REDOX POLYMERIZATION OF 2-HYDROXYETHYL METHACRYLATE .2. KINETICS, MECHANISM AND SOLVENT EFFECT USING MANGANESE TRIACETATE CYANOACETIC ACID AS THE REDOX SYSTEM

Polymerization of 2-hydroxyethyl methacrylate (HEMA) initiated by the redox system manganese triacetate (Mn(III)/cyanoacetic acid (CAA) was investigated kinetically in DMF and in HOAc/water (80:20 v/v). Monomer (M) conversion was followed gravimetrically. Polymerization was carri ed out at 31 degrees C and at 41 degrees C. The rate of polymerization R(p) in DMF is expressed by the equation, R(p) alpha [M](1,4) [Mn(III )](0,4) [CAA](0,4). In HOAc/water, the polymerization exhibited a stro ng dependence on the concentration of Mn(III). That is, at low concent rations of Mn(III), the rate variations are [M](1,0), [CAA](0,5) and [ Mn(III)](0,5) while at high Mn(III) concentration the polymerization r ates are independent of [Mn(III)] and vary as a function of [M](1,5) a nd [CAA](0,5). Enhanced oxidation of the primary radicals by Mn(III) a t higher concentrations has been elicited to explain the observed orde rs. The degree of polymerization was found to increase with increase i n concentrations of monomer and decrease in concentrations of CAA and Mn(III). The polymerization rates as well as the molecular weights of the polymers are higher in HOAc/water than in DMF. The enhanced polyme rization rates have been attributed to the increased propagation and t he reduced termination rates.