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Phase separation of an ionic liquid mixture assisted by a temperature gradient
Ionic liquids have remarkable properties and are commonly harnessed for green chemistry,
lubrication, and energy applications. In this presentation, we report a thermoresponsive ionic
liquid (IL) solution which has the property of phase separating above a critical temperature,
an interesting feature for the recovery of the IL-rich phase. For this purpose, we generate
a temperature gradient in a microfluidic cavity where the confinement strengthens wetting
effects and enhances the demixing. In this experimental configuration, we report the
separation patterns along the phase diagram of the binary mixture composition. Three
separation dynamics regimes are identified that may display complex three-dimensional
flows. In spite of this complexity, we rationalize all the observed regimes. Only two regimes
lead to a complete spatial separation of the two phases. Interestingly, one is reminiscent of
a Marangoni instability in radial geometry, even at confinement below 100 μm.