New Insights into the Cationic Polymerization in Emulsion Catalyzed by Water-Dispersible Lewis Acid Surfactant Complexes: A Case Study with p-Methoxystyrene

The process of cationic polymerization of p-methoxystyrene in emulsion using recently discovered water dispersible Lewis acid surfactant complexes (LASCs) has been investigated in detail. These latter are prepared from specific branched sodium dodecylbenzenesulfonate and different metal salts (namely ytterbium, scandium, and indium). First, the reaction rate increases while changing the nature of Yb salt in the range Yb(OTf)(3) > YbEr3 > YbCl3 > Yb(NO3)(3). The nature of metal was also shown to influence the propagation rate, with a fair acceleration of the polymerization when using indium or scandium ions. Raising the temperature led also to an increase of the reaction rate, but the molar mass of obtained polymers decreased. It was also demonstrated that the use of an appropriate initiator (pentachlorophenol) allows controlling to some extent the molar mass of synthesized polymers. Polymer characterization by H-1 NMR spectroscopy revealed a significant fraction of olefinic end groups, indicating that the main chain-breaking process is via chain transfer reactions. All these results are consistent with a mechanism where polymerization proceeds inside the monomer droplets.