SYNTHESIS, CHIROPTICAL PROPERTIES AND PHOTOINDUCED LINEAR BIREFRINGENCE OF THE HOMOPOLYMER OF (R)-3-METHACRYLOYLOXY-1-(4\u2019-CYANO-4-AZOBENZENE)PYRROLIDINE AND OF THE COPOLYMERS WITH ITS ENANTIOMERIC CO-MONOMER

We have investigated a new optically active photochromic homopolymer poly[(R)-3-methacryloyloxy-1-(40-cyano-4- azobenzene)pyrrolidine] containing in the side-chain a chiral group of one prevailing configuration linked to a transazoaromatic system. As expected it exhibits in solution homogeneous conformations with a prevailing chirality induced by dipole\u2013dipole interactions between side-chain chromophores. Copolymers with the enantiomeric monomer (S)-3- methacryloyloxy-1-(40-cyano-4-azobenzene)pyrrolidine have also been prepared in order to evaluate the effect on the photoinduced optical properties of side-chain chiral groups of opposite configuration in various ratios. The possibility of producing reversible photomodulation of linear birefringence without any significant degradation of these materials seems to be promising for their use in optical data storage

Synthesis, chiroptical properties and photoinduced birefringence of optically active methacrylic copolymers bearing side-chain bisazoaromatic moieties

Three series of optically active photochromic copolymers, deriving from methyl methacrylate (MMA) and the chiral bisazoaromatic monomers (S)-3-methacryloyloxy-1-[4\u2019-phenylazo-(4-azobenzene)]-pyrrolidine [(S)-MPAAP], (S)-3-methacryloyloxy-1-[4\u2019-cyanophenylazo-(4-azobenzene)]-pyrrolidine [(S)-MPAAP-C] and (S)-3-methacryloyloxy-1-[4\u2019-nitrophenylazo-(4-azobenzene)]-pyrrolidine [(S)-MPAAP-N], have been prepared and characterized in solution and in the solid state with the aim to evaluate the effect on their chiroptical and thermal properties originated by the insertion of inactive MMA groups along the main chain. The optical activity displayed by the bisazo polymers is discussed in terms of extent of chiral conformation assumed by the macromolecules as a consequence of dipole-dipole interactions between the bisazoaromatic chromophores. The photoinduction of birefringence has been assessed on thin films of the investigated copolymers in order to evaluate their behaviour as materials for optical data storage. The results are interpreted in terms of copolymer composition and conformational stiffness of the bisazoaromatic chromophoric co-units, which are responsible for the optical response rates, and are compared to those of the similar derivatives containing only one azo bond. The observed enhanced thermal properties and the temporal stability appear of interest for a potential use of these materials in nano technologies for all-optical data manipulation and in optoelectronics