Study on side-chain second-order nonlinear optical polyimides based on novel chromophore-containing diamines. I. Synthesis and characterization

Side-chain second-order nonlinear optical polyimides were prepared from fou r novel chromophore-containing diamines and 4,4'-(hexafluoroisopropylidene) diphthalic anhydride by a traditional two-step process that included a sol ution polycondensation followed by a chemical imidization. The four diamine s were 2,4-di-beta-aminoethylamino-6-p-nitrophenylamino-1,3,5-triazine (M1) , 4-nitro-4'-[N-(4,6-di-beta-aminoethylamino)-1,3,5-triazin-2-yl]amino azob enzene (M2), 2,4-di-p-aminophenylamino-6-p-nitrophenylamino-1,3,5-triazine (M3), and 4-nitro-4'-[N-(4,6-di-4-aminophenylamino)-1,3,5-triazin-2-yl]amin o azobenzene (M4). All the polyimides exhibited maximum ultraviolet-visible absorption peaks or shoulders of chromophores at wavelengths below 400 nm, and those based on M1 and M3 were transparent at wavelengths above 450 nm, whereas those based on M2 and M4 were transparent at wavelengths above 550 nm. The polyimides possessed high glass-transition temperatures (T-g's; 21 8-247 degrees C) and thermal decomposition temperatures. They were soluble in aprotic solvents such as N-methyl-2-pyrrolidone, N,N-dimethyl acetamide, N,N-dimethyl formamide, and dimethylsulfone. Some were even soluble in com mon low-boiling-point solvents such as tetrahydrofuran. (C) 1999 John Wiley & Sons, Inc.