Living radical polymerization of methyl methacrylate with a rhodium(III) complex-organic halide system in dimethyl sulfoxide

Abstract

The polymerization of methyl methacrylate (MMA) with the rhodium(III) complex dihydrido(1,3-diphenyltriazenido)bis(triphenylphosphine)rhodium(III) [RhH2(Ph2N3)(PPh3)2] as a catalyst and an organic halide (CCl4, BrCCl3, or CBr4) as an initiator in dimethyl sulfoxide (DMSO) was studied. For the CCl4 initiator system, a kinetic study of MMA polymerization indicated that polymerization follows first-order kinetics with respect to the monomer and that the number-average molecular weight (Mn) of the polymers produced increases in direct proportion to the monomer conversion. Monomer-addition experiments showed that after addition of further MMA, the Mn of the polymers continues to increase in direct proportion to the monomer conversion. These results confirmed that the polymerization of MMA in the CCl4-initiated system proceeds in a living radical manner. In contrast, the systems involving the bromo compounds BrCCl3 or CBr4 did not show such a living radical nature. For all these initiator systems, the polymers produced had broad molecular-weight distributions. The catalytic activities are discussed in relation to the reaction product between RhH2(Ph2N3)(PPh 3)2 and DMSO.