ADDITION-FRAGMENTATION TYPE INITIATION OF CATIONIC POLYMERIZATION USING ALLYLOXY-PYRIDINIUM SALTS

Allyloxy-pyridinium salts with various substituents on the allylic moi ety are shown to be very efficient coinitiators in radical promoted ca tionic polymerization of cyclohexene oxide. Depending upon the radical initiator chosen, cationic polymerizations may be initiated by either heat or light. For the most part, the mechanism of initiation involve s the addition of free radicals formed by the radical initiator, and a subsequent fragmentation of the energy-rich intermediate yielding ini tiating pyridinium type radical cations. In addition-fragmentation pol ymerization, the substituent at the allylic moiety does not significan tly influence the polymerization rate, thus implying that fragmentatio n is the rate determining step. In some cases, oxidation of the primar ily formed free radicals contributes to the formation of initiating sp ecies. The salts under investigation are also able, to various extents , to initiate cationic polymerization upon external stimulation (heati ng or UV irradiation) without added radical initiators. (C) 1998 Socie ty of Chemical Industry