Adsorption of block polymers on well-defined silica surfaces
Block copolymers of polyethylene oxide and polystyrene have been examined in the Surface Force Apparatus and their adsorption on mica is well understood. The results of the measurements suggest that these block copolymers can be subdivided into three compositional groups according to Marques/Joanny theoretical elationships. The main focus of the SFA investigations was to determine the extended length of the polymer brush as this in turn is known to affect the flocculation-deflocculation behavior of particles. This paper describes the use of a “colloidal cell” which can be used to prepare dispersions of silica particles in carbon tetrachloride using a totally evacuated system. The surface of this silica has been defined by heat treatment in vacuo. The cell also enables infrared spectroscopy to be applied to the dispersion. The adsorption of the polymer, the specific interactions of the polyethylene oxide and polystyrene segments with the surface and the rate of settling of the particles can be quantified. Block copolymers with three different asymmetries have been examined and the results compared with data obtained for polyethylene oxide and polystyrene homopolymers.
Key wordsAdsorption silica surfaces block copolymers flocculation
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