Three birds with one stone: rational design of organic–inorganic hybrid nanoclusters for high-performance liquid-like coatings†

Achieving transparent polymer coatings that combine hardness and flexibility is fundamentally limited by the filler-induced trade-off between mechanical reinforcement and optical clarity. Here, a polyhedral oligomeric silsesquioxane-based (P-type) nanocluster is synthesized for high-performance liquid-like (HPLL) coating. In synergy with hyperbranched epoxy–oligosiloxane (H-type) nanoclusters, the resulting coating exhibits exceptional properties: pencil hardness up to 9H, flexibility down to a 1.5 mm bending diameter, optical transparency comparable to that of bare glass, and omniphobicity characterized by contact angle hysteresis below 10° across diverse liquids. As the P-type nanocluster content increases from 0 to 25%, the coating's hardness and elastic modulus increase by 25.91% and 17.48%, respectively, compared to the pure H-type nanocluster coating. Additionally, it significantly improves adhesion to various substrates, such as glass, epoxy-glass fiber, steel, and polyethylene glycol terephthalate (PET). Moreover, the upward migration capability of the polymer brush imparts robustness to the coating. The HPLL coating also serves as a stable corrosion barrier for a Cu alloy during anti-corrosion testing. These results underscore the potential of P-type nanoclusters to achieve a “three birds with one stone” strategy—surface-directed assembly, high crosslinking density, and a fluorine-free system.