Kinetics of polymerization of 2-hydroxyethylmethacrylate initiated by a titanium(iii)-dimethylglyoxime redox system

The polymerization of 2-hydroxyethylmethacrylate (HEMA) initiated by the redox system titanium(III)-dimethyl glyoxime (DMG) was studied in dimethyl formamide (DMF)-water (80:20 v/v) medium in the temperature range 290-310 K. The rate of polymerization (R_p) was investigated at various concentrations of reductant, oxidant, sulfuric acid, and monomer. Cyclic voltametric sensing of dimethylglyoxime under the kinetic conditions demonstrated its reduction behavior. From the obtained results, it was inferred that the polymerization reaction was initiated by an organic free radical arising from the titanium(III)-dimethylglyoxime redox system. Chain termination of the polymer took place predominantly by mutual coupling and small fraction by chain transfer mechanism involving solvent molecules. The effects of some water miscible organic solvents and surfactants on the rate of polymerization were investigated. The temperature dependence of the rate was studied and the activation parameters were computed using Arrhenius and Eyring plots. A suitable kinetic scheme is proposed on the basis of experimental observations.