Nickel-Mediated Living Radical Polymerization of Methyl Methacrylate

Abstract

Nickel(II) bis(triphenylphosphine)halides [NiX 2 (PPh 3 ) 2; X = Cl, Br] were employed for possible living radical polymerization of methyl methacrylate (MMA) in conjunction with an organic halide as an initiator [R−X: CCl 4, CCl 3 Br, and (CH 3 ) 2 CBrCO 2 C 2 H 5 ] in the presence of Al(O i Pr) 3 in benzene at 80 °C. The bromide-based initiating system [CCl 3 Br/NiBr 2 (PPh 3 ) 2 ] gave living polymers with narrow molecular weight distributions, whereas the chloride-based system [CCl 4 /NiCl 2 (PPh 3 ) 2 ] led to bimodal molecular weight distributions. The systems involving chloride and bromide [CCl 4 /NiBr 2 (PPh 3 ) 2 and CCl 3 Br/NiCl 2 (PPh 3 ) 2 ] failed to induce living polymerizations. The polymers obtained with (CH 3 ) 2 CBrCO 2 C 2 H 5 /NiBr 2 (PPh 3 ) 2 were also living and possessed one initiator moiety at the α-end per polymer chain, which indicates the polymerization proceeds via the activation of the C−Br terminal by the nickel(II) bromide complex.