Amphiphilic ABA-Type Block–Graft Molecular Brushes Based on Polyimide

Abstract

New amphiphilic ABA-type molecular brushes of mixed block–graft topology, where the central block B is a molecular brush with a hydrophobic polyimide backbone and hydrophilic side chains of poly(methacrylic acid) and A blocks are peripheral hydrophobic chains of poly(methyl methacrylate), have been synthesized. For the synthesis of the copolymers, an approach based on a combination of atom transfer radical polymerization (ATRP) and click chemistry in the variant of Cu(I)-catalyzed azide–alkyne cycloaddition was proposed. To implement the proposed approach, a procedure was developed for the synthesis of heterofunctional polyimide macroinitiators containing ATRP-initiating groups in each unit and terminal alkynyl groups capable of participating in the “click” reaction. Further, the synthesis of well-defined block–graft ABA molecular brushes was carried out using such initiators. First, peripheral poly(methyl methacrylate) chains were synthesized in a controlled mode using ATRP, followed by their functionalization with azide groups. Then, using the click chemistry approach, these chains were grafted to the terminal alkynyl groups of the heterofunctional initiator. The hydrophilic side chains were introduced into block B using the “grafting from” ATRP method in several steps through the intermediate formation of a regularly grafted prepolymer with poly(tert-butyl methacrylate) side chains. At the last step, as a result of selective acid hydrolysis of the side-chain ester groups in block B, amphiphilic multicomponent brushes with hydrophilic poly(methacrylic acid) units in the side chains were obtained. The possibility of sequential and simultaneous ATRP and click reaction has been examined.