Synthesis and properties of hyperbranched polyimides from A₂+ B′B₂ monomers and A₂+ B′B₂ + B₂ monomers with various comonomer ratios

A series of hyperbranched polyimides were successfully synthesized by A₂ + B′B₂ approach based on 2,4,6-triaminopyrimidine(TAP) and biphenyl dianhydride(BPDA) . The resulting polyimides were characterized by FTIR, SEC/MALLS, NMP, DSC, TGA. The results showed that BPDA-TAP hyperbranched polyimides had poor thermal stability. In accord with this fact, difunctional B₂ comonoer (4,4′-oxydianiline(ODA))was added into the polymer structure to improve heat resisting property of HBPIs by incorporation. This approach could be described as A₂+ B′B₂ + B₂ or more simply A₂ + B₃ + B₂ copolymerization. Both for the BPDA-TAP-ODA and BPDA-TAP hyperbranched polyimides, the amine-terminated polyimides showed higher glass transition temperature and 10 % weight loss compared with the corresponding anhydride-terminated ones, which can be attributed to the different terminal functional groups and the anhydride residues.