A highly reducing metal-free photoredox catalyst: design and application in radical dehalogenations

Here we report the use of 10-phenylphenothiazine (PTH) as an inexpensive, highly reducing metal-free photocatalyst for the reduction of carbon-halogen bonds via the trapping of carbon-centered radical intermediates with a mild hydrogen atom donor. Dehalogenations were carried out on various substrates with excellent yields at room temperature in the presence of air

Evolution and future directions of metal-free atom transfer radical polymerization

The increasing impact of atom transfer radical polymerization (ATRP) in fields beyond traditional polymer science has necessitated the development of alternative strategies for controlling polymer growth. Driven by applications that are sensitive to metal ion contamination, "greener" methodologies are emerging as a powerful alternative to conventional ATRP. Organic catalysis represents a major evolution of ATRP with metal-free systems holding significant potential as user-friendly methods for utility in biological and microelectronic applications. In addition, shifting from a combination of thermal activation/metal ions/ligands to simpler organic catalysis/light activation increases compatibility with functional monomers and allows the development of novel surface patterning strategies. Herein, we highlight key discoveries and recent developments in metal-free ATRP, while providing a perspective for future opportunities in this emerging area

Surface‐initiated PET‐RAFT polymerization under metal‐free and ambient conditions using enzyme degassing

An open-to-air method for the efficient synthesis of surface-tethered polymer brushes based on photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization is reported. Key to this approach is an enzyme-assisted strategy using glucose oxidase to facilitate the in situ removal of oxygen during the polymerization process. Control experiments in the absence of glucose oxidase confirm the importance of enzymatic deoxygenation for successful polymerization of a variety of acrylamide, methacrylate, and acrylate monomers. In accordance with controlled polymerization kinetics, a linear increase in brush height as a function of irradiation time for a range of light intensities is demonstrated. Importantly, the use of light to mediate growth and the inherent monomer versatility of PET-RAFT allow for the facile fabrication of well-defined polymer brushes under aqueous conditions. (c) 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 201