Hydrogen peroxide as initiator in vinyl polymerization in homogeneous system. I. Kinetic studies

Abstract

The kinetic study of the polymerization of methyl methacrylate initiated by hydrogen peroxide in toluene, ethyl acetate, and methyl ethyl ketone as well as in bulk has been made. It has been established that the catalyst has no inhibition period and follows the square root relation. The initiation order is unimolecular with respect to the monomer in the fist two solvents and is half-molecular with respect to methyl ethyl ketone. The value of Δ(= k^t_½/k_p) for methyl methacrylate at 60°C. at various concentrations in the three solvents has been measured and found to remain sensibly constant and its value is 8.43. From bulk polymerization data the value of Δ at temperatures of 50, 60, 80, and 115°C. has been determined and they are 11.62, 8.43, 5.26, and 2.48, respectively. The temperature variation of Δ, and hence the corresponding energy of activation (E_p -½E_t), has also been measured and its value is found to be 5.71 kcals. The initiation constant under a variety of conditions has been determined by two independent methods (kinetic and DP) which have been found to yield values in fairly good agreement with each other, leading to a strong support to the usually assumed mechanism of polymerization. However, the initiation constant is found to change considerably with monomer concentration and change of solvent.