Synthesis and characterization of hyperbranched polyimides from a novel B’B2-type triamine with tert-butyl side group

Abstract

A novel triamine (1) with tert-butyl side group, N1,N1-bis(4-aminophenyl)-4-(tert-butyl)benzene-1,3-diamine, is synthesized and then polymerized with the dianhydride 6FDA (A2) at the different feed molar ratio. Monitoring by 1H NMR spectrum, the reactivity of 3-amino group with ortho-tert-butyl is much lower than that of 4′/4″-amino groups in triamine 1. Thus AB2-type amic acid (B’A2 intermediates) can be formed rapidly in situ when the polymerization is processed at 20 °C and the molar ratio of 1/6FDA is 1:2. Subsequently with increasing the polymerization temperature, 3-amino group with ortho-tert-butyl in AB2-type intermediates is activated and self-polycondensed with anhydride groups to produce hyperbranched polyimide (HBPI) without gelation. This indicates that it’s an effective approach to decrease the reactivity of amino groups in triamine by introducing tert-butyl into its ortho-position and HBPIs can be prepared conveniently through the method of ‘A2+B’B2′ based on the principle of unequal reactivity of functional groups.