Preparation of Hyperbranched Aromatic Polyimide without Linear Units by End-Capping Reaction

Direct self-polycondensation of an AB2 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 1H NMR and IR spectroscopy. Using a model compound, the degree of branching (DB) of the hyperbranched polyimide was determined to be 1.0 by 1H NMR analysis. A significant difference in T1 (1H NMR pulse spin−lattice relaxation time) values between dendritic, linear, and terminal units was not observed. T1 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 °C and at around 170 °C, respectively. The precursor and polyimides exhibited good solubility in NMP, DMF, and THF.