Long flexible polymers interacting with ellipsoids, cylinders, and needles.
The depletion interactions of ellipsoidal colloidal particles in a solution of long polymer chains are analyzed. Of primary concern are the limiting cases in which the ellipsoid reduces to a cylinder of infinite length and finite radius and a "needle" of finite length and vanishing radius. Relations are obtained between the polymer effects induced by a needle that is much shorter than the polymer size and by a cylinder with radius much smaller than the polymer size. These imply exact quantitative results for the orientation-dependent depletion interaction between a short needle and a wall. Qualitative differences between the needle and thin disk are discussed.
Eisenriegler
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Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany. e.eisenriegler@fz-juelich.de