Preparation and characterisation of liquid crystal elastomer films with selective reflectivity

In this paper, the liquid crystal elastomer films (A’BG series) have been prepared by grafting polymerisation, using the 4-allyloxybenzoic acid cholesteryl ester (MB) as liquid crystal monomer, dodecane-1,12-diyl bis(undec-10-enoate) (MG) as flexible cross-linker and polymethyl hydrosiloxane (containing 35 Si-H) as the main chain. The A’BG series films are cholesteric liquid crystal elastomer films (LCEs) with a liquid crystal region above 100°C. With the crosslinker content decreasing, A’BG-2 and A’BG-3 display selective reflection in UV region and visible region, respectively. The selective reflection wavelength of A’BG-3 occurs blue shift with the temperature increasing. The glass transition temperatures (Tg) of the A’BG series films are 16.4–40.8°C and A’BG series films display shape memory properties near room temperature. The A’BG series elastomer films have a high thermal stability and the temperatures of the 5% mass loss are above 300°C. The backbone siloxane structures in the A’BG series elastomer films are highly stable, and the -COOChol group is relatively easy to decompose.