Light sensitive antiferroelectric achiral copolymers

Abstract

Five copolymers were prepared by polymerization of azo-benzene methacrylate monomers in solution using AIBN as initiator. The mesophases were observed by a polarizing light microscope which showed tilted smectic C phases for almost all samples. One of them shows just one orthogonal smectic A₂ phase. The X-ray diffraction patterns reveal the existence of bilayer smectic C₂ mesophases. The spontaneous polarization and pyroelectric response are reported showing an antiferroelectric behaviour for three of the copolymers. The polar phase has to do with a preferable arrangement of side chains in a syndiotactic fashion, which promotes the formation of anticlinicity in the polymer net. We probe that it is possible to induce orientation of the chromophores subjected to irradiation with UV/Vis light and that it is proportional to the amount of monomers without the OH group within the copolymers. This is so far a unique manifestation of polar ordering due to the syndiotactic lateral distribution of mesogens bearing an OH group in a tilted smectic C₂ phase.