RAFT without an “R-Group”: From Asymmetric Homo-telechelics to Multiblock Step-Growth and Cyclic Block Copolymers
Karen Hakobyan, Christopher S. P. McErlean, Markus Müllner
Abstract
The amalgamation of photoredox catalysis and reversible-deactivation radical polymerization (RDRP) has offered new avenues of controlling polymer synthesis in recent years. Additionally, the incorporation of bismuth oxide catalysts offers advantages to overcome the limitations of current endogenous catalysis. In this study, we used bismuth oxide to employ dithiocarbonyl disulfides as chain transfer agents (CTAs) in reversible addition–fragmentation chain transfer (RAFT) polymerizations. Despite using CTA precursors with a symmetric molecular structure, we show that the corresponding homo-telechelic (co)polymers propagate with asymmetric growth in one direction only. We employed this methodology to produce homo-telechelic AB diblock copolymers and ABC triblock terpolymers, which after aminolysis can undergo reversible oxidative step-growth polymerization or ring-closure to form either unusual multiblock copolymers or cyclic block copolymers.