Tying up loose ends: Some mechanistic aspects of catalytic chain transfer

Polymerisation of methyl methacrylate in the presence of two catalytic chai n transfer agents has been investigated. Several factors were examined to s ee how they would affect the chain transfer process. Oxygen and initiator i mpurities added to the system were found to be detrimental. The transfer pr ocess was highly intolerant of initiator impurities, but was able to endure a large excess of oxygen. The temperature dependencies of the chain transf er process were determined for cobaloxime boron fluoride (COBF) and cobalt( meso-Ph-4-porphyrin) (CoP). The results showed that a study of MW, or k(tr) would be a better gauge of the catalyst activity. Activation energies were determined at two concentrations of initiator and it was discovered that t he transfer process has a dependence on the initiator concentration. A mech anism for this dependency is proposed that involves a reduction in the acti ve catalyst concentration. As a result, the measured values for C-tr, and k (tr), must be apparent values. An additional consequence of the initiator d ependence is that the MW of the polymer products will be directly dependent on the concentration of the initiator.