Dual-repairable superhydrophobic coatings based on functionalized heterogeneous cellulose crystals and polydimethylsiloxane enabled by dynamic Diels-Alder chemistry.

Superhydrophobic surfaces frequently exhibit performance degradation in practical applications owing to the simultaneous deterioration of low-surface-energy components and micro-nano structures under chemical and mechanical stresses. To address this issue, designing self-repairable structures has emerged as a pivotal strategy for enhancing the long-term durability of superhydrophobic materials. However, the development of superhydrophobic materials capable of concurrently repairing both chemical damage and microstructural defects remains a formidable challenge. Furthermore, the repair mechanisms employed in existing microstructurally repairable superhydrophobic materials often compromise their heat resistance and chemical durability, thereby limiting their applicability in harsh environments. Herein, we propose a bio-based durable superhydrophobic composite coating with dual repairability for surface chemistry and microstructure. Furan-functionalized heterogeneous cellulose nanocrystals (FHCC) and maleimide-functionalized polydimethylsiloxane (MPDMS) were synthesized and crosslinked to form the FHCC-MPDMS coating via Diels-Alder (DA) cycloaddition reaction. Subsequent 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (PFDTS) modification yielded the superhydrophobic F-FHCC-MPDMS coating with a WCA of 157o. DA covalent network endowed the coating with exceptional chemical stability against temperature, solvents, and acid/base. Importantly, the plasma-etched F-FHCC-MPDMS coating (superhydrophilicity with a WCA of 0o) was fully restored through thermal-driven rotation and rearrangement of MPDMS and PFDTS. Moreover, the retro-DA reaction triggered by both solvent and heat enabled localized MPDMS dissolution, regenerating hierarchical micro/nanostructures after abrasion damage and thereby efficiently recovering superhydrophobicity upon tetrahydrofuran immersion. This work demonstrates a bio-derived superhydrophobic coating with dual self-repair capability, offering a promising solution for durable applications in harsh environments.