Solvent effects on the synthesis of poly(methyl methacrylate) by atom-transfer radical polymerization (ATRP)

Abstract

Methyl methacrylate has been polymerized by ATRP at 100°C in bulk, in toluene (50%, v/v) and benzonitrile (50% and 25%, v/v), using methyl 2-halopropionate as initiator (MeXPr, X=Cl or Br), copper halide (CuX) as catalyst and 2,2′-bipyridine (bpy) as ligand. The mixed halogen system MeBrPr/CuCl has also been used. For all initiator systems used, the bulk polymerizations showed linear first-order rate plots, a linear increase of the number-average molecular weight with conversion, and relatively low polydispersities, but low initiator efficiency. The polymerizations performed in toluene do not significantly increase the polymerization efficiency, but the molecular weight distribution is broadened. When the polymerizations are performed in benzonitrile, the polymerization efficiency increases considerably, but is independent of monomer dilution. The molecular weight distributions are narrowed when the polymerizations are performed in 25% (v/v) benzonitrile solution. Experimental number-average molecular weights match the theoretical values when the polymerizations are carried out using the mixed halogen initiator system in benzonitrile solution.