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Reversible Adsorption and Interfacial Photoisomerization of Azobenzene Surfactants Studied by QCM

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Photoresponsive surfactants offer a versatile approach for remotely controlling interfacial properties through light-triggered isomerization. Among them, azobenzene-based surfactants are particularly attractive due to their structural reversibility and stability under repeated irradiation. In this study, we investigate the dynamic adsorption and desorption behavior of the azobenzene-containing surfactant AzoC 6 at a glass–water interface under controlled UV and blue-light illumination. Using quartz crystal microbalance (QCM) measurements, we show that the interfacial mass change is governed by the isomeric composition in the bulk solution: the trans isomer exhibits strong adsorption, while the cis isomer is significantly less surface-active. We further quantify the photoisomerization kinetics at the interface, revealing that the isomerization rate constant decreases with a lower trans isomer concentration due to a transition from a diffuse multilayer to a confined double-layer structure. At higher concentrations, the rapid exchange between trans and cis isomers sustains dynamic interfacial rearrangements, facilitating the formation of spatial isomer gradients. These gradients generate light-driven diffusio-osmotic flows, with a time evolution that reflects the interfacial photoresponse. Our findings provide mechanistic insight into light-induced interfacial processes and highlight the potential of azobenzene surfactants for designing stimuli-responsive systems and soft materials with remote, reversible control.

Source: Langmuir

DOI: 10.1021/acs.langmuir.5c03617

Authors: Maren Umlandt, Philipp Ortner, Nino Lomadze, Marek Bekir, Svetlana Santer, Yulia D. Gordievskaya

Institution: University of Potsdam

Language: English

Topic: Photochromic and Fluorescence Chemistry

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,500

Funder: Deutsche Forschungsgemeinschaft