Dynamic Supramolecular Eutectogels with Reversible Light Driven Reconfiguration

Résumé :

Deep eutectic solvents (DESs) constitute a highly tunable class of liquid media formed by the association of two or more components (e.g., a hydrogen-bond donor and an organic salt), whose extensive hydrogen bonding interactions result in a pronounced depression of the melting point. Their composition-dependent physicochemical properties make DESs particularly attractive for directing the self-assembly of functional soft materials [1,2]. In this context, eutectogels (gels formed within DES media), offer a versatile platform in which solvent–solute interactions can be exploited to modulate macroscopic material properties beyond those dictated by the gelator alone [3].

Herein, we report a versatile strategy for the design of light-responsive eutectogels with intrinsically tunable mechanical properties. The approach relies on the supramolecular co-assembly of an amphiphilic component with a rationally designed azobenzene derivative engineered for high solubility in water-free DES media. Through complementary characterization across molecular and mesoscale length scales, we provided a detailed understanding of the heterotypic interactions underlying the formation of elongated, one-dimensional supramolecular networks. We further establish that photoisomerization of the azobenzene units induces pronounced rearrangements of these networks, providing a molecular-level mechanism for controlling the material’s hierarchical organization.

Upon ultraviolet irradiation, this molecular reconfiguration leads to an abrupt gel-to-sol transition, effectively erasing the material’s solid-like mechanical response. Subsequent exposure to visible light reverses the process, restoring the gel state and recovering a mechanically robust network that remains stable during prolonged storage without appreciable loss of performance. Remarkably, the optically driven transition is highly reversible and cyclable, enabling repeated switching between gel and sol states without detectable deterioration of structural integrity or mechanical properties. Collectively, these results demonstrate how molecular photochemical events can be translated into reversible macroscopic mechanical actuation, establishing DES-based supramolecular eutectogels as promising platforms for dynamically reconfigurable soft matter.

References :
[1] Hansen, B. et al., Chem. Rev. 2021, 101, 1232-1285.
[2] P. A. Mercadal, A. González, A. Beloqui, L. C. Tomé, D. Mecerreyes, M. Calderón and M. L. Picchio, JACS Au, 2024, 4, 3744-3758.
[3] A. Sanchez-Fernandez, J. F. Poon, A. E. Leung, S. F. Prevost and C. Dicko, ACS Nano, 2024, 18, 18314-18326.

Orsolya Czakkel (College 9 Secretary)

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