Light-Driven Living/ControlledRadical Polymerizationof Hydrophobic Monomers Catalyzed by Ruthenium(II) Metalacycles.

A versatile photoactivated catalytic system based ona cyclometalatedruthenium(II) complex, composed of strongly coordinating bidentateand relatively labile ligands, in conjunction with a traditional alkylbromide initiator, has been developed for living/controlled radicalpolymerization. Polymerizations of three typical hydrophobic monomersmethylmethacrylate (MMA), styrene (St), and n-butyl acrylate(BA)proceeded to high conversions under visible light irradiation.The polymerization process was photoresponsive, i.e., took place onlyunder irradiation and immediately stopped when the light was turnedoff. Block copolymers of MMA with St and BA with St, as well as statisticalcopolymer of BA and St, could also be conveniently prepared. 1H NMR and electrochemical studies suggest a mechanism of thecatalytic activation, which involves a photoinduced formation of thesolvento 18-electron species cis-[Ru(o-C6H4-2-py)(phen)(MeCN)(acetone)]+through the intermediacy of the 16-electron five-coordinated complex cis-[Ru(o-C6H4-2-py)(phen)(MeCN)]+which is believed to be a crucial intermediate of the overallATRPprocess. [ABSTRACT FROM AUTHOR]