Phase behaviour of copolymers containing cholesterol and 4-methoxybiphenyl as mesogenic groups

Abstract

Abstract Liquid crystalline side group copolymers containing cholesterol and methoxybiphenyl were synthesized and investigated by size exclusion chromatography, 1H NMR, polarization microscopy, X-ray diffraction, differential scanning calorimetry and additionally by measuring the birefringence and the optical reflection of the cholesteric phase. This cholesteric phase could be obtained by copolymerization of two monomers whose homopolymers exhibit only smectic phases. The cholesteric phase exists over a broad range of copolymer composition. For the cholesterol containing homopolymer an SA2 bilayer phase was observed, whereas the methoxybiphenyl homopolymer shows a highly ordered E phase below an SA1 monolayer phase. The layer periods of the SA phases of the copolymers depend on the composition. By measuring the birefringence the order parameter in the cholesteric phase could be determined.