Polymer depletion profiles around nonspherical colloidal particles.
We study the effect of chain self-avoidance on the polymer density profiles that are induced by a single colloidal particle of nonspherical shape such as an ellipsoid, a dumbbell, or a lens in a solution of nonadsorbing polymers. For colloid sizes sigma much smaller than the size R(x) of the polymers, we observe a pronounced difference between ideal and self-avoiding chains. In the case of ideal polymers, the surfaces of constant density always have the same character as the surface of the particle, e.g., are oblate for an oblate ellipsoid. In the self-avoiding case, however, the character changes with increasing distance r from the particle, and an oblate particle induces prolate surfaces of constant density if sigma<<r<<R(x). For sigma<<r, R(x), the isotropic and anisotropic contributions to the densities factor into a dependence on the particle size and shape and a dependence on r, R(x). The latter is determined by distance distributions within a chain in the absence of the particle. For self-avoiding polymers in two spatial dimensions, exact density profiles are derived for sigma, r<<R(x), which explicitly show the above-mentioned change of the contours of constant density.
Eisenriegler
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Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany.
Bringer
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