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

The synthesis and the nonlinear optical (NLO) properties of crosslinkable c opolymers based on a novel NLO ate-dye chromophore bearing two functions: o ne used the free-radical copolymerization, that is, the methacrylate group, and the other one used for the crosslinking process, that is, the carboxyl ic acid function, are described. Copolymerization of this new monomer with glycidyl methacrylate leads to novel soluble crosslinkable NLO copolymers b earing free epoxy and carboxylic groups. The poling process, before crossli nking, is achieved at a temperature (T-p) close to the glass transition tem perature,T-g (<70 degrees C), of the copolymers. At this temperature, no re action takes place between epoxy and carboxylic acid functions. In fact, cr osslinking begins to start at a higher temperature, T-c (T-c much greater t han T-p approximate to T-g). After the optimization of the poling and cross linking processes, the NLO crosslinked polymer with 30 mol % of the chromop hore exhibits T-g of 157 degrees C and a high quadratic susceptibility (d(3 3)) of 30 pm/V at 1320 nm. This coefficient is stable at 85 degrees C for s everal weeks. (C) 1999 John Wiley & Sons, Inc.