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

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 (A(2)) at the different feed molar ratio. Monitoring by H-1 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 AB(2)-type amic acid (B'A(2) intermediates) can be formed rapidly in situ when the polymerization is processed at 20 degrees 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 AB(2)-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 'A(2)+B'B-2' based on the principle of unequal reactivity of functional groups. (C) 2017 Elsevier Ltd. All rights reserved.