Mg. Mikhael et al., SYNTHESIS AND INVESTIGATION OF M,M'-DIMETHOXYBENZYL ESTERS AS NOVEL ORGANIC SOLUBLE CATIONIC PHOTOINITIATORS, Macromolecules, 28(17), 1995, pp. 5951-5954
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.