THE KINETICS OF PARTICLE AND POLYMER ADSORPTION BY TOTAL INTERNAL-REFLECTION FLUORESCENCE

A spectrofluorimeter has been adapted to produce and analyse total internal reflection phenomena at solid-liquid interfaces. The induced evanescent wave is used to excite fluorescent species at the surface, and a specially constructed flow cell enables interfacial processes to be followed under well-defined hydrodynamic conditions. The adsorption of aqueous dispersions of cationic polystyrene latex particles and the amphoteric poly(dimethyldiallyl-ammonium chloride co-acrylic acid) onto a flat quartz surface has been studied as a function of time. For particle adsorption the data fit a single-exponential equation which is interpreted in terms of the rate of mass transfer to the surface. Polymer adsorption is more complex and the data fit a double-exponential rate equation at low bulk concentrations. At higher polymer concentrations an early-time maximum is observed, which is explained in terms of the relative rates of mass transfer to the surface and configurational rearrangement of adsorbed molecules.