The technique of photo correlation spectroscopy has been exploited in studies of the hydrodynamic thickness of polyvinyl alcohol (_w= 45000) adsorbed on monodisperse polystyrene latex particles. Complications can arise from particle interactions, especially aggregation effects. A procedure has been devised to quantify these and allow for their presence in the interpretation of the photo correlation measurements. This has involved the development of a low angle scattering approach which enables the second virial coefficients of particles to be measured, and which can be exploited with concentrated latices.

An unexpected dependence of adsorbed layer thickness on polymer solution concentration was observed with a region of negative slope. Theoretical consideration of the requirements for such behaviour suggested that in principle it is possible in the circumstance of a very high adsorption affinity of the polymer for the surface and a solvent condition only very slightly better than the θ-condition. In the context, however, of the isotherm published for the system under study, the behaviour cannot readily be understood.