Polymethacrylates with 3,3'- and 4,4'-Dihexyloxy Azobenzene Moieties in Side-Chains : Photoinduced Dichroism and Liquid Crystal Photoalignment

Abstract

Poly(methyl methacrylate) copolymers with 3,3'- or 4,4'-dihexyloxy azobenzene moiety were prepared through radical polymerization. Photoisomefization behavior and photoinduced dichroism of these copolymer films upon linearly polarized light irradiation were studied to reveal the effect of different conformational changes upon E/Z isomerization. The large photoinduced dichroism was observed for the polymer with 4,4'-substituents. Generation of the dichroism affords a photoalignment regulation of nematic liquid crystals in spite of as low as 7.0 % of the chromophore content. The direction of the dichroism is related to the direction of photocontrolled alignment of nematic liquid crystals. The conformational change of the chromophore during isomerization is assumed to be a crucial factor affecting molecular alignment.