Lanthanide triflates-mediated emulsion cationic polymerization of p-alkoxystyrenes in aqueous media

Emulsion cationic polymerization in water Was achieved with rare earth meta l triflates [Ln(OTf)(3); Ln = Yb, Sc, Dy, Sm, Gd, and Nd; OTf = OSO2CF3] th at are well-known as water-tolerant Lewis acids. Even in the presence of a large amount of surfactants such as dodecylammonium halides, sodium laurylb enzenesulfate, and poly(vinyl methyl ether), Ln(OTf)(3) induced cationic po lymerizations of p-methoxystyrene (pMOS) in aqueous media in conjunction wi th the pMOS-HCl adduct (1) at 30 degrees C. In particular, the use of catio nic surfactants such as dodecyltrimethylammonium chloride accelerated the p olymerization and gave polymers of controlled molecular weights and narrowe r molecular weight distributions (MWDs) (M-w/M-n similar to 1.4) than those in the absence of surfactants. The activity of Ln(OTf)(3) reduced with dec reasing the Lewis acidity or the ionic radii of the central metal. The 1/Yb (OTf)(3) system also induced the polymerization of p-tert-butoxystyrene (tB OS) in aqueous media. The homopolymerization of tBOS in water was found to be less controllable than that of pMOS. Random copolymerization of pMOS and tBOS also proceeded in a long-lived fashion in the presence of surfactants . The emulsion cationic polymerization most probably proceeds via the carbo cationic species generated from the dormant C-Cl polymer terminal in the or ganic phase and Ln(OTf)(3) entering from the aqueous phase.