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From the Depletion Attraction of the Bridging Attraction: the Effect of Solvent Molecules on the Effective Colloidal Interactions



Jie Chen, Steven R. Kline, Yun Liu


Depletion attraction induced by non-adsorbing polymers or small particles in colloidal solutions has been widely used as a model colloidal interaction to understand aggregation behavior and phase diagrams, such as glass transitions and gelation. However, much less attention has been paid to study the effective colloidal interaction when small particles/molecules can be reversibly attracted to large colloidal particles. At the strong attraction limit, small particles can introduce bridging attraction as it can simultaneously attach to neighbouring large colloidal particles. We use Baxter's multi-component method for sticky hard sphere (SHS) systems to study the bridging attraction and its consequence to phase diagrams, which are controlled by the concentration of small particles and their interaction with large particles. When the concentration of small particles is low, the bridging attraction strength increases very fast with the increase of small particle concentration. The attraction strength eventually reaches a maximum bridging attraction (MBA) concentration. Adding more small particles after the MBA concentration keeps decreasing the attraction strength until reaching a concentration above which the net effect of small particles only introduces an effective repulsion between large colloidal particles. These behaviors are qualitatively different from the concentration dependence of the depletion attraction on small particles, and make phase diagrams very rich for bridging attraction systems. We calculate the spinodal and binodal regions, the percolation lines, the MBA lines, and the equivalent hard sphere interaction line for bridging attraction systems, and have proposed a simple analytic solution to calculation the effective attraction strength using the concentrations of large and small particles. Our theoretical results are found to be qualitatively consistent with experimental results reported recently.
Journal of Chemical Physics


colloid, sticky hard sphere, effective interaction


Chen, J. , Kline, S. and Liu, Y. (2015), From the Depletion Attraction of the Bridging Attraction: the Effect of Solvent Molecules on the Effective Colloidal Interactions, Journal of Chemical Physics, [online], (Accessed June 20, 2024)


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Created February 27, 2015, Updated October 12, 2021