Quasielastic Neutron Scattering Reveals Anisotropic Water Transport in Smectite Thin Film

Clay minerals exhibit complex interactions with water that critically influence their functional properties, yet the anisotropic nature of water dynamics in smectite thin films remains underexplored. Here quasielastic neutron scattering (QENS) is employed on oriented sodium beidellite films to investigate water mobility across multiple timescales and orientations. Analysis reveals pronounced anisotropic water dynamics, characterized by confinement perpendicular to the clay layers and orientation‐dependent diffusion coefficients and residence times. These dynamics correlate with structural features, including interlayer cation spacing and anomalies in the hydroxyl group absorbance. The findings elucidate directional transport and confinement phenomena in layered smectites, providing fundamental insights that can guide the design of clay‐based materials with tailored transport and interfacial properties.