| Abstract: | A study of the polymerization of methyl methacrylate initiated by the binary systems of some activated metals and organic halides has been made. It was found that the initiator activities of these systems were greatly dependent on the kind and the preparation or activation method of the metals (i.e., oxidation potential, surface area, and purity), and also on the kind of organic halides (i.e., bond-dissociation energy of their carbon–halogen bonds). From the kinetic studies of the polymerization at 60°C with the system reduced nickel–carbon tetrachloride, the rate of polymerization was found to be proportional to the monomer concentration and to the square root of concentration of both nickel and carbon tetrachloride at the lower concentration range of carbon tetrachloride, indicating that the system induced the radical polymerization. A similar conclusion was also obtained from the copolymerization with styrene with this system at 60°C, i.e., the resulting copolymer composition curve was in agreement with that obtained with azobisisobutyronitrile (AIBN). The apparent overall activation energy for the methyl methacrylate polymerization with this system was estimated to be 7.5 kcal/mole, which was considerably lower than that with AIBN. On the basis of the results obtained, an initiation mechanism for the polymerization with these initiator systems is presented and discussed. |
