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 (A 2 ) at the different feed molar ratio. Monitoring by 1 H 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 °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.