Robust Superhydrophobic Energy‐Storage Coatings: Benchmarking and Substituting Fluorinated Chemistries With Eco‐Friendly Alternatives

While fluorine‐free superhydrophobic (SH) coatings and phase change material (PCM)‐integrated SH systems have been reported independently, no prior work has combined natural nanoclay‐reinforced epoxy with fluorine‐free sol–gel chemistry to deliver both SH wettability and high latent heat storage capacity within a single scalable framework. Building on previously established flow‐resistant SH architectures, this work fabricates state‐dependent dual‐functional nanocomposite coatings—superhydrophobic in their native state (contact angles ≈150° and sliding angles ≈3°) and active thermal energy storage materials upon PCM incorporation—using an epoxy matrix reinforced with naturally abundant Halloysite and Sepiolite nanoclays. Reduction of work of adhesion and contact angle hysteresis is achieved through Polysilsesquioxane (PSQ) sol–gel modification using either a conventional fluorosilane or a fluorine‐free alkylsilane alternative, validating trimethoxyoctylsilane as an effective fluorosilane replacement. Systematic variation of formulation demonstrates iluentsy of the porous reentrant architecture leading to paraffin PCM uptake control, with most compositions approaching 50 wt% and the optimized case yielding ≈63 wt% for latent heat storage. Halloysite/alkylsilane composites enhance 10% the PCM loading relative to Halloysite/fluorosilane counterparts; conversely, fluorosilane‐modified formulations exhibit lower work of adhesion. Compositional and synthetic control thus emerges as the key design lever for navigating competing functional demands.