition temperatures and phase sequences were investigated by differential scanning calorimetry (DSC) and polarizing optical microscope (POM). As a very important parameter, the birefringence was also measured using polarizing light interferometry method. Moreover, the characteristics of selective reflection which was associated with the birefringence of the N*-LC dropped with azobenzene LCs and the effect of trans-cis photoisomerization of these compounds on selective reflection were studied in detail.