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Depletion Stabilization by Semidilute Rods

Y. Mao tex2html_wrap_inline23 , M. E. Cates tex2html_wrap_inline25 and H. N. W. Lekkerkerker tex2html_wrap_inline27

tex2html_wrap_inline23 Cavendish Laboratory, Madingley Road,
Cambridge, CB3 OHE, UK.

tex2html_wrap_inline25 Department of Physics and Astronomy,
University of Edinburgh, King's Buildings,
Mayfield Road, Edinburgh EH9 3JZ, UK.

tex2html_wrap_inline27 Van't Hoff Laboratory, University of Utrecht,
Padualaan 8, 3584 Utrecht, The Netherlands.


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 hard spheres (of radius R) in a semidilute solution of hard rods of length L and diameter D ( tex2html_wrap_inline41 ) to second order in rod concentration. In addition to the well-known attractive force for separations less than L, we find a repulsive force between the spheres at larger separations. For semidilute rods, the resulting barrier can be large compared to tex2html_wrap_inline45 , permitting kinetic stabilization.

Yong Mao
Tue Apr 22 14:41:20 BST 1997