Light-responsive patternable photonic cholesteric liquid crystal elastomers containing azobenzene and disulfide linkages

A light-responsive, mechanochromic, patternable, and photonic cholesteric liquid crystal elastomer (CLCEazo) has been developed by incorporating a dimethyl-substituted azobenzene diacrylate of 4,4 '-di(4-(acrylolylhexyloxy) benzoyloxy)-2,6-dimethylazobenzene (DADO) and a disulfide diacrylate of bis(2-hydroxyethyl) (ABES) via acryl thiol Michael addition reaction (ATMAR), during which a uniplanar orientation of the photonic structure was simultaneously achieved using the deswelling method. DADO and ABES in the photonic CLCE introduce light-responsive actuation and light-induced dynamic exchange reaction (DER), respectively. Photonic CLCEazo films prepared with the deswelling method has not been previously reported owing to the solubility problem of the azocompounds in organic solvents for ATMAR and deswelling. DADO introduction was facilitated by its increased solubility in nonpolar solvents suitable for ATMAR and deswelling which led the uniplar planar orientation for the photonic structure. UV light-induced DER between disulfide linkages mitigates stress generated during trans-to-cis isomerization and enables selective UV light photopatterning. These lightresponsive, patternable, and mechanochromic properties of the developed CLCEazo film are owing to combined effects of their photonic CLC structure induced by the deswelling method, DADO's cis/trans isomerization, and ABES's DER capability. These unique properties open new smart photonic applications of the CLCE triggered by light irradiation.