Synthesis,characterization and properties of TAP‐6FDA hyperbranched polyimides with different branching degrees

A series of hyperbranched polyimides were successfully synthesized by condensation polymerization of A₂‐type dianhydride monomer 2,2‐bis(3,4‐dicarboxylphenyl) hexafluoropropane dianhydride (6FDA) and B′B₂‐type triamine monomer 2,4,6‐triaminopyrimidine (TAP). Polymers with different branching degrees (DB) and terminated groups were obtained by changing the monomer addition order and the monomer molar ratio. Fourier transform infrared spectroscopy and ¹H NMR were used to verify the structure of the prepared polyimides, which indicated that the amino group still existed in all the products. The DB of the polymers indicated by ¹H NMR increased from 30% to 79% with the molar ratio of TAP:6FDA decreasing from 1:1 to 1:2. The absolute molecular weights were measured by size‐exclusion chromatography with multi‐angle laser light‐scattering detection, which suggested that the highest molecular weight would be obtained when the molar ratio of amino groups:anhydride groups of the monomers was 3:3.2. With the DB increasing, the d‐spacing values indicated by wide angle X‐ray diffraction increased from 5.15 Å to 5.68 Å and the UV ? visible spectra of the polymers exhibited decreasing cut‐off wavelengths. The 5% weight loss temperature in nitrogen increased with decreasing content of TAP monomer, and the glass transition temperatures of the obtained polyimides decreased from 282 °C to 258 °C with increasing DB. © 2013 Society of Chemical Industry