Temperature gradient induced solvent coarsening around colloids

8 Sep 2017, 10:15
15m
oral Session 12

Speaker

Anna Maciolek (ICHF PAN)

Description

Using mesoscopic numerical simulations and analytical theory we investigate the coarsening of the solvent structure around a colloidal particle emerging after a temperature quench of the colloid surface. Qualitative differences in the coarsening mechanisms are found, depending on the composition of the binary liquid mixture forming the solvent and on the adsorption preferences of the colloid. For an adsorptionwise neutral colloid, as function of time the phase being next to its surface alternates. This behavior sets in on the scale of the relaxation time of the solvent and is absent for colloids with strong adsorption preferences. A Janus colloid, with a small temperature difference between its two hemispheres, reveals an asymmetric structure formation and surface enrichment around it, even if the solvent is within its one-phase region and if the temperature of the colloid is above the critical demixing temperature $T_c$ of the solvent. A comparison between the emerging fluid structures above and below $T_c$ is provided. Our phenomenological model turns out to capture recent experimental findings according to which, upon laser illumination of a Janus colloid and due to the ensuing temperature gradient between its two hemispheres, the surrounding binary liquid mixture develops a concentration gradient.

Primary author

Anna Maciolek (ICHF PAN)

Co-authors

Siegfried Dietrich (MPI for Intelligent Systems) Sutapa Roy (MPI for Intelligent Systems, Stuttgart)

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