Preparation of complex multiblock copolymers via aqueous RAFT polymerization at room temperature

Abstract

We describe a simple new approach towards complex multiblock copolymer architectures at ambient temperatures. Using the redox pair TBHP/AsAc for initiation, aqueous reversible addition-fragmentation chain transfer (RAFT) polymerization is used to develop a one-pot sequential monomer addition process that yields high order multiblock copolymers at 25 °C. Working at ambient temperature permits the polymerization of monomers yielding polymers with lower critical solution temperature (LCST) and reduces the risk of side reactions by chain transfer. Our approach is initially demonstrated with the preparation of well-defined low and high degree of polymerization (DP) poly(4-acryloylmorpholine) (PNAM) and poly(2-hydroxyethyl acrylate) (PHEA) multiblock homopolymers with Đ under 1.35. To highlight the potential of our approach, more challenging multiblock copolymers were prepared: a pentablock copolymer of high DP (an average of 100 per block) including low LCST blocks of poly(N-isopropylacrylamide) (PNIPAM) and poly(N,N-diethylacrylamide) (PDEA), two polyacrylate multiblock copolymers (DP of 10 per block) using a range of different functional acrylate monomers, and a heptablock copolymer (DP 10 per block) consisting of both polyacrylate and polyacrylamido blocks, all with a final dispersity of around 1.3.