Use of Circularly Polarized Infrared Light to Liquid Crystals

This chapter describes the uses of circularly polarized infrared light in the field of liquid crystals (LC). VCD determined the chirality of a photoinduced segregated LC domain. The observed domain included an achiral bent-shaped dimer with azobenzene linkages. The results confirmed the occurrence of spontaneous resolution accompanied by the achiral-to-chiral transformation of a composite molecule. The molecular structures of a series of chiral metal complexes were investigated by VCD. They were used as a dopant inducing chiral nematic LC phases. When circularly polarized infrared light was irradiated on a chiral nematic phase doped with a photo-responsive Cr(III) complex, huge signals appeared apparently in the IR region. It was the selective reflection of circularly polarized light on a medium having a helically twisting layered structure. The phenomena were utilized for the real-time monitoring of the elongation of helical pitch length.