SURFACE MODIFICATION OF KAOLIN .1. COVALENT ATTACHMENT OF POLYETHYLENE-GLYCOL USING A URETHANE LINKER

The kaolin surface was modified through surface reaction in order to t ailor the colloidal behaviour of the particles. A molecular weight ser ies of polyethylene glycols was attached to the surface hydroxyls, usi ng a urethane linker, by reaction with toluene 2,4-diisocyanate. The c hange in the surface was monitored and the surface products identified using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DR IFTS) and solid-state carbon-13 NMR spectroscopy. The strength of atta chment was evaluated by extraction with solvents for urethanes and pol y(ethylene oxides). The surface coverage of polymer chains was quantif ied using a combination of two methods. Potentiometric titration was u sed to determine the amount of urethane formed on the surface and the number of terminal isocyanate groups available for subsequent reaction with the hydroxy-terminated polymer. The grafting density of poly(eth ylene oxide) on to the kaolin surface was determined through elemental analysis.