Side-chain cholesteric liquid-crystalline elastomers containing azobenzene derivative as cross-linking agent - synthesis and characterisation

The cholesteric polysiloxanes (PLQ series) were obtained by reacting cholesteric monomer and phenolic hydroxyl monomer in different ratios with polysiloxanes. The chiral azo-containing polysiloxanes liquid-crystalline elastomers (LCEs) were synthesised by esterifying PLQ series with acyl acid of azo diacid catalysed by 4-dimethylaminopyridine (DMAP). The chemical structures and mesomorphic properties of monomers and polymers were confirmed by conventional spectroscopic methods. The elastomers displayed elastic properties, reversible phase transition and high thermal stability. The T-g values changed irregularly and T-i values decreased at the beginning and then increased afterwards. The chiral azo-LCEs showed colourful textures and a Grandjean texture could be observed, which exhibited a red shift with increasing content of azo moiety. PLQ(2)-PLQ(6) exhibited selective reflection in the visible light region, but PLZ(1)-PLZ(4) can only observe selective reflection when appropriate mechanical pressure was imposed on the polymers. The PLZ series was carefully investigated by ultra violet-visible spectroscopy. [GRAPHICS] .