Abstract
A new A(A′) + B3 approach to synthesizing hyperbranched polyimides (HBPIs) based on sydnone-maleimide double cycloaddition (SMDC) was investigated. N-phenylsydnone as the latent bifunctional monomer A(A′) exhibited the unique nonequal reactivity in SMDC reaction, and the irreversibly double cycloadduct was the only resultant of SMDC. Therefore, the gelation could be effectively avoided and the degree of branching (DB) was improved. The structures of HBPIs were well characterized by FT-IR, 1H NMR, 13C NMR and GPC. The effects of monomer concentration, feeding modes and molar ratios on the polymerization of HBPIs were investigated. The polymerization based on SMDC could be efficiently proceeded at relative high monomer concentration to afford HBPIs with moderate molecular weight and low polydispersity. Due to the characterics of SMDC, only the HBPIs terminated with maleimde groups could be obtained by the A(A′) + B3 approach, and they could be further modified easily. All the as-synthesized HBPIs exhibited the good solubility and thermal stability.
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