Synthesis and properties of poly(amide-imide)s containing a N-methylcarbazole group

A new dicarboxylic acid monomer containing the N-methylcarbazole and imide structures, 3,6-bis(trimellitimido)-N-methylcarbazole (I), was prepared from the condensation of 3,6-diamino-N-methylcarbazole (c) and trimellitic anhydride. The diamine c was synthesized in three steps starting from the methylation of carbazole, followed by nitration and catalytic hydrazine reduction. A series of N-methylcarbazole-containing poly(amide-imide)s were synthesized by direct polycondensation from the diimide-diacid I with various aromatic diamines. These poly(amide-imide)s had inherent viscosities of 0.66-1.47 dl/g and were readily soluble in a variety of organic solvents, including N-meth-yl-2-pyrrolidone and N,N-dimethylacetamide (DMAc). Transparent, flexible, and tough films of these polymers could be cast from DMAc solutions, and these films exhibited excellent mechanical strength. The glass-transition temperatures of these poly(amide-imide)s were in the range 317-362 degreesC. All the poly (amide-imide) did not degrade noticeably below 480 degreesC in nitrogen, and the 10% weight loss temperatures and char yields at 800 degreesC were above 520 degreesC and 60% in nitrogen, respectively, indicating high thermal stability.