Synthesis and characterization of hyperbranched polyimides from A₂+B′B₂ monomers

A series of hyperbranched polyimides with different terminal groups are successfully prepared by changing monomer addition orders and molar ratios using pyromellitic anhydride(PMDA) as A₂ monomers and 2, 4, 6-triaminopyrimidine(TAP) as B′B₂ monomers. The obtained HBPIs' structures and performance are characterized by Fourier transform infrared spectroscopy(FT-IR), proton nuclear magnetic resonance (¹H-NMR), gel permeation chromatography (GPC), thermal gravimetric analysis(TGA), differential scanning calorimetry (DSC), and so on. No gelation happens in the polymerizations probably because of different reactivities of the amino groups at the 2- and 4-/6- positions in TAP. The results show that the degrees of branching (DB) of the polymers and molecular weights increase when the molar ratios of PMDA: TAP increases from 1:1 to 2:1, but glass transition temperature and 10% weight loss decrease.