Metal triflates and tetrafluoroborates as water-tolerant Lewis acids for cationic polymerization in aqueous media

Metal triflates or tetrafluoroborates, such as Zn(OTf)(2), Cu(OTf)(2), Sn(O Tf)(2), and Zn(BF4)(2) (OTf = -OSO2CF3), were employed as water-tolerant Le wis acids for the emulsion cationic polymerization of p-methoxystyrene (pMO S) in heterogeneous aqueous media. All these metal compounds, in addition t o rare earth metal triflates such as Yb(OTf)a already reported by us, induc ed the polymerization of pMOS in conjunction with the pMOS-HCl adduct (1) ( initiator) and dodecyltrimethylammonium chloride (surfactant) at 30 degrees C in water. The pMOS polymerization was controlled, where the molecular we ights of the polymer increased with monomer conversion;and the molecular we ight distributions were relatively narrow (M-w/M-n similar to 1.4). H-1 NMR analysis of the obtained polymers showed that the chlorine atom originatin g from 1 was attached to the growing polymer terminal. In addition, the wat er tolerance of these catalysts was confirmed by F-19 NMR analysis. Thus, t he emulsion cationic polymerization proceeds via reversible activation of t he C-Cl terminal mediated by the water-tolerant Lewis acid, which enters fr om the aqueous phase into the organic phase.