Synthesis and characterization of new soluble and thermally stable aromatic poly(amide-imide)s based on N-[3,5-bis(N-trimellitoyl)phenyl]phthalimide

A new dicarboxylic acid, N-[3,5-bis(N-trimellitoyl)phenyl]phthalimide (I a), bearing three preformed imide rings was synthesized from the condensation of N-(3,5-diaminophenyl)phthalimide and trimellitic anhydride in glacial acetic acid at 1:2 molar ratio. For study of structure-properties relationship 1,3-bis(N-trimellitoyl)benzene (1b, as a reference) was also synthesized in a similar manner. I a and 1b were characterized by spectroscopic methods and elemental analyses. A series of wholly aromatic poly(amide-imide)s with inherent viscosities of 0.63-1.09 dlg(-1) was prepared by triphenyl phosphite-activated polycondensation from the triimide-dicarboxylic acid la and the reference monomer 1b with various aromatic diamines. All of the polymers were fully characterized by FT-IR and H-1 NMR spectroscopy. The effects of the phthalimide pendent group on the polymers properties such as solubility, crystallinity, and thermal stability were investigated by comparison of the polymers. The polymers obtained from triimide-dicarboxylic acid la exhibited excellent solubility in a variety of solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethylsulfoxide. These poly(amide-imide)s possessed glass-transition temperatures from 334 to 403 degreesC and exhibited excellent thermal stabilities and had 10% weight losses from 541 to 568 degreesC under a nitrogen atmosphere. Poly(amide-imide)s containing phthalimide pendent groups showed higher solubility, higher T-g and T-d10% values than those having no phthalimide pendent groups. (C) 2004 Elsevier Ltd. All rights reserved.