Sedimentation stacking diagrams of binary mixtures of thick and thin hard rods

Abstract

We use Onsager theory and the local density approximation to study sedimentation-diffusion equilibrium density profiles of binary mixtures of thick and thin hard rods. We construct stacking diagrams for three diameter ratios, and find that even a simple spindle-shaped phase diagram with only isotropic-nematic demixing can lead to counter-intuitive stacking sequences such as an isotropic phase sandwiched between two nematic phases. For the most complex phase diagram considered here, we find sixteen distinct stacking sequences, including several with five sedimented layers. By adding sedimentation paths to composition-pressure and density-density phase diagrams and calculating density and composition profiles, we show that conclusions about bulk phase diagrams of binary mixtures on the basis of sedimentation-diffusion equilibria should be drawn warily.

arXiv comment9 pages, 8 figures, extended discussion in section 4, added references, minor changes to figures (results unchanged)

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Cited by in corpus (5)

• Gravity-induced phase phenomena in plate-rod colloidal mixtures
• The role of sample height in the stacking diagram of colloidal mixtures under gravity
• Demixing and tetratic ordering in some binary mixtures of hard superellipses
• Sedimentation of colloidal plate-sphere mixtures and inference of particle characteristics from stacking sequences
• Sedimentation path theory for mass-polydisperse colloidal systems