Organic superhydrophobic coatings with mechanical and chemical robustness
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Research Letter
Organic superhydrophobic coatings with mechanical and chemical robustness Sajia Afrin and David Fox, NanoScience Technology Center, University of Central Florida, Orlando, FL, USA; Department of Chemistry, University of Central Florida, Orlando, FL, USA Lei Zhai , NanoScience Technology Center, University of Central Florida, Orlando, FL, USA; Department of Chemistry, University of Central Florida, Orlando, FL, USA; Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, USA Address all correspondence to Lei Zhai at [email protected] (Received 8 April 2020; accepted 24 April 2020)
Abstract Stable superhydrophobic coatings were produced from aqueous suspensions of epoxy nanoparticles. The superhydrophobic coatings demonstrated excellent mechanical robustness and chemical resistance. Aqueous solutions of ionic surfactants, nonionic surfactants, and small organic molecules on superhydrophobic coatings could wet the superhydrophobic coatings. However, the superhydrophobicity can be recovered by rinsing the wet surface with water. It was also discovered that, although seemed wetted, the superhydrophobic surface was separated from the solution of ionic surfactant by a layer of ionic surfactant molecules. In contrast, nonionic and small organic molecules could not aggregate on the superhydrophobic surfaces; the coatings were exposed to the solutions.
Introduction Superhydrophobic surfaces in nature are generated from micro-/nanostructures of hydrophobic components as demonstrated in lotus leaves, butterfly wings, rice leaves, mosquito eyes, red rose petals, etc.[1,2] A superhydrophobic surface has a water contact angle larger than 150° and a hysteresis of less than 5°.[3] Synthetic mimicry of natural structures has been achieved through different approaches,[4] including sol–gel,[5] gradient process,[6] surface roughness enhanced through corrosion,[7] self-assembly,[8] electrospinning,[9] spraying,[10,11] nanoparticle assembly,[12] and phase separation.[13] These artificial superhydrophobic coatings have demonstrated promising applications for self-cleaning,[14] anti-icing,[15] oil/water separation,[16,17] corrosion protection,[18] etc. On the other hand, the practical application of superhydrophobic coatings requires both chemical and mechanical stability. Inorganic nanostructures provide strong mechanical robustness but poor chemical stability against the harsh chemical environment.[19] Organic coatings offer good chemical stability, however exhibit limited mechanical robustness and durability.[20] The roughness required by superhydrophobic surfaces is obtained by generating porous coatings that are not mechanically stable. Tiwari and coworker recently reported a fabrication of all-organic superhydrophobic coatings with mechanochemical robustness using epoxy to bind polytetrafluoroethylene (PTFE) nanoparticles.[19] In this article, a simple and cost-effective one-pot method was developed to prepare superhydrophobic coatings from aqueous suspensions of epoxy nanoparticles sy
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