Adsorption of semi-dilute polymer solutions on fractal colloidal grains

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Abstract
We study the adsorption of a semidilute polymer solution on small colloidal grains with a fractal surface of dimension D (5/3 < D < 3) focusing on the concentration profile around the grain and on the adsorbance which is the total number of monomers belonging to adsorbed chains. On large grains (flat surfaces) the concentration profile is self-similar. The adsorbance is equal to the surface excess at concentrations close to the overlap concentration Ø * but is larger in a concentrated solution, adsorbed chains making large loops in the solution. On small grains a rather large variety of scaling behavior is found. If the grain size is smaller than the solution correlation length, the self-similar profile extends up to distances of the order of the grain radius ; further away the concentration decays more rapidly towards its bulk value. The adsorbance is determined by the surface geometry in dilute solutions. At higher concentrations, the solution can be considered as a melt of blobs