Kinetics of the polymerization of methyl methacrylate initiated by butylmagnesium bromides and dibutylmagnesium in tetrahydrofuran + toluene

Abstract

The rates, v_p, and degrees of polymerization, DP_n, are governed by relationships different from those of a typical anionic polymerization (e.g. those initiated by organic compounds of the alkali metals). At low temperatures (⩽ 230 K) termination of macrochains is insignificant.

At fractional conversions α⩽ 0.25: DP_n= constant α/[BuⁿMgBr]₀, and at α⩽ 0.4: v_p=–d[MMA]/dt=v_p0=k[Bu_nMgBr]₀[MMA]₀ where the subscript 0 implies an initial rate or concentration. The kinetics of polymerization when either Buⁿ₂Mg or Bu^sMgBr is used are similar.

These relationships can be explained on the assumption that the rate and efficiency of initiation are governed by the reactions of an initiator-monomer complex and that the propagation reaction proceeds through a complex between monomer and the propagating chain-end.