Issue 44, 2024

Microrheology of gemini surfactants at interfaces and in solutions in the dilute and semidilute regimes

Abstract

Gemini surfactants are ideal systems to study a wide range of rheological behaviours in soft matter, showing fascinating analogies with living polymers and polyelectrolytes. By only changing the concentration, the shear viscosity can vary by 7 orders of magnitude in the bulk when transitioning through the semidilute regime. In order to elucidate on the intrinsic shear viscosity profile at the interface in soft matter systems manifesting various concentration regimes and morphological transitions, we performed microrheology and adsorption experiments under a wide range of experimental conditions. The surface shear viscosity has been characterized by passive microrheology, tracking Brownian particles trapped at the air–solution interface, under particle wetting conditions precisely characterized by interferometry. We observe that a steep increase in bulk shear viscosity as a function of the concentration does not translate at the interface, which may show a negative surface shear viscosity. By comparing macrorheology and microrheology, we measure significant differences both at the interface and in the bulk in the semidilute regime, where wormlike micelles start to entangle. The disparity in rheological measurements can be attributed to notable depletion effects near both the air–solution and particle–solution interfaces.

Graphical abstract: Microrheology of gemini surfactants at interfaces and in solutions in the dilute and semidilute regimes

Supplementary files

Article information

Article type
Paper
Submitted
15 Jul 2024
Accepted
17 Oct 2024
First published
18 Oct 2024

Soft Matter, 2024,20, 8835-8844

Microrheology of gemini surfactants at interfaces and in solutions in the dilute and semidilute regimes

M. Medfai, A. Stocco, C. Blanc, M. Nobili and M. In, Soft Matter, 2024, 20, 8835 DOI: 10.1039/D4SM00860J

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