Facile Chain End Modification of RAFT Polymers

Reversible addition-fragmentation chain transfer (RAFT) polymerization is a widely utilized method to prepare polymers with control over molecular weight and chain end composition. However, there is ongoing effort for the modification of RAFT polymer chain ends due to instability, undesired odors, and potential toxicity. Current methods for chain-end modification include reactions with nucleophiles, thermal elimination, radical cross-coupling reactions, and Diels-Alder reactions. To further contribute to the field, our research involves the modification of RAFT chain ends to bromine in order to make further functionalization easier. In this way, the chain end of RAFT polymers could easily be tailored to fit an array of applications from plastics in materials to micelles for drug delivery. The polymer chain ends are first transformed into thiols by undergoing a known aminolysis reaction. A commercially available brominating reagent is then employed to replace the thiol with a bromine chain end. Optimization is being done on this system by investigating different reagent equivalents, temperatures, solvents, and atmospheres. Currently, the transformation to bromine can be achieved on small molecule systems, but further optimization is needed to modify the chain ends of RAFT polymers.