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arXiv · 0905.3393

The role of weak charging in metastable colloidal clusters

Christian L. Klix·Ken-ichiro Murata·Hajime Tanaka·Stephen R. Williams·Alex Malins·C. Patrick Royall
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Abstract

We study metastable clusters in a colloidal system with competing interactions. A short-ranged polymer-induced attraction drives clustering, while a weak, long-ranged electrostatic repulsion prevents extensive aggregation. We compare experimental yields of cluster structures expected from theory, which assumes simple addition of the competing isotropic interactions. For clusters of size $4\leq m\leq6$, the yield is significantly less than that expected. We attribute this to an anisotropic self-organized surface charge distribution linked to the cluster symmetry: non-additivity of electrostatic repulsion and polymer-induced attraction. 7-membered clusters have a clear optimal yield of the expected pentagonal bipyramid structure as a function of strength of the attractive interaction.

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Christian L. Klix, Ken-ichiro Murata, Hajime Tanaka, Stephen R. Williams, Alex Malins, C. Patrick Royall. 2009-05-20. The role of weak charging in metastable colloidal clusters. https://doi.org/10.1038/srep02072

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