Synthesis and properties of hyperbranched aromatic polyamide copolymers from AB and AB(2) monomers by direct polycondensation

Hyperbranched aromatic polyamide copolymers were prepared by direct polycon densation of 3-(4-aminophenoxy)benzoic acid (AB monomer) and 3,5-bis(4-amin ophenoxy)benzoic acid (AB(2) monomer) in the presence of triphenyl phosphit e and pyridine as condensation agents. The structure of resulting polymers was confirmed by IR, H-1, and C-13 NMR measurements. The composition of mon omers determined by H-1 NMR was almost identical to the feed ratio of monom ers. C-13 NMR revealed that the copolymer's were composed of five kinds of repeating units whose ratio was consistent with statistical distribution. T he resulting copolymers were soluble in aprotic polar solvents such as DMF, NMP, and DMSO, and transparent yellow films were prepared from DMF solutio n of the copolymers. The temperature of a 5% weight loss determined by TGA was over 400 degrees C for all copolymers. The feed ratio of the monomers a ffected the glass transition temperatures (T(g)s) and the softening points (T(s)s). A minimum T-g was observed at a 50% of the AB(2) monomer whereas T (g)s gradually decreased with increasing the AB(2) monomer and became const ant over a 60%. Young's modulus determined by the tensile test decreased fr om 2.4 to 1.6 GPa with increasing amount of the AB(2) monomer in the range 0-60%.