Here, we exploit the selectivity of photoactivation of thiocarbonylthio compounds to implement two distinct organic and polymer synthetic methodologies: (1) a single unit monomer insertion (SUMI) reaction and (2) selective, controlled radical polymerization via a visible-light-mediated photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) process. In the first method, precise single unit monomer insertion into a dithiobenzoate with a high reaction yield (>97%) is reported using an organic photoredox catalyst, pheophorbide a (PheoA), under red light irradiation (λ_max = 635 nm, 0.4 mW/cm²). The exceptional selectivity of PheoA toward dithiobenzoate was utilized in combination with another catalyst, zinc tetraphenylporphine (ZnTPP), for the preparation of a complex macromolecular architecture. PheoA was first employed to selectively activate a dithiobenzoate, 4-cyanopentanoic acid dithiobenzoate, for the polymerization of a methacrylate backbone under red light irradiation. Subsequently, metalloporphyrin ZnTPP was utilized to selectively activate pendant trithiocarbonate moieties for the polymerization of acrylates under green light (λ_max = 530 nm, 0.6 mW/cm²) to yield well-defined graft co-polymers.

Uniform synthetic polymers with precisely defined molar mass and monomer sequence (primary structure) have many potential high‐value applications. However, a robust and versatile synthetic strategy for these materials remains one of the great challenges in polymer synthesis. Herein we describe proof‐of‐principle experiments for a modular strategy to produce discrete oligomers by a visible‐light‐mediated radical chain process. We utilize the high selectivity provided by photo‐induced electron/energy transfer (PET) activation to develop efficient single unit monomer insertion (SUMI) into reversible addition–fragmentation chain‐transfer (RAFT) agents. A variety of discrete oligomers (single unit species, dimers, and, for the first time, trimers) have been synthesized by sequential SUMI in very high yield under mild reaction conditions. The trimers were used as building blocks for the construction of uniform hexamers and graft copolymers with precisely defined branches.

Visible light regulated ring opening polymerization in the presence of reversible merocyanine-based photoacid is reported in this article.