Abstract
The scattering intensity, from colloidal grains carrying a diffuse adsorbed layer, contains two components: one (Ī (q)) is due to the average concentration profile, and has been considered by the British school; the other component Ī (q) is due to fluctuations in the adsorbed layer. For neutral, flexible, chains, adsorbed from a good solvent, the adsorbed layer is self-similar and should show strong fluctuations. We construct scaling formulae for Ī and Ī in the most relevant regime, where q-1 is larger than a monomer size a, but smaller than a coil size R. For matched grains (no contrast between solvent and grain) the fluctuation effects are sizeable, and scattering is not a very good probe of the inner structure of the adsorbed layer. With mismatched grains, the fluctuation effects are relatively unimportant, and the structure of the average profile should show up as a correction to the Porod law, proportional to q-8/3.