SYNTHESIS AND INVESTIGATION OF M,M'-DIMETHOXYBENZYL ESTERS AS NOVEL ORGANIC SOLUBLE CATIONIC PHOTOINITIATORS

The cationic homopolymerizations of N-vinylcarbazole 1-methoxy-1,3-but adiene, isobutyl vinyl ether, p-methoxystyrene, and cyclohexene oxide using three m,m'-dimethoxybenzyl esters as initiators have been invest igated under both photochemical and dark conditions. The comparison be tween the thermal polymerization and photopolymerization rates reveale d that these initiators work mainly via a photocationic initiating mec hanism. Only N-vinylcarbazole produced high molecular weight polymer; the other monomers produced only low molecular weight polymers (10(2)- 10(3)). The order of the reactivity of these initiators is m,m'-dimeth oxybenzyl 2,4,6-triisopropylbenzenesulfonate (DMB-TIBS) > m,m'-dimetho xybenzyl m-nitrobenzenesulfonate (DMB-NBS) > m,m'-dimethoxybenzyl tosy late (DMB-T). Changing initiator concentration and reaction temperatur e affected the polymerization yield but had little influence on the po lymer molecular weight. Increasing the monomer nucleophilicity and the stability of the formed counterions enhanced the polymerization rate and raised the product molecular weight. A photochemical initiation me chanism was suggested for these systems.