Synthesis and characterization of SiOH-functionalized polymer latexes using methacryloxy propyl trimethoxysilane in emulsion polymerization

Polystyrene latex particles carrying silanol groups on their surface have been synthesized in emulsion polymerization using 3-(trimethoxysilyl)propyl methacrylate (MPS) as a functional comonomer. We showed that the,. colloidal stability of the resulting latex suspensions was highly dependent on PH and on the nature of the surfactant. The structure of the hybrid copolymers was analyzed using infrared and solid-state NMR spectroscopies. Condensation reactions of the silane molecule were promoted at high and low PH and were also influenced by the silane content in the monomer mixture. No condensation products were formed when polymerization was performed at pH 7 using 10 wt % MPS (relative to styrene) indicating that it is possible to control the cross-linking process under these conditions. The functionalization reaction was extended further to poly(methyl methacrylate) and poly(butyl acrylate) latexes. In contrast to polystyrene, condensation products were identified in both cases presumably because of difference in comonomers reactivity ratios, and perhaps also because of difference in molecular mobility. Independent of the microstructure of the hybrid copolymers, AUGER electron spectroscopy and electrophoretic measurements gave evidence of the presence of silanol groups on the particle surface. The SiOH functionality is of great interest in applications where it can be necessary to control the surface properties of polymer colloids. The hybrid copolymers provide rigidity to the surface and can significantly influence mechanical properties of the material. In addition, the SiOH groups can be efficient primers for the subsequent growth of a mineral layer around the particles and can help compatibilize organic colloids with inorganic materials in nanocomposite structures or higher hierarchical devices.