Living Radical Polymerization of Para-Substituted Styrenes and Synthesis of Styrene-Based Copolymers with Rhenium and Iron Complex Catalysts

Abstract

Living radical polymerizations of para-substituted styrenes (p-chloro, p-methyl, p-acetoxy, p-acetoxymethyl) were examined with the oxo-complex of rhenium(V) [ReO2I: ReO2I(PPh3)2] and half-metallocene carbonyl complexes of iron(II) [FeCpI: FeCpI(CO)2] and iron(I) [Fe2Cp2: Fe2Cp2(CO)4] (Cp = cyclopentadienyl), all coupled with an iodoester initiator [(CH3)2C(CO2Et)I] in the presence of metal alkoxides. Living polymers with narrow molecular weight distributions (MWDs) were obtained from p-chlorostyrene (p-ClSt) with ReO2I and FeCpI (M̄w/M̄n = 1.29 and 1.09, respectively). ReO2I proved effective also for the living polymerization of p-methylstyrene (p-MeSt), while FeCpI failed, probably due to the β-H elimination from the ω-end. In the absence of metal alkoxides, Fe2Cp2 led to living polymerization of p-acetoxystyrene (p-AcOSt) with narrow MWDs (M̄w/M̄n ∼ 1.2) and gave long-lived poly[p-(acetoxymethyl)styrene]. p-MeSt− and p-AcOSt−styrene block copolymers were synthesized by sequential polymerizations with ReO2I and Fe2Cp2, respectively. The recovered polystyrene with an iodine ω-end (prepared with ReO2I) efficiently initiated the living polymerization of methyl acrylate in the presence of RuCl2(PPh3)3 to give block copolymers.

Keywords

Affiliated Institutions

• Kyoto University JP

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