By using a classical density functional theory (interfacial statistical associating fluid theory), we investigate the structure and effective forces in nonadsorbing polymer-colloid mixtures. The theory is tested under a wide range of conditions and performs very well in comparison to simulation data. A comprehensive study is conducted characterizing the role of polymer concentration, particle/polymer-segment size ratio, and polymer chain length on the structure, polymer induced depletion forces, and the colloid-colloid osmotic second virial coefficient. The theory correctly captures a depletion layer on two different length scales, one on the order of the segment diameter (semidilute regime) and the other on the order of the polymer radius of gyration (dilute regime). The particle/polymer-segment size ratio is demonstrated to play a significant role on the polymer structure near the particle surface at low polymer concentrations, but this effect diminishes at higher polymer concentrations. Results for the polymer-mediated mean force between colloidal particles show that increasing the concentration of the polymer solution encourages particle-particle attraction, while decreasing the range of depletion attraction. At intermediate to high concentrations, depletion attraction can be coupled to a midrange repulsion, especially for colloids in solutions of short chains. Colloid-colloid second virial coefficient calculations indicate that the net repulsion between colloids at low polymer densities gives way to net attraction at higher densities, in agreement with available simulation data. Furthermore, the results indicate a higher tendency toward colloidal aggregation for larger colloids in solutions of longer chains.
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28 April 2008
Research Article|
April 30 2008
Microstructure and depletion forces in polymer-colloid mixtures from an interfacial statistical associating fluid theory
Adam Bymaster;
Adam Bymaster
a)
Department of Chemical and Biomolecular Engineering,
Rice University
, 6100 S. Main, Houston, Texas 77005, USA
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Shekhar Jain;
Shekhar Jain
Department of Chemical and Biomolecular Engineering,
Rice University
, 6100 S. Main, Houston, Texas 77005, USA
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Walter G. Chapman
Walter G. Chapman
b)
Department of Chemical and Biomolecular Engineering,
Rice University
, 6100 S. Main, Houston, Texas 77005, USA
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a)
Electronic mail: [email protected].
b)
Author to whom correspondence should be addressed. Tel.: (1)713.348.4900. FAX: (1)713.348.5478 Electronic mail: [email protected].
J. Chem. Phys. 128, 164910 (2008)
Article history
Received:
February 20 2008
Accepted:
March 25 2008
Citation
Adam Bymaster, Shekhar Jain, Walter G. Chapman; Microstructure and depletion forces in polymer-colloid mixtures from an interfacial statistical associating fluid theory. J. Chem. Phys. 28 April 2008; 128 (16): 164910. https://doi.org/10.1063/1.2909975
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