Facile Access to Multistimuli-Responsive Self-Assembled Block Copolymers via a Catechol/Boronic Acid Ligation

A wide range of boronic acid and nitrocatechol end-functionalized homopolymers were prepared via RAFT polymerization from functionalized chain transfer agents (CTAs). Next, the coupling reaction between complementary end-functionalized blocks led to amphiphilic block copolymers (BCPs) featuring a multistimuli-responsive reversible covalent boronate ester junction between both blocks. The efficiency of the coupling reaction, the self-assembly of these BCPs in aqueous medium into nanoaggregates, and their ability to encapsulate hydrophobic molecules were assessed and characterized by NMR (H-1, DOSY), fluorescence spectroscopy, DLS, cryo-TEM, and SEC. The multiresponsiveness of the covalent junction was then investigated upon applying various stimuli such as pH change, addition of sugar, and UV light, resulting in the dissassembly of BCP-based nano-objects and the release of the fluorescent probe. Interestingly, the release profile of model molecules,was found to be readily and finely modulated through the nature of stimuli and also by successively applying different stimuli.