Controlling polymer molecular weight distributions by light through reversible addition‐fragmentation chain transfer‐hetero‐Diels–Alder click conjugation

Abstract Light‐regulated polymerization has emerged as a powerful tool to control the process of polymerization. However, tuning the polymer molecular weight distribution (MWD) by light is still not well developed. Here, we present a convenient approach for controlling the MWD in reversible addition‐fragmentation chain transfer (RAFT) polymerization by exploiting an ultraviolet light‐induced RAFT‐hetero‐Diels – Alder (RAFT‐HDA) reaction with a photoenol diene. The key point in this strategy is to terminate part of the propagating chains at a specific time by the RAFT‐HDA reaction. In addition, a photoenol diene with a hydroxyl group is also synthesized and successfully applied to realize this strategy, which can be further utilized for chain extension of ɛ ‐caprolactone ( ɛ ‐CL) by ring opening polymerization to prepare diblock copolymers with different MWDs.