Developing Thiols as a Versatile Organo-Photocatalyst for the Visible-Light-Mediated Polymerization

Thiols are well-established hydrogen atom transfer catalysts for organic reaction development and agents for polymer modification and cross-linking. Herein, we demonstrate a different scenery that aryl thiols like 1-naphthalenethiol and 1-pyrenethiol (PySH) can also act as a photocatalyst for polymerization, which can be photoactivated under visible light to function as a photoacid catalyst to promote the ring-opening polymerization of lactones, affording well-defined polymers with controlled molecular weights and narrowed dispersities (Đ < 1.10). Remarkably, this photoacid could even promote the cationic polymerization of vinyl ether, which usually requires an acid stronger than sulfonic acids. Moreover, PySH can also serve as a photoredox catalyst for the atom transfer radical polymerization (ATRP) of methyl methacrylate. The increased acidity is supported by further investigation of the photophysical and photoacid properties of PySH through combined experimental and theoretical studies.