Optically active thermosensitive amphiphilic polymer brushes based on helical polyacetylene: preparation through “click” onto grafting method and self-assembly

Abstract

Optically active, thermosensitive, and amphiphilic polymer brushes, which consist of helical poly(N-propargylamide) main chains and thermosensitive poly(N-isopropylacrylamide) (PNIPAm) side chains, were prepared via a novel methodology combining catalytic polymerization, atom transfer radical polymerization (ATRP), and click chemistry. Helical poly(N-propargylamide) bearing α-bromoisobutyryl pendent groups was synthesized via catalytic polymerization, followed by substituting the –Br moieties with azido groups. Then, alkynyl terminated PNIPAm formed via ATRP was successfully grafted onto the azido functionalized helical polymer backbones via click chemistry, providing the expected polymer brushes. GPC, FT-IR, and 1H-NMR measurements indicated the successful synthesis of the novel amphiphilic polymer brushes. UV–vis and CD spectra evidently demonstrated the helical structures of the polymer backbones and the considerable optical activity of the final brushes. The polymer brushes self-assembled in aqueous solution forming core/shell structured nanoparticles, which were comprised of optically active cores (helical polyacetylenes) and thermosensitive shells (PNIPAm).