Tying Up loose ends: some mechanistic aspects of catalytic chain transfer

Polymn. of Me methacrylate in the presence of two catalytic chain transfer agents was studied and several factors were examd. in terms of effects on the chain transfer process. The chain transfer process was highly intolerant of initiator impurities, but was able to endure a large excess of oxygen. The temp. dependency of the chain transfer process was detd. for cobaloxime boron fluoride (COBF) and cobalt(meso-Ph4-porphyrin) (CoP) catalysts. A study of mol. wt. (MW) or kinetics of the chain transfer (kt) process would be a better gauge of the catalyst activity. Activation energies were detd. at two concns. of initiator; the transfer process has a dependence on initiator concn. A mechanism for this dependency is proposed that involves a redn. in the active catalyst concn., and the measured values for concn. and kt must be apparent values. An addnl. consequence of the initiator dependence is that the MW of the polymer products will be directly dependent on the concn. of the initiator. [on SciFinder (R)]