Synthesis of multi-hollow clay-armored latexes by surfactant-free emulsion polymerization of styrene mediated by poly(ethylene oxide)-based macroRAFT/Laponite complexes

Abstract

We report the surfactant-free emulsion polymerization of styrene mediated by a trithiocarbonate poly(ethylene oxide)-based macromolecular RAFT agent (PEO2K-TTC, M_n(PEO) = 2000 g mol⁻¹) in the presence of Laponite clay platelets. Adsorption studies revealed high affinity of the macroRAFT for Laponite. The resulting macroRAFT/clay complexes were used to control the growth of polystyrene chains and generate clay-armored latexes. Undesirable effects observed under the same conditions in the absence of clay, such as rate retardation, a long induction period and loss of colloidal stability, were not observed when the macroRAFT was immobilized on the clay surface. A minimum amount of macroRAFT was necessary to ensure a good control of the polymerization and a narrow molar mass distribution while a too large amount led to similar effects as in the absence of clay due to partitioning of the free non-adsorbing PEO2K-TTC macroRAFT. By a careful selection of the macroRAFT and monomer concentrations, stable multi-hollow clay-armored composite latex particles containing embedded PEO and composed of polymer chains of controlled and narrowly distributed molar masses could be successfully obtained by this technique.