Sulfonic acids as water-soluble initiators for cationic polymerization in aqueous media with Yb(OTf)(3)

Aqueous sulfonic acids (HOSO2R; R = CH3, Ph-p-CH3, and Ph-p-NO2), coupled w ith a water-tolerant Lewis acid, ytterbium triflate [Yb(OM)(3); OTf = -OSO2 CF3], initiate the cationic suspension polymerization of p-methoxystyrene ( pMOS) in heterogeneous aqueous media. They induce controlled polymerization of pMOS at 30 degrees C, and the molecular weights of the polymers (weight -average molecular weight/number-average molecular weight similar to 1.7) i ncrease with conversion. These sus pension polymerizations are initiated by the entry of sulfonic acid from the aqueous phase into the organic phase a nd proceed via reversible activation of the sulfonyl terminus by the Lewis acid. (C) 2000 John Wiley & Sons, Inc.