Geometry Controls Confined Water Dynamics in Lipidic Mesophases

Water under nanoscale confinement is cen-tral to biological function, catalysis, and soft materials,yet how geometry dictates its structure and dynamicsremains unresolved. Here, we establish a direct linkbetween interfacial curvature and confined water behav-ior using an archaeal-inspired phytantriol-water lipidicmesophase platform. By systematically tuning curvatureacross lamellar, double-gyroid cubic, and reverse micellarphases, and integrating structural, thermodynamic, andultrafast spectroscopies, we show that geometry controlsthe dimensionality and mobility of the hydrogen-bondnetwork. Planar interfaces enforce 2D networks that slowdown interfacial water through spatial constrain, whereascurved bicontinuous and micellar topologies promote3D networks with accelerated reorientation. These find-ings reveal a geometric principle for governing waterdynamics in soft nanoconfinement, providing molecularlevel design rules for confined transport and reactivity inmembranes and functional materials.