Surface Modification Effect of Poly(perfluorodecene‐co‐vinylamine) on Transparent Poly(methyl methacrylate) Caused by Multiple Covalently‐Connecting Active Sites

ABSTRACT Constructing hydrophobic coatings on transparent poly(methyl methacrylate) (PMMA) with integrated optical transparency and long‐term stability remains a significant challenge. This study develops a multisite covalent anchoring strategy using perfluoroalkyl copolymers to simultaneously maintain high transmittance (> 90%) and durable hydrophobicity. Compared to conventional silane coupling agents—which reduced transmittance by 10% due to micron‐scale agglomeration and suffered > 30° contact angle loss after environmental stress—the covalently anchored copolymer exhibits exceptional performance, retaining > 95% initial contact angle (Δ < 3°) through 10 wastewater exposures while preserving optical clarity. The stable covalent network formed via multipoint backbone bonding to PMMA surfaces minimizes coating delamination and eliminates light‐scattering defects, enabling sustained hydrophobic stability under harsh conditions. This approach resolves the critical stability‐transparency trade‐off in silane‐based modification and provides a viable paradigm for functionalizing optical polymer surfaces through engineered multivalent interfaces.