J. Phys. II France
Volume 5, Numéro 12, December 1995
Page(s) 1761 - 1766
DOI: 10.1051/jp2:1995213
J. Phys. II France 5 (1995) 1761-1766

Depletion Force in Polydisperse Systems

Y. Mao

Cavendish Laboratory, Madingley Road, Cambridge, CB3 OHE, UK

(Received 21 September 1995, accepted 11 October 1995)

The entropic depletion force, in colloids, arises when large particles are placed in a solution of smaller ones, and sterically constrained to avoid them. We calculate the interaction between two flat plates or large hard spheres (of radius R) in a solution of small and polydisperse hard spheres (of average diameter $\bar{\sigma} \ll R$) to second order in small sphere concentration. We find that the effect of polydispersity is to generally smoothen out the depletion force while maintaining the recently predicted repulsive barrier; but for high polydispersities, the repulsion could be eventually wiped out.

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