Séminaire

Tuesday 8 September 2026 à 11h00.

Dielectric response as a source of viscosity in polar liquids

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Transport coefficients and dielectric relaxation in liquids are often treated as distinct properties. We show that, in polar liquids, orientational dipolar fluctuations generate a substantial contribution to the shear viscosity which can be expressed in terms of dielectric response parameters. We derive an explicit relation linking the dipolar contribution to viscosity to the static permittivity and the Debye relaxation time. With a single microscopic cutoff length fixed from one temperature, the theory predicts the temperature dependence of the viscosity for water and several alcohols using independently measured dielectric data. The results identify a general mechanism by which slow polarization dynamics generate an appreciable (for strongly polar liquids, dominant) contribution to the viscosity, providing a quantitative bridge between dielectric spectroscopy and rheology.

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