Factors affecting bottlebrush polymer synthesis by the transfer-to method using reversible addition-fragmentation chain transfer (RAFT) polymerization

The transfer-to method is a unique way to prepare bottlebrush polymers by reversible addition-fragmentation chain transfer (RAFT) polymerization. This little-studied bottlebrush polymer synthesis strategy is distinct from the grafting-from, grafting-to, and grafting-through strategies and therefore may have specific advantages over these other synthetic approaches. Herein, we study the factors affecting the composition of bottlebrush polymer samples prepared by RAFT transfer-to, with particular emphasis on bottlebrush polymer molecular weight (MW) and dispersity (D) and the percentage of "dead" linear polymer as a function of initiator concentration, [M]/[CTA] ratio, backbone length, and monomer type. The lowest quantities of dead polymer were obtained under conditions that limited the MW of the bottlebrush polymer side-chains and that discouraged termination reactions. Under optimized conditions, high MW bottlebrush polymers were prepared with low dispersities and few dead polymer impurities.