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

Abstract

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.

Keywords:

• selective reflection
• polymer stabilised liquid crystal
• temperature-dependent
• pitch gradient

Acknowledgements

The authors would like to express their gratitude for the financial support from the National Natural Science foundation (Grant No. 20674005), Major Project of the Ministry of Education of the People's Republic of China (Grant No. 104187) and Doctoral Fund of the Ministry of Education of the People's Republic of China (Grant No. 20050425850).