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 fro m the condensation of 3,6-diamino-N-methylcarbazole (c) and trimellitic anh ydride. The diamine c was synthesized in three steps starting from the meth ylation of carbazole, followed by nitration and catalytic hydrazine reducti on. A series of N-methylcarbazole-containing poly(amide-imide)s were synthe sized by direct polycondensation from the diimide-diacid I with various aro matic 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, includi ng N-meth-yl-2-pyrrolidone and N,N-dimethylacetamide (DMAc). Transparent, f lexible, and tough films of these polymers could be cast from DMAc solution s, and these films exhibited excellent mechanical strength. The glass-trans ition temperatures of these poly(amide-imide)s were in the range 317-362 de greesC. All the poly (amide-imide) did not degrade noticeably below 480 deg reesC in nitrogen, and the 10% weight loss temperatures and char yields at 800 degreesC were above 520 degreesC and 60% in nitrogen, respectively, ind icating high thermal stability.