Synthesis and characterization of main chain degradable poly(amide-imide)s with acetal unit

A series of main chain degradable poly(amide-imide)s 7 were prepared from acetal-containing diimide-dicarboxylic acid 5 with various aromatic diamine monomers 6 by the direct polycondensation in NMP using triphenyl phosphite/pyridine as condensing agents. The novel diimide-dicarboxylic acid 5 bearing 2-trifluoromethylphenyl substituted acetal unit was synthesized by the condensation reaction of amine compound 4 with trimellitic anhydride. All the polymers were obtained in quantitative yields with inherent viscosities of 0.41-0.53 dl g(-1). The structure of polymers was confirmed by IR, H-1 NMR and C-13 NMR spectroscopy. The poly(amide-imide)s obtained were soluble in polar solvents such as NMP and DMAc. Most were cast into transparent and flexible films, which had tensile strengths ranging from 40 to 80 MPa, elongation-to-breakage from 2.8 to 6.6%, and initial moduli from 1.2 to 1.6 GPa. The glass transition temperatures of these polymers were in the range 208-232degreesC and showed 5% weight loss temperature ranging from 350 to 385degreesC under air or nitrogen atmosphere. Furthermore, the acid-catalyzed degradation behavior of poly(amide-imide)s 7 was also investigated.