Poly(ethylene glycol)-induced acceleration of free radical polymerization of methyl methacrylate: effects of highly viscous solvent and kinetic study

Abstract

Poly(ethylene glycol) with a molecular weight of 400 (PEG400) as an environmentally benign and highly viscous polymeric solvent was found to effectively accelerate the free radical polymerization (FRP) of methyl methacrylate and to afford a high-molecular-weight polymer. When the polymerization in PEG400 was performed at a monomer concentration of 3.0 mol l−1 and an initiator (2,2′-azobis(isobutyronitrile)) concentration of 0.3 × 10−2 mol l−1, the monomer conversion was completed for 6 h to afford a polymer with a number-average molecular weight (Mn) of 838 000. After polymerization, the PEG400 solvent was readily recovered and reused. The solvent effects of highly viscous PEG400 were kinetically analyzed. The polymerization rate (Rp) was proportional to the monomer concentration and the square root of both the initiator concentration and the viscosity of the polymerization media (η). For the FRP in the mixed solvents of PEG400 and toluene, both Rp and Mn values increased linearly with the square root of the η value. The kinetic study has shown that the highly viscous PEG400 solvent largely suppresses diffusion-controlled bimolecular termination. Poly(ethylene glycol) with a molecular weight of 400 (PEG400) as an environmentally benign and highly viscous polymeric solvent was found to effectively accelerate the free radical polymerization of methyl methacrylate and to afford a high-molecular-weight polymer. The polymerization rate and the polymer molecular weight increase linearly with the square root of the viscosity η of the polymerization media. The kinetic study has shown that the highly viscous PEG400 solvent largely suppresses diffusion-controlled bimolecular termination.