Morphology transitions in RAFT polymerization

Abstract

Polymerization-induced self-assembly and re-organization (PISR) was used to prepare polymeric nanostructured materials with a variety of morphologies. Reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene in a selective solvent, methanol, was carried out using cyanoisopropyl dithiobenzoate-terminated poly(2-dimethylaminoethyl methacrylate) (PDMAEMA-DBT) as the macro chain transfer agent and stabilizer for investigation of the factors influencing the formation of morphologies. Various morphologies, including spherical micelles, nanostrings, vesicles and large compound vesicles, with different shapes were obtained by changing the feed ratios and reaction conditions. The sequential morphologic transitions from spherical micelles to nanostrings, to vesicles and to large compound vesicles via increasing the chain length ratio of the hydrophobic block to the hydrophilic one in the same system were observed for the first time. This approach can be performed at a high concentration, thus it can be scaled up for the reproducible preparation of nanostructured materials in a relatively high volume.