Non-Fluorinated, Superhydrophobic Binder-Filler Coatings on Smooth Surfaces: Controlled Phase Separation of Particles to Enhance Mechanical Durability

Abstract

There has been a recent drive to develop nonfluorinated superhydrophobic coatings due to the toxicity, cost, and environmental impact of perfluorinated components. One of the main challenges in developing superhydrophobic coatings in general and non-fluorinated superhydrophobic coatings in particular is optimization of mechanical durability, as the rough asperities required for maintaining superhydrophobicity tend to be easily removed by abrasion. Although rough and self-similar hydrophobic surfaces composed of loosely adhered particles or highly porous structures tend to produce excellent superhydrophobicity, they have low inherent mechanical durability and their longevity under real conditions is compromised. To address this issue, this work investigates the addition of a polymeric matrix material (the binder) to hydrophobic nanoparticles (the filler) to produce spray-coated superhydrophobic surfaces with improved inherent mechanical durability. Hansen solubility parameters were used to tune the interactions between the binder, filler, and solvent used to deliver the coating. It was found that lowering the binder/filler miscibility and using a poor solvent mixture generates more surface roughness, thereby lowering the minimum filler load required to achieve superhydrophobicity. This leads to an overall more inherently durable system that remains hydrophobic for thousands of light abrasion cycles.

Superhydrophobic Polymer Composite Surfaces Developed via Photopolymerization

“…Besides pattern generation, photopolymerization also induces phase separation of NPs toward the surface. This phenomenon has previously been reported using silicon NPs, 25 semiconductor nanocrystals, 28 silver decanoate, 29 silica NPs, 30 polymer blends, 31−33 and polymer−solvent systems. 9,15 Figure 1b also shows a magnified view of a single bump, indicating the expected outward movement of NPs from the polymer-rich regions to monomerrich regions (namely upward to the surface) owing to PIPS, which is key to good surface coverage.…”

Self-Healing of Biocompatible Superhydrophobic Coatings: The Interplay of the Size and Loading of Particles

“…The effect of the number of NPs and hydrophobic molecules used to prepare superhydrophobic coatings on the wetting properties is well-documented. ,− To examine this effect, we prepared superhydrophobic coatings using 0.4 g of carnauba wax and 0.1–0.4 g of hydrophilic SiO 2 NPs. Figure presents the wetting properties as a function of the weight ratio of SiO 2 NPs to carnauba wax.…”

Preparation of Stable Superhydrophobic Coatings on Complex‐Shaped Substrates

“…This is to regulate the surface texture and chemical composition of the coatings by changing the nonsolvent fraction and binder content. [37][38][39] The FD-silica/PSI coating with both good superhydrophobicity and mechanical stability was obtained when FD-silica/PSI = 1.54/1.44 and butyl acetate/ ethanol = 6.56/3.85.…”