Short-ranged attractions in jammed liquids: How cooling can melt a glass

Abstract

We demonstrate that an extended picture of kinetic constraints in glass-forming liquids is sufficient to explain dynamic anomalies observed in dense suspensions of strongly attracting colloidal particles. We augment a simple model of heterogeneous relaxation with static attractions between facilitating excitations, in a way that mimics the structural effect of short-ranged interparticle attractions. The resulting spatial correlations among facilitated and unfacilitated regions give rise to new relaxation mechanisms that account for non-monotonic dependence of relaxation times on attraction strength as well as logarithmic decay of density correlations in time. These unusual features are a simple consequence of spatial segregation of kinetic constraints, suggesting an alternative physical perspective on attractive colloids than that suggested by mode-coupling theory. Based on the behavior of our model, we predict a crossover from super-Arrhenius to Arrhenius temperature dependence as attractions become dominant at fixed packing fraction.

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• Phase-field model of long-time glass-like relaxation in binary fluid mixtures
• Logarithmic Relaxation in a Kinetically Constrained Model
• Glassy behaviour of sticky spheres: What lies beyond experimental timescales?
• Crossover behavior and multi-step relaxation in a schematic model of the cut-off glass transition
• Anomalous relaxation in binary mixtures: a dynamic facilitation picture
• Two-stage coarsening mechanism in a kinetically constrained model of an attractive colloid