Authors

Citation

Y. Mao et al., DEPLETION FORCE IN COLLOIDAL SYSTEMS, Physica. A, 222(1-4), 1995, pp. 10-24

Citations number

36

Language

INGLESE

art.tipo

Article

Categorie Soggetti

Physics

Journal title

ISSN journal

0378-4371

Volume

222

Issue

1-4

Year of publication

1995

Pages

10 - 24

Database

ISI

SICI code

0378-4371(1995)222:1-4<10:DFICS>2.0.ZU;2-8

Abstract

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 large spheres (of
radius R) in a dilute solution of mutually avoiding small spheres (of
diameter sigma much less than R and volume fraction phi), to third ord
er in phi. In addition to the well-known attractive force for 0 < h <
sigma, we find a repulsive barrier at larger separations, and beyond t
hat a secondary minimum. Except for unusually large size ratios (perha
ps abetted by relatively high density phi), these features of the inte
raction potential are too small, compared to k(B)T, for kinetic stabil
ization (arising from the barrier) or flocculation into the secondary
minimum, to be widespread, although such effects are possible in princ
iple. For feasible size ratios, the same features should have observab
le consequences for the radial distribution function of the large sphe
res. Such effects can be viewed as precursors, at low density, of liqu
idlike structuring (solvation forces) expected at higher phi. Our thir
d order calculation gives satisfactory agreement with a recent compute
r simulation at moderate density and size ratio (2R/sigma = 10; phi =
pi/15).