Temperature-Dependent Molecular Diffusional Properties in Deep Eutectic Solvents and Eutectogels

Journal Article · Tue Aug 05 00:00:00 EDT 2025 · Langmuir

DOI:https://doi.org/10.1021/acs.langmuir.5c01521· OSTI ID:2998109

Masching, Hayley P. ^[1]; Stephens, Nicole M. ^[1]; Abbasi, Nabeel Mujtaba ^[1]; Anderson, Jared L. ^[1]; Smith, Emily A. ^[1]

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1. Ames Laboratory (AMES), Ames, IA (United States); Iowa State Univ., Ames, IA (United States)

Eutectogels (ETGs) prepared from deep eutectic solvents (DESs), a gelator, and water have many uses in separations, catalysis, and energy storage systems. In these applications, temperature-dependent molecular diffusional properties and intermolecular interactions play a critical role in their function. Diffusional properties of Alexa Fluor 633 and ATTO 647N were measured across a range of temperatures in choline chloride:2glycerol DESs comprised of one molar equivalent of choline chloride and two molar equivalents of glycerol (also known as glyceline) as well as ETGs made from this DES, a xanthan gum gelator, and 10% w/w water or 20% w/w water. Fluorescence recovery after photobleaching (FRAP) was employed to evaluate potential changes in molecular diffusion within DESs and ETGs from 20 to 100 °C. Surprisingly, the ETGs have a larger sample viscosity but also exhibit faster molecular diffusion when compared to the dry DES. This is attributed to macroscopic properties of the ETGs (e.g., pores, three-dimensional structure). The FRAP data also show an irreversible temperature-dependent decrease in the diffusion coefficient of both fluorophores in the ETGs. This is consistent with differential scanning calorimetry data of the ETG, which shows a shift to a more negative glass transition temperature (−36 °C to −47 °C) after the first cooling/heating cycle. Raman data reveal no detectable changes in the intermolecular interactions in either the DESs or ETGs as a function of temperature or water content. Finally, the findings on temperature- and water-dependent diffusional properties of DESs and ETGs provide a foundation for optimizing the use of these materials across various applications, particularly where repeated heating/cooling cycles may be used.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB)
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 2998109
• Journal Information: Langmuir, Journal Name: Langmuir Journal Issue: 32 Vol. 41; ISSN 0743-7463; ISSN 1520-5827
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

alcohols
diffusion
fluorophores
viscosity