Durable superhydrophobic/highly oleophobic coatings from multi-dome SiO₂ nanoparticles and fluoroacrylate block copolymers on flat substrates

Herein, we focus on the creation of durable superhydrophobic and highly oleophobic coating through the casting of multi-dome hydrophobic SiO₂ nanoparticles (NPs) modified with fluoroalkylsilane onto a glass plate, followed by coating the surface of pre-stacked particles with another layer of poly(methyl methacrylate)-b-poly(dodecafluoroheptyl methacrylate; PMMA-b-PDFHM). The novel multi-dome hydrophobic SiO₂ NPs had re-entrant surfaces covered by methacryloxy groups, which were facilely prepared via a reaction of pristine SiO₂ NPs with γ-methacryloxypropyltrimethoxysilane (MPTMS) using an in situ alkali-catalyzed sol-gel process in an n-propanol (NPA) solution. Fluoroalkylsilane-modified SiO₂ NPs were prepared by the in situ hydrolysis of 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (FDTES) in a THF-H₂C₂O₄ (aq.) suspension of multi-dome hydrophobic SiO₂ NPs. It was found that a decrease in the content of hydrolyzed-condensed FDTES contributed to the reduction in conglutination and the aggregation of multi-dome hydrophobic SiO₂ NPs in the obtained coating layer, leading to a relatively loose surface structure with gaps or cavities. In this case, the coating surface supported the Cassie-Wenzel transition state with hexadecane and thus exhibited high oleophobicity with high adhesion. Moreover, superhydrophobicity with water droplets adopting a low-adhesive bouncing Cassie mode was achieved. More importantly, the coating was still well adhered to the glass substrate and demonstrated high oleophobicity and superhydrophobicity after it was subjected to scouring tests using strong base and acid aqueous solutions.