Study of selectively reflecting characteristics of polymer stabilised chiral nematic liquid crystal films with a temperature-dependent pitch length

Chiral propane-1,2-di-(4-(4-heptylcyclohexyl)benzoate) (PPCB) and 1-phenylethane-1,2-di-(4-(4-heptylcyclohexyl) benzoate) (PEPB) were synthesised and used as chiral dopants to induce chiral nematic liquid crystals (N*-LCs). Since the helical twisting power of the former first decreased and then increased as a result of thermally induced inversion helicity sense, and those of the latter changed little with increasing temperature, the pitch lengths of the N*-LCs prepared from (N-LC)/PPCB/(R)-PEPB and N-LC/PPCB/(S)-PEPB mixtures decreased and increased with increasing temperature respectively. Then, based on these two kinds of N*-LCs, polymer stabilised liquid crystal films were obtained, in which the bandwidth of the selective reflection spectra increased with increasing temperature.