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Polymer-Induced Depletion Interaction and Its Effect on Colloidal Sedimentation in Colloid-Polymer MixturesIn this paper we focus on the polymer-induced depletion attraction and its effect on colloidal sedimentation in colloid-polymer mixtures. We first report a small angle neutron scattering (SANS) study of the depletion effect in a mixture of hard-sphere-like colloid and non-adsorbing polymer. Then we present results of our recent sedimentation measurements in the same colloid-polymer mixture. A key parameter in controlling the sedimentation of heavy colloidal particles is the interparticle potential U(tau), which is the work required to bring two colloidal particles from infinity to a distance tau under a give solvent condition. This potential is known to affect the average settling velocity of the particles and experimentally one needs to have a way to continuously vary U(tau) in order to test the theory. The interaction potential U(tau) can be altered by adding polymer molecules into the colloidal suspension. In a mixture of colloid and non-adsorbing polymer, the potential U(tau) can develop an attractive well because of the depletion effect, in that the polymer chains are expelled from the region between two colloidal particles when their surface separation becomes smaller than the size of the polymer chains. The exclusion of polymer molecules from the space between the colloidal particles leads to an unbalanced osmotic pressure difference pushing the colloidal particles together, which results in an effective attraction between the two colloidal particles. The polymer-induced depletion attraction controls the phase stability of many colloid-polymer mixtures, which are directly of interest to industry.
Document ID
19970000424
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Tong, Penger
(Oklahoma State Univ. Stillwater, OK United States)
Date Acquired
August 17, 2013
Publication Date
September 1, 1996
Publication Information
Publication: Third Microgravity Fluid Physics Conference
Subject Category
Nonmetallic Materials
Accession Number
97N10391
Funding Number(s)
CONTRACT_GRANT: NAG3-1613
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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