Concentration-dependent wetting behavior of CaCl2-water droplets on a calcium-silicate-hydrate surface: Molecular insights into ion hydration and interfacial interaction

XR Hua and X Chen, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 727, 138309 (2025).

DOI: 10.1016/j.colsurfa.2025.138309

Understanding the concentration-dependent wetting behavior of ionic droplets on calcium-silicate-hydrate (C-SH) substrates is critical for advancing applications in cement hydration, energy storage, and materials science. This study systematically investigates the effect of CaCl2 concentration on droplet wetting, water structure, and ion dynamics through molecular dynamics simulations. By analyzing contact angle evolution, mean square displacement (MSD), radial distribution functions (RDF), and hydrogen bonding, it was revealed that increasing CaCl2 concentration enhances intradroplet cohesion while weakening droplet-substrate adhesion. At higher concentrations, ionic hydration and clustering disrupt the water network, reducing water mobility and hydrogen bonding. This leads to limited droplet spreading and higher equilibrium contact angles, a key finding providing molecular-level insights into concentration-dependent wettability changes. This work bridges a significant research gap in understanding ionic effects on nanoscale droplet wetting and offers fundamental insights relevant to material design and interface engineering.

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