The visible-light-induced cationic polymerization of isobutylene with a dimanganese decacarbonyl (Mn(CO))/diphenyl iodonium hexafluorophosphate (PhIPF) photoinitiating system in a CHCl/-hexane mixture at -30 °C was reported. It was shown that polymerization is initiated by chloromethylisobutyl carbocations generated by the oxidation of chloromethylisobutyl radicals by PhIPF. The latter are formed via chlorine abstraction from solvent (CHCl) by MnCO· radicals, which are generated by the photoinduced decomposition of Mn(CO), followed by single isobutylene addition. This initiating system allowed us to synthesize valuable low molecular weight polyisobutylene with a relatively low polydispersity ( = 2000-3000 g mol; < 1.7) and high content of -olefin end groups (up to 90%). The molecular weight of polyisobutylenes could be easily controlled in the range from 2000 to 12000 g mol by changing the diphenyl iodonium salt concentration. Poly(β-pinene) with = 5000 g mol and ∼ 2.0 was successfully synthesized using the same photoinitiating system.
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