TIRP─Thiol-Induced, Light-Activated Controlled Radical Polymerization

Controlled radical polymerizations (CRPs) are one of the most important ways to obtain uniform, defined molecular weight polymers with complex composition and architecture such as block copolymers. A new controlled and light-initiated radical polymerization is introduced that makes use of thiol initiators and an Ir-photocatalyst. Different reaction parameters are studied for their importance in the controlled characteristics of polymerization, such as low dispersity, control of molecular weights, and straightforward access to block copolymers. The light control furthermore allows for simple switching on and off of the polymerization. We propose a mechanism for the so-called thiol-induced, light-activated, controlled radical polymerization (TIRP), which includes the formation of dormant species and their light- and catalyst-dependent equilibrium with the active polymer chain end. TIRP enriches the portfolio of controlled and light-initiated polymerization methods by its viability at mild conditions and the possibility to grow polymers from a large variety of readily available thiols.