Discerning optimum water content in novel bio-based, macrocycle containing des formulations via viscosity measurements

Deep eutectic solvents (DESs), particularly those incorporating bio-based and macrocyclic components, represent a frontier in the design of sustainable, tunable media for advanced functional materials [1(a-c)]. In this work, we investigate the rheological behavior of a novel supramolecular DES consisting of a proper mixture of the C-Methyl resorcin[4]arene macrocycle with acetylcholine chloride and water. Three of such ternary blends, differing in their water content, were characterized using steady-state shear rheology across a temperature range of 20–90 °C to elucidate the impact of water as a structural modulator. All formulations exhibited Newtonian flow behavior at lower temperatures, transitioning to pseudoplasticity at elevated temperature. The results underscore the pivotal role of water in altering hydrogen-bonding networks and dynamic molecular interactions, thereby tuning the viscoelastic profile of the studied DES. The observed interplay between water content and flow behavior highlights an optimal hydration window, critical for preserving desirable rheological properties, with a huge impact on the design of bio-derived DESs and their applications in green chemistry, catalysis, and soft materials engineering. Our findings contribute to the growing understanding of structure–property relationships in macrocycle-containing eutectic systems and reinforce the necessity of water activity control in their functional development.