Abstract: Two series of copolyimides, OPI( x ) and PPI( x ), containing a triazine azo chromophore were prepared by a two step process, which includes a solution polycondensation followed by a chemical imidization.The copolyimides obtained were characterized by FTIRspectroscopy, UV-Vis spectroscopy, DSCand TGA.The obtained copolyimides are soluble in aprotic organic solvents such as N-methyl-2-pyrrolidone(NMP), N,N-dimethyl acetamide(DMAc), N,N-dimethyl formamide(DMF), dimethylsulfone (DMSO) and1,4-butyrolactone.They are almost completely transparent at wavelengths greater than500 nm.The intrinsic viscosities of OPI( x ) and PPI( x ) are in the range0.25-0.50 dL/g.All copolyimides possess high Tg and thermal stability.T_gs are about573 Kfor copolyimides based on pyromellitic dianhydride(PMDA) and533-543 Kfor those based on 3,3′,4,4′ diphenylethertetracarboxylic dianhydride(OPDA) and are almost independent of the chromophore loading level.The5% weight loss temperatures of the copolyimides are more than100 Khigher than the corresponding T_gs and this high thermal stability would ensure high temperature poling of the copolyimides

Key words: Copolyimide, Triazine-azo chromophore, Side-chain, High T_g