Random packing of mixtures of hard rods and spheres
Seminar Room 1, Newton Institute
AbstractRandom packing of mixtures of hard spherocylinders and hard spheres are studied for $d \approx L$, where $L$ is the length of the spherocylinder and $d$ the diameter of the spheres. Packing fractions of mixtures of hard spherocylindres with aspect ratios $ 4 < L/D < 20$ and how this packing fraction changes with different concentrations of spheres are investigated. The results obtained are compared with observations of mixtures of sterically stabilized rod-like particles and spheres. These colloidal suspensions of rod-like particles are made with sepiolite clays and have previously been found to show liquid crystal behaviour . The addition of spheres to a colloidal rod suspension affects the isotropic-nematic phase transition that occurs in pure suspensions. One might expect that the addition of spheres would lead to a wide phase gap between rod-rich and sphere-rich phases . An experimental study did find some evidence for nematic rod domains with spheres accumulating at their grain boundaries . Very easily however these systems got stuck in gel states consisting of (bundles of) rods trapping spheres . Rather than trying to calculate equilibrium phase diagrams, we are therefore investigating random close packed configurations which may resemble the experimental observations more closely.
References  Z. X. Zhang and J. S. van Duijneveldt, J. Chem. Phys., 124, 154910 (2006).  Henk N.W. Lekkerkerker and Remco Tuinier, Colloids and the Depletion Interaction, Springer, 2011.  N. Yasarawan and J.S. van Duijneveldt, Soft Matter, 6, 353-362 (2010).
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