Preparation and properties of thermally stable copolyimides based on novelsecond-order nonlinear-optical chromophore containing diamines

Thermally stable copolyimides were prepared from two novel second-order non linear optical chromophores containing diamines, 4-nitro-4'-[N-(4,6-di-beta -aminoethylamino)- 1,3,5-triazin-2-yl] aminoazobenzene (M1) and 4-nitro-4'- [N-(4,6-di-4-aminophenylamino)-1,3,5-triazin-2-yl] aminoazobenzene (M2); t wo codiamines, 4,4'-diamino-3,3'-dimethyl diphenylmethane (MMDA) and bis-(3 -aminopropyl)-1,1',3,3'-tetramethyldisiloxane (SiDA); and 3,3',4,4'-dipheny l ether tetracarboxylic acid dianhydride (OPDA). All copolyimides possess h igh glass transition temperatures (T-g's) between 237 and 271 degrees C. Co polyimides based on M2 do not exhibit an obvious change in T-g as the M2 co ntent is increased, while those based on M1 show a slight decrease in T-g a s the M1 content is increased. All copolyimides exhibit high thermal decomp osition temperatures. The copolyimides are soluble in aprotic solvents such as NMP, DMAc, DMF, DMSO, and 1,4-butyrolactone. Some are even soluble in c ommon low boiling point solvents such as THF and chloroform. The refractive index of a copolyimide is increased as the chromophore content is increase d, while the birefringence of a copolyimide does not exhibit strong depende nce on the chromophore content. (C) 2000 John Wiley & Sons, Inc.