Synthesis and photoinduced birefringence of azobenzene-containing polymaleimides

Abstract

Azobenzene polymers having succinimide backbone structures were prepared and photoinduced birefringence of the polymers was investigated. Three functional maleimide monomers, N-4-[4-(phenylazo)phenylcarbamoyl]phenylmaleimide (1), N-4-[4-(4-nitrophenylazo)phenylcarbamoyl]phenylmaleimide (2), 2-[N-ethyl-4-(4-nitrophenylazo)phenylamino]ethyl maleimidobenzoate (3) were synthesized by reacting maleimidobenzoyl chloride with three azobenzene dyes, p-phenylazoaniline, disperse orange 3, disperse red 1 (DR1), respectively. Radical copolymerizations of the monomers 1, 2, and 3 with styrene, isobutyl vinyl ether, or methyl methacrylate were carried out to obtain soluble azobenzene-containing polymaleimides. The styrenic copolymers P1, P2, and P3 have high glass transition temperatures of 200, 175 and 150 degrees C, respectively. A different azo polymer, P4 was obtained by copolymerization of N-phenylmaleimide (PMI) with 3-isopropenyi-alpha,alpha-dimethylbenzyl isocyanate (IMSt) followed by a postreaction of the isocyanate prepolymer P(PMI/IMSt) with DR1. Upon irradiation of the amorphous films with linearly polarized light P3 and P4 rendered birefringence by induced optical anisotropy.