Synthesis of a novel difunctional NLO azo-dye chromophore and characterizations of crosslinkable copolymers with stable electrooptic properties

摘要

The synthesis and the nonlinear optical (NLO) properties of crosslinkable copolymers based on a novel NLO azo-dye chromophore bearing two functions: one used the free-radical copolymerization, that is, the methacrylate group, and the other one used for the crosslinking process, that is, the carboxylic acid function, are described. Copolymerization of this new monomer with glycidyl methacrylate leads to novel soluble crosslinkable NLO copolymers bearing free epoxy and carboxylic groups. The poling process, before crosslinking, is achieved at a temperature (Tp) close to the glass transition temperature, Tg (<70 °C), of the copolymers. At this temperature, no reaction takes place between epoxy and carboxylic acid functions. In fact, crosslinking begins to start at a higher temperature, Tc (Tc very much greater than Tp approximately equals Tg). After the optimization of the poling and crosslinking processes, the NLO crosslinked polymer with 30 mol % of the chromophore exhibits a Tg of 157 °C and a high quadratic susceptibility (d33) of 30 pm/V at 1320 nm. This coefficient is stable at 85 °C for several weeks.