Tailoring the Morphology of Polymer/Montrnorillonite Hybrid Latexes by Surfactant-Free Emulsion Polymerization Mediated by Arnphipathic MacroRAFT Agents

In this work, we report the reversible addition fragmentation chain transfer (RAFT)-mediated synthesis of polymer/montmorillonite (MMT) hybrid latexes by surfactant-free emulsion polymerization. Macromolecular RAFT (macro-RAFT) agents combining repeating units of acrylic acid (AA), n-butyl acrylate (BA), poly(ethylene glycol) methyl ether acrylate (PEGA), or 2-(dimethylamino)ethyl methacrylate (DMAEMA) were adsorbed on exfoliated sodium MMT platelets and the resulting aqueous colloidal dispersions were used as the reaction medium for emulsion copolymerization of methyl methacrylate and BA under starved-feed conditions. The AA- and PEGA-containing macroRAFT agents led to the formation of polymer-decorated-clay platelets, indicating some affinity of the growing polymer chains for the clay surface, albeit not sufficient for the complete encapsulation of the clay sheets inside the polymer particles. When DMAEMA-based macroRAFT agents were used, transmission electron microscopy analyses of the hybrid latexes revealed the formation of a polymer layer on the MMT platelets indicating that the polymerization took place on the inorganic surface resulting in full encapsulation while preserving the shape anisotropy of the original clay mineral. (AU)