Synthesis and interfacial activity of pH-responsive poly(2-vinylpyridine) microgels

Steven P. Armes, Department of Chemistry, The University of Sheffield

04 June 2009 at 09:30

Location: JHE 342

A series of six near-monodisperse, sterically-stabilised poly(2-vinylpyridine) latexes ranging from 360 to 970 nm diameter are synthesised via aqueous emulsion polymerisation.1 The kinetics of the latex-to-microgel acid-induced swelling transition is studied using a stopped-flow pH jump technique: characteristic swelling times are of the order of tens of milliseconds and smaller particles swell faster than larger particles, as predicted by the Tanaka equation.2, 3 Images of swollen microgels can be obtained directly in aqueous solution using x-ray microscopy. Adsorption of these particles at the mica/water and oil/water interfaces is also investigated.4,5 Two different macromonomers are examined as steric stabilisers: a commercially available methoxy-capped poly(ethylene glycol) monomethacrylate and a tailor-made styrene-functionalised poly(2-dimethylamino)ethyl methacrylate). Steric stabiliser contents are estimated by 1H NMR spectroscopy and x-ray photoelectron spectroscopy studies confirm that both stabilisers are present at the particle surface, as expected. Judicious selection of the steric stabiliser allows the production of pH-responsive Pickering-type emulsions and foams.5,6

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