Synthesis and properties of hydroxylated core-fluorinated diamines and polyurethanes based on them with azobenzene nonlinear optical chromophores in the backbone

We report on the synthesis of core-fluorinated phenylene- and biphenyldianilines, which was accomplished by diazotization reaction of diamines followed by coupling of the obtained diazonium salts with 2-[ethyl(phenyl)amino]-ethanol. Two types of core-fluorinated aromatic units were used in a molecular design of azo-chromophore monomers with enhanced second order nonlinear optical (NLO) properties: octafluorobiphenyl (OFB) and tetrafluorobenzene (TFB) ones. Polymerization of the monomers was performed to obtain polyurethanes with azo-chromophores in the main chain. Comparison of physical and optical properties of these polymers reveals that the main factor influencing the observed NLO activity of the latter is the inherent isomery of the macromolecular chains rather than a variation of the structure of electron-accepting groups.