Improvement of photoinduced birefringence properties of optically active methacrylic polymers through copolymerization of monomers bearing azoaromatic moieties

Optically active photochromic copolymers of different composition, deriving from the conformationally rigid chiral monomer (S)-3-methacryloyloxy-1-(4'-nitro-4-azobenzene)pyrrolidine [(S)-MAP-N] and the isosteric and isopolar methacrylic ester of the flexible achiral chromophore 4'-[(2-hydroxyethyl)ethylamino]-4-nitrobenzene [DR1M], have been prepared and characterized in solution and in the solid state with the aim to investigate the effect on their thermal and chirooptical properties originated by the presence of isosteric and isopolar azoaromatic moieties in the side chain. The photoinduction of birefringence has been assessed on films of the investigated copolymers in order to evaluate their behavior as materials for optical data storage. The results are interpreted in terms of copolymer composition and different cooperative behavior and conformational stiffness of DR1M and (S)-MAP-N azoaromatic chromophoric counits.