Preparation of auto-photosensitive hyperbranched copolyimide by the condensation of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride with 1,3,5-tris(4-aminophenoxy)benzene through a stage addition reaction method

An approach of stage addition copolymerization was adopted to further improve the organosolubility of the auto-photosensitive hyperbranched polyimide based on TAPOB-BTDA-2,6-dimethylaniline through the incorporation of 6FDA in the inner of macromolecular framework. In the first stage, the amino-terminated hyperbranched oligo(amic acid) was synthesized by the addition of 6FDA solution to TAPOB solution. Next, the oligomer, like a multi-amine monomer with core structure, was added dropwise to the solution of BTDA to give an anhydride-terminated copoly(amic acid), which was then end-capped by 2,6-dimethylaniline. In the end, the precursor was chemically imidized to yield an auto-photosensitive hyperbranched 6FDA-TAPOB-BTDA-2,6-dimethylaniline-based co-polyimide with core-shell structure. The co-polyimide exhibited a great improvement in organosolubility (the solid content of the polymer solution increased from 8 wt% to over 15 wt% in NMP and DMF) compared to the polymer based on TAPOB-BTDA-2,6-dimethylaniline. The two polyimides showed similar thermal properties and photolithographic property, with a patterning resolution higher than 3 mum.