CO2-Responsive graft copolymers: synthesis and characterization

Abstract

A facile and versatile approach for preparing CO₂-responsive graft copolymers via a grafting-to strategy that combines controlled radical polymerization with post-polymerization modification has been demonstrated. A well-defined poly(N,N-dimethylacrylamide-co-pentafluorophenyl acrylate) (P(DMA-co-PFPA)) was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization bearing reactive pentafluorophenyl esters as grafting sites on a hydrophilic backbone. Then, amino end-functionalized poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) known for its CO₂ responsiveness and hydrophobic poly(methyl methacrylate) (PMMA) were prepared via atom transfer radical polymerization (ATRP) as side blocks, respectively. Subsequently, post-polymerization modification via active-ester amine chemistry, resulted in CO₂-responsive graft copolymers with either homo-side chains or discrete multi-functional hetero side chains. Importantly, this grafting-to strategy utilizing active-ester amine chemistry appeared to be a facile and efficient method to fabricate graft copolymers. Interestingly, both prepared CO₂-responsive graft copolymers – due to their amphiphilic nature – could self-assemble into vesicles in aqueous solution and displayed CO₂-responsive expansion owing to the protonation of tertiary amine groups of PDEAEMA side chains under CO₂ stimulation.