As first explained by the classic Asakura–Oosawa (AO) model, effective attractive forces between colloidal particles induced by depletion of nonadsorbing polymers can drive demixing of colloid–polymer mixtures into colloid-rich and colloid-poor phases, with practical relevance for purification of water, stability of foods and pharmaceuticals, and macromolecular crowding in biological cells. By idealizing polymer coils as effective penetrable spheres, the AO model qualitatively captures the influence of polymer depletion on thermodynamic phase behavior of colloidal suspensions. In previous work, we extended the AO model to incorporate aspherical polymer conformations and showed that fluctuating shapes of random-walk coils can significantly modify depletion potentials [W. K. Lim and A. R. Denton, Soft Matter 12, 2247 (2016); J. Chem. Phys. 144, 024904 (2016)]. We further demonstrated that the shapes of polymers in crowded environments sensitively depend on solvent quality [W. J. Davis and A. R. Denton, J. Chem. Phys. 149, 124901 (2018)]. Here, we apply Monte Carlo simulation to analyze the influence of solvent quality on depletion potentials in mixtures of hard-sphere colloids and nonadsorbing polymer coils, modeled as ellipsoids whose principal radii fluctuate according to random-walk statistics. We consider both self-avoiding and non-self-avoiding random walks, corresponding to polymers in good and theta solvents, respectively. Our simulation results demonstrate that depletion of polymers of equal molecular weight induces much stronger attraction between colloids in good solvents than in theta solvents and confirm that depletion interactions are significantly influenced by aspherical polymer conformations.
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28 August 2021
Research Article|
August 25 2021
Influence of solvent quality on depletion potentials in colloid–polymer mixtures
Special Collection:
Depletion Forces and Asakura-Oosawa Theory
Alan R. Denton
;
Alan R. Denton
a)
Department of Physics, North Dakota State University
, Fargo, North Dakota 58108-6050, USA
a)Author to whom correspondence should be addressed: alan.denton@ndsu.edu
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Wyatt J. Davis
Wyatt J. Davis
Department of Physics, North Dakota State University
, Fargo, North Dakota 58108-6050, USA
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a)Author to whom correspondence should be addressed: alan.denton@ndsu.edu
Note: This paper is part of the JCP Special Topic on Depletion Forces and Asakura-Oosawa Theory.
J. Chem. Phys. 155, 084904 (2021)
Article history
Received:
June 25 2021
Accepted:
August 07 2021
Citation
Alan R. Denton, Wyatt J. Davis; Influence of solvent quality on depletion potentials in colloid–polymer mixtures. J. Chem. Phys. 28 August 2021; 155 (8): 084904. https://doi.org/10.1063/5.0061370
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