CELLOBIOSE CE(IV) AS A REDOX INITIATING SYSTEM FOR AQUEOUS POLYMERIZATION OF METHYL-METHACRYLATE

Polymerization of methyl methacrylate initiated by ceric ammonium nitrate-cellobiose has been investigated in aqueous nitric acid in the temperature range 20.5-35°. Conversion attained a maximum value and ceric ion consumption was found to be complete. The reaction orders depended on ceric ion concentration. At moderately high Ce(IV) concentration (1 × 10-3 M), the orders were 0.5 and 1.5 with respect to cellobiose and monomer respectively; at low Ce(IV) concentration (3.5 × 10-4 M), these orders changed to 1 and 0.5, respectively. The rate of ceric ion disappearance was directly proportional to Ce(IV) concentration and the inverse of the rate was proportional to the inverse of the cellobiose concentration. Both rates increased with rise in temperature. The average-molecular weight can be controlled by variations in cellobiose, Ce(IV) and monomer concentrations, as well as in temperature. A kinetic scheme involving oxidation of cellobiose by Ce(IV) via complex formation, decomposition of the complex giving the initiating free radicals, initiation, propagation, mutual termination of the polymer chains, and an oxidative termination of primary radicals by Ce(IV) is proposed. © 1990.