Influence of Interim Alkyl Chain Length on Phase Transitions and Wide-Band Reflective Behaviors of Side-Chain Liquid Crystalline Elastomers with Binaphthalene Crosslinkings

A series of side-chain polysiloxane liquid crystalline elastomers, E-Cm (where m is the number of carbon atoms in the interim alkyl groups, and m = 4, 6, 8, 10), with binaphthalene derivatives as crosslinkings, were designed and synthesized. The mesophase structures of these elastomers were dependent on the value of m. The elastomers with m <= 8 could form cholesteric (Ch) phases, while both smectic A and Ch phases could be formed for the elastomer with m = 10. Blue phases can be achieved when m >= 8. Besides, the helical twisting power (HTP) of all the elastomers exhibits a turning point with changing temperature. Both the turning temperature and HTP have an apparent dependence on the value of m. By adjusting the interim alkyl chain length in the elastomers, both visible and near-infrared light wide-band reflective films can be obtained. The broadband reflection mechanism was confirmed by SEM investigations.