Synthesis and characterization of high T-g organo-soluble side-chain copolyimides containing a triazine-azo chromophore

Two series of copolyimides, OPI(x) and PPI(x), containing a triazine-azo ch romophore were prepared by:a two-step process, which includes a solution po lycondensation followed by a chemical imidization. The copolyimides obtaine d were characterized by FTIR spectroscopy, UV-Vis spectroscopy, DSC and TGA . The obtained copolyimides are soluble in aprotic organic solvents such as N-methyl-2-pyrrolidone (NMP), N, N-dimethyl acetamide (DMAc), N, N-dimethy l formamide (DMF), dimethylsulfone (DMSO) and 1,4-butyrolactone. They are a lmost completely transparent at wavelengths greater than 500 nm, The intrin sic viscosities of OPI(x) and PPI(x) are in the range 0.25-0.50 dL/g. All c opolyimides possess high Tg and thermal stability. T(g)s are about 573 K fo r copolyimides based on pyromellitic dianhydride(PMDA) and 533-543 K for th ose based on 3,3',4,4'-diphenylethertetracarboxylic dianhydride(OPDA) and a re almost independent of the chromophore loading level. The 5% weight loss temperatures of the copolyimides are more than 100 K higher than the corres ponding T(g)s and this high thermal stability would ensure high-temperature poling of the copolyimides.