Perturbation of water-ethanol solvent structural relaxation by a bis-urea supramolecular gel and paracetamol

Understanding structural dynamics on the picosecond/nanometer scale in complex fluids is crucial for advancing various fields, from material chemistry to drug delivery. We employ polarized quasi-elastic neutron spectroscopy to investigate the perturbation to the hydrogen bond network of water-ethanol mixtures induced by a supramolecular gel network and by paracetamol (PCM) molecules. Interestingly, while the supramolecular gelator significantly alters the macroscopic behavior of the solvent at concentrations of 0.3 and 0.5 wt. %, it does not affect the hydrogen bond network at the microscopic level. In contrast, the addition of PCM at 5 wt. %, which does not change the macroscopic properties, modifies the structural dynamics of water-ethanol mixtures at length scales commensurate with and below the PCM-PCM correlation length in the mixture. This study reveals the intricate interplay between solute, solvent, and gel interactions, demonstrating a lack of direct correlation between macroscopic and microscopic properties in such complex systems.