Controlled cationic polymerization of p-methoxystyrene in aqueous media with Yb(OTf)(3)

This study shows that ytterbium triflate [Yb(OTf)(3); OTf = OSO2CF3] induce s cationic polymerizations of isobutyl vinyl ether (IBVE) and p-methoxystyr ene (pMOS) in aqueous media in conjunction with the hydrogen chloride-vinyl monomer adduct [CH3-CHR-Cl; R = OiBu, C6H4-OCH3] as the initiator at room temperature. These "suspension" polymerizations are carried out by adding n eat monomer and then a solution of the initiator into an aqueous solution o f Yb(OTf)(3) under vigorous stirring, and the polymerizations occur smoothl y without being inhibited by water. Under these conditions, IBVE polymeriza tion was uncontrolled, but pMOS can be polymerized in a controlled fashion where the molecular weight distributions (MWDs) are relatively narrow ((M) over bar(w)/(M) over bar(n) similar to 1.4) and the molecular weights incre ase in proportion to monomer conversion. The reactions proved to be cationi c, being quenched by NaOH and EtOH but not by 1,4-benzoquinone. The aqueous hydrochloric acid/Yb(OTf)(3) initiating system also generates similar long -lived pMOS polymer in water. The success in such controlled cationic polym erizations in aqueous media is due to the stability of Yb(OTf)(3) as well a s the dormant C-Cl poly(pMOS) terminal in water.