Seawater-responsive SiO2 nanoparticles for in situ generation of zwitterionic polydimethylsiloxane antifouling coatings with underwater superoleophobicity

Marine fouling that is caused by oily and biological pollutants is an urgent issue globally. To improve the static antifouling (AF) performance of polydimethylsiloxane (PDMS) coatings, a strategy of zwitterionic group introduction has been proposed. Two new analogues of seawater-responsive silanes, (N-methoxyacylethyl)-3-aminopropyltriethoxysilane (MAPS) and bis(N-methoxyacylethyl)-3-aminopropyltriethoxysilane (BMAPS) were synthesized by aza-Michael addition with cost-efficient agents, and grafted onto SiO2 nanoparticles by silanization to achieve modified-SiO2 (M-SiO2 and BM-SiO2). The modified-SiO2 was embedded into PDMS to construct biomimetic heteroarchitecture coatings that could transform from superhydrophobicity in air to underwater superoleophobicity. The coatings could self-regenerate underwater superoleophobicity after mechanical abrasion. The hierarchical structure and oil tolerance can be maintained after field-exposure trials or five months of immersion in artificial seawater. The synergy of the hydrated barrier layers and the intrinsic nature of the zwitterions that gave rise to the AF capability of the PDMS/modified-SiO2 coatings was demonstrated by laboratory assays and marine field trials. Little difference existed between the M-SiO2- and BM-SiO2-based coatings. The PDMS/modified-SiO2 coatings with a comprehensive durability and AF capability show potential for application in practical marine fouling, and provide options for other superwettable applications.