Preparation of hyperbranched aromatic polyimide without linear units by end-capping reaction

Direct self-polycondensation of an AB(2) type monomer (1) followed by chemical modification with a branched reagent (2) afforded a precursor. Chemical imidization of the precursor gave a hyperbranched aromatic polyimide (12) with a weight-average molecular weight of 98 000 and an inherent viscosity of 0.13 dL/g. The structures of polymers were successfully characterized by H-1 NMR and IR spectroscopy. Using a model compound, the degree of branching (DB) of the hyperbranched polyimide was determined to be 1.0 by H-1 NMR analysis. A significant difference in T-1 (H-1 NMR pulse spin-lattice relaxation time) values between dendritic, linear, and terminal units was not observed. T-1 values were found to decrease with increasing the size of end groups. By thermal analyses, 5 wt % thermal loss and glass transition temperatures of polyimides were observed at above 365 degreesC and at around 170 degreesC, respectively. The precursor and polyimides exhibited good solubility in NMP, DMF, and THF.