A new photoinitiating system for living cationic polymerization of vinyl ethers is reported. In the current approach, visible-light irradiation of dimanganese decacarbonyl (Mn (CO) ) in the presence of an alkyl bromide results in the formation of carbon-centered radicals. The photochemically generated radicals were then oxidized by diphenyliodonium ions to the corresponding cations. These cations can add vinyl ether monomers, which are then rapidly deactivated by the bromide anions to give α-halide functional end groups. Poly(vinyl ether) chains are then grown through successive photoinduced radical oxidation/addition/deactivation (PROAD) in a controlled manner. The living nature of the system is evaluated through kinetics studies and block copolymer formation.

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A new photoinitiating system for living cationic polymerization of vinyl ethers is reported. In the current approach, visible-light irradiation of dimanganese decacarbonyl (Mn 2 (CO) 10 ) in the presence of an alkyl bromide results in the formation of carbon-centered radicals. The photochemically generated radicals were then oxidized by diphenyliodonium ions to the corresponding cations. These cations can add vinyl ether monomers, which are then rapidly deactivated by the bromide anions to give a-halide functional end groups. Poly(vinyl ether) chains are then grown through successive photoinduced radical oxidation/addition/deactivation (PROAD) in a controlled manner. The living nature of the system is evaluated through kinetics studies and block copolymer formation.Sincethediscoveryofclassicallivinganionicpolymerization sixty years ago, [1] living polymerizations have been a powerful tool for synthetic polymer chemistry, providing control over molecular weight and functionality, and also facilitating the design and synthesis of complex macromolecular architectures such as block, graft, [2] star, [3] and telechelic polymers. [4] In recent years, there has been tremendous interest in developing new controlled/living polymerization (CLP) methods, involving almost all modes of polymerization processes. Most successful approaches to CLP have emerged from the radical mode, and several CLPs, namely atomtransfer radical polymerization (ATRP), [5] nitroxide-mediated radical polymerization (NMRP), [6] and radical additionfragmentation transfer (RAFT) polymerization, [7] have witnessed remarkable developments. More recently, interest has been directed towards photoinduced processes that allow not only control over the polymerization, but also spatial and temporal control. Most of these approaches are based on photoinduced electron-transfer reactions. Various photoactive compounds, such as photoinitiators, [8] dyes, [9] mesoporous structures, [10] and nanoparticles, [11] have been successfully employed the electron transfer and reduction of Cu II to Cu I , which in turn catalyzes the ATRP process. A similar photoinduced redox strategy has been applied to azide-alkyne click reactions, which also utilize Cu I species. [12] Photoinduced electron-transfer-promoted ATRP has also been reported for Ir(ppy) 3 -based systems by Hawker and co-workers. [13] The Boyer group has also elegantly extended this concept to RAFT process. [14] It was recently demonstrated that the photoinduced ATRP method can also be applied in completely organic systems by using phenothiazines [15] and dyes [16] as photoreductants. Mechanistic details evaluated by experimental and computational studies using several phenothiazine derivatives revealed that control of the polymerization is strongly related to the structure of the phenothiazine compounds. The promising field of photoiniated controlled polymerization is further extended by the ring-opening metathesis polymerization reported by Boydston et al. [17] Although photoinitiated cationic polymerization ...

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