Light-mediated one-pot synthesis of an ABC triblock copolymer in aqueous solution via RAFT and the effect of pH on copolymer self-assembly

A diblock copolymer showing pH-dependent water solubility is chain extended with a hydrophobic third block to obtain an ABC type amphiphilic triblock copolymer of poly(ethylene oxide-b-(2-dimethylamino) ethyl methacrylate-b-(2-hydroxypropyl methacrylate)). The block copolymer synthesis was carried out by utilizing visible light-mediated RAFT aqueous dispersion polymerization. The block copolymer showed PISA-based self-assembly under acidic conditions when the hydrophobic end block is sufficiently chain extended. The morphology of the self-assembled nanostructures depended on the chain length of the hydrophobic block and the concentration of the reaction solution. As this block copolymer consisted of a pH-sensitive middle unit, the re-assembly of the nanostructures leading to the change in the morphology can be brought about by a simple change in the pH of the solution. The change in pH not only triggered the change in the morphology but also caused the change in the surface roughness of the self-assembled structures.