One‐Step Solvent‐Free Dual‐Curing Strategy for Fluorine‐Free Omniphobic Coatings: Synchronizing High Transparency, Durability, and Antifouling in Underwater Optical Systems

While liquid‐like surfaces show promise for protecting underwater optical systems against biofouling and mechanical degradation, creating transparent, fluorine‐free omniphobic coatings that combine mechanical robustness with flexibility and long‐term durability remains a critical unmet challenge. Here, an innovative dual‐curing hybrid approach is reported that synergistically incorporates multi‐functional polymers within an epoxy matrix to form a densely cross‐linked yet flexible network. This unique architecture achieves an unprecedented balance of high hardness (7–9H) and extreme flexibility (10 000 bending cycles, bending radius = 1 mm). The interpenetration of organosilicons confers exceptional omniphobicity and anti‐adhesion characteristics, enabling low‐surface‐tension liquids to slide off readily (sliding angle < 4.1°). Fabricated through an environmentally benign, one‐step, solvent‐free process, the optimized coating demonstrates remarkable substrate adhesion (5B) and exceptional wear resistance, ensuring reliable operation in demanding underwater environments. The highly cross‐linked network maintains exceptional stability in aggressive liquid media without compromising optical transparency (> 99.1%). This work not only overcomes the fundamental trade‐off between mechanical robustness and flexibility but also establishes a generalizable platform for designing high‐performance protective coatings for marine optical applications.