Living Radical Polymerization in Water and Alcohols:  Suspension Polymerization of Methyl Methacrylate with RuCl2(PPh3)3 Complex

Water and alcohols were employed as solvents for the living radical polymerization of methyl methacrylate (MMA) with the R−X/RuCl2(PPh3)3 initiating systems in the presence and absence of Al(Oi-Pr)3 at 80 °C (initiator R−X: PhCOCHCl2, CCl3Br). These Ru(II)-based systems indeed led to living suspension polymerization even in such protonic solvents to give polymers with controlled molecular weights and narrow molecular weight distributions (M̄ w/M̄ n = 1.1−1.3). The living polymerizations in water proceeded faster than those in toluene, and additives such as Al(Oi-Pr)3 were not necessarily required for the polymerization to occur. Especially, the PhCOCHCl2/RuCl2(PPh3)3 initiating system gave high molecular weight poly(MMA) (M̄ n ∼ 105) with narrow molecular weight distributions (M̄ w/M̄ n ∼ 1.1) in water even without Al(Oi-Pr)3. Similar Ru(II)-mediated living processes were feasible in such alcohols as methanol, isobutyl alcohol, and tert-amyl alcohol under similar conditions. The success of these living suspension polymerizations in aqueous and alcoholic media attests their radical mechanism as well as the tolerance of the ruthenium complex and the dormant carbon−halogen bond to water and alcohols, where transition-metal complexes are often deactivated.