Isochronal superpositioning in the equilibrium regime of superpressed propylene carbonate to ∼ 1.8 GPa: A study by diffusivity measurement of the fluorescent probe Coumarin 1 - CEA - Commissariat à l’énergie atomique et aux énergies alternatives Accéder directement au contenu
Article Dans Une Revue European Physical Journal E: Soft matter and biological physics Année : 2019

Isochronal superpositioning in the equilibrium regime of superpressed propylene carbonate to ∼ 1.8 GPa: A study by diffusivity measurement of the fluorescent probe Coumarin 1

Résumé

We address the problem of glass-forming of liquids by superpressing. We study the pressure-induced dynamic change of the fragile van der Waals liquid propylene carbonate towards the glassy state in the equilibrium regime by measuring the diffusivity of the fluorescent probe Coumarin 1 embedded in the host liquid. The probe diffusivity is measured by the fluorescence recovery after photobleaching (FRAP) technique across a bleached volume generated by the near-field diffracted pattern of a laser beam. The recovered fluorescence intensity fits to a stretched exponential with the diffusive time tau and the stretched exponent beta as free parameters. In the pressure range [0.3-1.0] GPa the diffusivity decouples from the Stokes-Einstein relation. The decoupling correlates well to a decrease of beta. The variation of beta is non-monotonous with t showing a minimum at tau similar to 10(3) s. We evidence an isochronal superpositioning over about 3 decades of tau between similar to 10 s and similar to 3 x 10(3) s and a density scaling in the whole investigated pressure range. The pressure at which beta is minimum coincides to the dynamical crossover pressure measured by other authors. This crossover pressure is compatible with the critical point of MCT theory. As our studied pressure range encompasses the critical pressure, the non-monotonous variation of beta opens new insight in the approach to the critical point.
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Dates et versions

cea-04344836 , version 1 (14-12-2023)

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Marco Bonetti, Alizée Dubois. Isochronal superpositioning in the equilibrium regime of superpressed propylene carbonate to ∼ 1.8 GPa: A study by diffusivity measurement of the fluorescent probe Coumarin 1. European Physical Journal E: Soft matter and biological physics, 2019, 42 (8), pp.97. ⟨10.1140/epje/i2019-11861-4⟩. ⟨cea-04344836⟩
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