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

Abstract

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.