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

Area of Science:

• Materials Science
• Physical Chemistry
• Chemical Engineering

Background:

• Eutectogels (ETGs) are versatile materials derived from deep eutectic solvents (DESs), gelators, and water.
• Their applications in separations, catalysis, and energy storage depend critically on temperature-dependent molecular diffusion and intermolecular interactions.

Purpose of the Study:

• To investigate the temperature-dependent molecular diffusion of Alexa Fluor 633 and ATTO 647N in choline chloride:2glycerol (glyceline) DESs and corresponding ETGs.
• To evaluate the impact of water content (10% and 20% w/w) and temperature cycling on diffusion and material properties.

Main Methods:

• Fluorescence Recovery After Photobleaching (FRAP) was used to measure molecular diffusion coefficients from 20 to 100 °C.
• Differential Scanning Calorimetry (DSC) and Raman spectroscopy were employed to analyze thermal properties and intermolecular interactions.

Main Results:

• ETGs showed faster molecular diffusion than dry DESs, attributed to their porous, 3D structure, despite higher viscosity.
• An irreversible decrease in diffusion coefficients was observed in ETGs after temperature cycling, correlating with a shift in glass transition temperature.
• Raman data indicated no significant changes in intermolecular interactions with temperature or water content.

Conclusions:

• The study elucidates the complex interplay between viscosity, structure, and molecular diffusion in ETGs.
• Findings provide crucial insights into the thermal stability and diffusion dynamics of ETGs, essential for optimizing their performance in various applications, especially under cyclic temperature conditions.