NiBr2(Pn-Bu3)2-mediated living radical polymerization of methacrylates and acrylates and their block or random copolymerizations

Nickel(II) bromide bis(tri-n-butylphosphine) [NiBr2(Pn-Bu-3)(2)] induced living radical polymerization of methyl methacrylate (MMA), methyl acrylate (MA), and n-butyl acrylate (BA) in conjunction with an organic bromide initiator [R-Br: CCl3Br, (CH3)(2)CBrCO2C2H5, and (CH3)(2)CBrCOPh] in the presence of Al(Oi-Pr)(3) additive. In addition, the initiating system with an MMA "dimer" model of the bromine-capped dormant polymer [(CH3)(2)C(CO2CH3)CH2(CH3)CBrCO2CH3] gave living polymers with very narrow MWDs ((M) over bar(w)/(M) over bar(n) similar to 1.1). Similar living polymerizations were possible in the absence of Al(Oi-Pr)(3). NiBr2(Pn-Bu-3)(2) led to faster living polymerizations at a high temperature (120 degrees C; similar to 90% conversion in 2.5 h) or at its high concentration, because it is more thermally stable and more soluble in organic solvents than NiBr2(PPh3)(2). This feature permitted the synthesis of living PMMA of higher molecular weight ((M) over bar(n) 4 x 10(5)) with narrow molecular weight distributions ((M) over bar(w)/(M) over bar(n) = 1.2-1.4). The NiBr2(Pn-Bu-3)(2)-based system was also applicable to Living block polymerizations as well as living random copolymerizations of MMA with MA and BA.