Acid-triggered radical polymerization of vinyl monomers

Reversible addition–fragmentation chain-transfer (RAFT) polymerization is one of the most versatile and robust controlled radical polymerization methods owing to its broad material scope and high tolerance to various functionalities and impurities. However, to operate RAFT polymerization, a constant supply of radicals is required, typically via exogenous thermal radical initiators that are not only challenging to transport and store, but also primarily responsible for termination and end-group heterogeneity. Here we present an acid-triggered RAFT polymerization that operates in the dark and without any conventional radical initiator. Abundant acids (for example, sulfuric acid) are shown to have a dual role initiating and accelerating the polymerization. The polymers prepared have low dispersity and high end-group fidelity. The method is compatible with a wide range of vinyl monomers and solvents, and can be applied to the synthesis of well-controlled high molecular weight block copolymers, as well as to free radical polymerization.