Robust superamphiphobic coatings based on silica particles bearing bifunctional random copolymers

Fabrication of Durable, Chemically Stable, Self-Healing Superhydrophobic Fabrics Utilizing Gellable Fluorinated Block Copolymer for Multifunctional Applications

Limited durability and complex materials restrict the application of superhydrophobic fabrics in daily life. In this work, gellable fluorinated block copolymer poly(dodecafluoroheptyl methacrylate)-block-poly(3-(triethoxysilyl)propyl methacrylate) (PDFMA-b-PTEPM) was used to fabricate adhesive-free superhydrophobic poly(ethylene terephthalate) (PET) fabrics via a simple dip-coating technology and sol-gel reaction. The growth of silica nanoparticles builds up a rough hierarchical structure and provides sol-gel reaction sites of PTEPM segments. The grafting of block copolymer significantly reduced the surface free energy of the fabrics, resulting in an excellent superhydrophobicity with a water contact angle of 160.2°. Benefiting from extensive chemical bond grafting and cross-linking of the PTEPM segment, the fabric exhibits excellent durability in mechanical abrasion, chemical treatment, and washing. The coating has withstood 50 sandpaper abrasion cycles and 400 soft friction cycles and can maintain superhydrophobic properties in various solvents, freezing and a wide pH range. These superhydrophobic fabrics with a long life span possess self-cleaning, anti-icing, oil-water separation, and self-healing capabilities. The multifunctional fabrics developed in this study are durable and easy to produce, possessing the potential for applications in industry and daily life.

Design of robust superamphiphobic surfaces with enlarged area fractions: the considerable role of Laplace pressure in dynamics of contact lines

Superamphiphobic surfaces have attracted widespread attention because of their great potential for applications in biotechnology, optoelectronics, water/oil separation, etc. Re-entrant curvatures are widely reported to provide a metastable Cassie state for superamphiphobicity. For high contact angles, re-entrant surfaces with a small area fraction (f) are designed according to the Cassie equation. However, this will make the surfaces take high local pressures under a mechanical force and thus suffer from frangibility. Robustness and high repellency are seemingly mutually exclusive. Herein, contrary to Cassie's equation, we show that high contact angles (>150°) with a large f (69.4%) of water and oleic acid can be achieved by utilizing a large upward Laplace pressure with narrow and parallel channel geometries. We deeply studied the effect of Laplace pressure on superamphiphobicity and suppose that the larger upward Laplace pressure stops the droplet earlier and pins the contact line at a higher position, providing a higher contact angle. The similar effect of viscous force well supports our explanation. These findings enable us to obtain robust and durable superamphiphobic surfaces with an enlarged area fraction and simple re-entrant microstructures. Our work may open up design strategies for robust superamphiphobic surfaces with practical applications.

Short-chain fluorocarbon-based polymeric coating with excellent nonwetting ability against chemical warfare agents

The ongoing concerns and regulations on long-chain fluorinated compounds (C8 or higher) for nonwetting coatings have driven the market to search for sustainable alternative chemistries. In this study, a copolymeric coating containing short-chain fluorinated groups was synthesized to achieve excellent nonwetting ability against hazardous chemical warfare agents (CWAs). A copolymer of 1H,1H,2H,2H-perfluorooctyl methacrylate (PFOMA) and ethylene glycol dimethacrylate (EGDMA, crosslinker) was directly coated onto a textile fabric via initiated chemical vapor deposition. The p(PFOMA-co-EGDMA) coating shows a rough-textured morphology with a bumpy, raspberry-like structure leading to high contact angles (θ water > 150° and θ dodecane = 113.8°) and a small water shedding angle (<5°). Moreover, the p(PFOMA-co-EGDMA) coating was further analysed for application in military fabrics: air permeability, tensile strength, and safety against toxic perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Outstanding nonwetting was noticeably achieved against different CWAs, including bis(2-chloroethyl)sulfide (HD), pinacolyl methylfluorophosphonate (GD), and O-ethyl S-(2-diisopropylaminoethyl)methylphosphonothioate (VX) (θ HD = 119.1°, θ GD = 117.0°, and θ VX = 104.1°). The coating retained its nano-structuration and nonwetting ability for water and n-dodecane despite being subjected to 250 cycles of Martindale abrasion and harsh chemicals (NaOH and HCl). The robustness and scalable straightforward preparation route of the coating make it an ideal approach for designing durable next-generation CWA nonwetting coatings for fabrics with favorable health and environmental properties.

Photoredox Catalysis for the Fabrication of Water-Repellent Surfaces with Application for Oil/Water Separation

Silanization processes with perfluoroalkyl silanes have been demonstrated to be effective in developing advanced materials with many functional properties, including hydrophobicity, water repellency, and self-cleaning properties. However, practical industrial applications of perfluoroalkyl silanes are limited by their extremely high cost. On the basis of our recent work on photoredox catalysis for amidation with perfluoroalkyl iodides, its application for surface chemical modification on filter paper, as an illustrative example, has been developed and evaluated. Before photocatalytic amidation, the surface is functionalized with amine functional groups by silanization with 3-(trimethoxysilyl)propylamine. All chemically modified surfaces have been fully characterized by attenuated total reflection infrared (ATR-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and three-dimensional (3D) profiling to confirm the successful silanization and photocatalytic amidation. After surface modification of the filter papers with perfluoroalkanamide, they show high water repellency and hydrophobicity with contact angles over 120°. These filter papers possess high wetting selectivity, which can be used to effectively separate the organic and aqueous biphasic mixtures. The perfluoroalkanamide-modified filter papers can be used for separating organic/aqueous biphasic mixtures over many cycles without lowering the separating efficiency, indicating their reusability and excellent durability.

Super-robust superamphiphobic surface with anti-icing property

Compared with superhydrophobic surfaces, superamphiphobic surfaces have a wider commercially availability. However, the initially fragile nature of micro or nano-structures hinders the large-scale applications of superamphiphobic surfaces. In this work, we report free-standing monoliths with durable superamphiphobic properties not only in the outer layer surfaces but also extending throughout the whole volume, which will demonstrate permanent superamphiphobicity. The monolith surface can repel a series of organic solutions with a surface tension as low as 36.4 mN m-1, and display good self-cleaning effect toward to blood or viscous mud. In addition, the monolith can maintain the superhydrophobicity no matter whether facing corrosive solution attack or mechanical abrasion, indicating the excellent chemical and mechanical properties. The monolith surfaces also display delayed-icing property and easy de-icing process.

A scalable, self-healing and hot liquid repelling superamphiphobic spray coating with remarkable mechanochemical robustness for real-life applications

A simultaneous demonstration of scalability, mechanochemical robustness, self-healing and hot liquid repelling features is still a major challenge in fabricating superamphiphobic coatings. In this work, we developed a facile and effective silica-inorganic adhesive-based spray coating for the preparation of self-healing and hot liquid repelling superamphiphobic coatings that demonstrate good mechanical durability (under repeated adhesive tape-peeling tests, ultrasonic treatment, sandpaper abrasion and sand flow impact tests) and superstrong chemical robustness when exposed to highly corrosive media, such as 98% sulfuric acid and 5% chromic acid, for a long time. In addition, our superamphiphobic paints can be coated on large-sized substrates to create large robust coatings for real-world applications, which are still regarded as the tightest bottlenecks in the development of superamphiphobic materials. The large coatings also showed excellent liquid repellence when placed for a long time in the outdoor environment, and upon repeatable quartz sand abrasion and treading stepping test cycles. Moreover, the anti-smudge ability, semitransparency, repeated self-healing ability, self-cleaning behaviour both in air and oil, and hot liquid repelling behavior of the resultant coatings are also investigated. Taking multifaceted stability and scalability into consideration, our described coatings are promising for more vital applications such as windows, infrastructures, crude oil pipelines, in harsh chemical engineering, etc.

Sequentially Reinforced Additive Coating for Transparent and Durable Superhydrophobic Glass

Now that there are various routes to prepare superhydrophobic surfaces for self-cleaning, anti-icing, liquid collecting, etc., attentions are moving toward low-cost upscaling of routes and increasing the reliability for actual applications. However, the required micro-nano structures for superhydrophobicity are light scattering and very vulnerable to abrasion. This intrinsically conflicts with the transparency and durability of superhydrophobic glass, which are the major barriers for its commercialization. In this study, we present a novel sequentially reinforced additive coating (SRAC) process to realize robust and transparent micro-nano structured film with tough intergranular sintering. A benign aqueous-based ink with poly(furfuryl alcohol) (PFA) and silica species is carefully designed and sprayed on glass to enable self-phase separation and morphology construction. The coatings reach the static contact angle (SCA) for water over 166° and withstand a 6H pencil scratching, the cross-cut test, and sand abrasion. Moreover, we also performed a 90 day outdoor performance test and the glass maintained superhydrophobicity with an SCA of 154°. These results provide a low-cost waterborne ink formula, and the high throughput and upscalable SRAC process could be a convenient technology for the fabrication of large area, robust superhydrophobic coatings.

Silicone-Infused Antismudge Nanocoatings

A polyurethane-based NP-GLIDE coating that bears on its surface and in its interior nano-pools of a grafted liquid ingredient for dewetting enablement is obtained from casting and curing a film comprising a triisocyanate, a polyol (P1), and a graft (g) copolymer of P1 and poly(dimethylsiloxane) (P1-g-PDMS). A silicone-infused NP-GLIDE (SINP-GLIDE) PU coating is obtained from cocasting the NP-GLIDE precursors with a free silicone oil (SO) or SO mixture (SOs). This paper reports the preparation of the novel SINP-GLIDE coatings and discusses the effect of changing the amount and type of the infused SO as well as the coating formation conditions on their optical clarity. Also reported are the contact and sliding angles of various test liquids on the NP-GLIDE and SINP-GLIDE coatings, and the data variation trends are rationalized using existing theories. Further, the stable water sliding performance of the SINP-GLIDE coatings under simulated raining and other conditions is demonstrated. The improved and stable water sliding performance of the SINP-GLIDE coatings facilitates their practical applications.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

A free-standing porous silicon-type gel sponge with superhydrophobicity and oleophobicity

Porous and spongy superhydrophobic silicon-type gels monoliths have been fabricated by a facile method.

Omniphobic Polyvinylidene Fluoride (PVDF) Membrane for Desalination of Shale Gas Produced Water by Membrane Distillation

Microporous membranes fabricated from hydrophobic polymers such as polyvinylidene fluoride (PVDF) have been widely used for membrane distillation (MD). However, hydrophobic MD membranes are prone to wetting by low surface tension substances, thereby limiting their use in treating challenging industrial wastewaters, such as shale gas produced water. In this study, we present a facile and scalable approach for the fabrication of omniphobic polyvinylidene fluoride (PVDF) membranes that repel both water and oil. Positive surface charge was imparted to an alkaline-treated PVDF membrane by aminosilane functionalization, which enabled irreversible binding of negatively charged silica nanoparticles (SiNPs) to the membrane through electrostatic attraction. The membrane with grafted SiNPs was then coated with fluoroalkylsilane (perfluorodecyltrichlorosilane) to lower the membrane surface energy. Results from contact angle measurements with mineral oil and surfactant solution demonstrated that overlaying SiNPs with ultralow surface energy significantly enhanced the wetting resistance of the membrane against low surface tension liquids. We also evaluated desalination performance of the modified membrane in direct contact membrane distillation with a synthetic wastewater containing surfactant (sodium dodecyl sulfate) and mineral oil, as well as with shale gas produced water. The omniphobic membrane exhibited a stable MD performance, demonstrating its potential application for desalination of challenging industrial wastewaters containing diverse low surface tension contaminants.

One-step solvothermal deposition of ZnO nanorod arrays on a wood surface for robust superamphiphobic performance and superior ultraviolet resistance

In the present paper, uniformly large-scale wurtzite-structured ZnO nanorod arrays (ZNAs) were deposited onto a wood surface through a one-step solvothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), and differential thermal analysis (DTA). ZNAs with a diameter of approximately 85 nm and a length of approximately 1.5 μm were chemically bonded onto the wood surface through hydrogen bonds. The superamphiphobic performance and ultraviolet resistance were measured and evaluated by water or oil contact angles (WCA or OCA) and roll-off angles, sand abrasion tests and an artificially accelerated ageing test. The results show that the ZNA-treated wood demonstrates a robust superamphiphobic performance under mechanical impact, corrosive liquids, intermittent and transpositional temperatures, and water spray. Additionally, the as-prepared wood sample shows superior ultraviolet resistance.

A Superamphiphobic Sponge with Mechanical Durability and a Self-Cleaning Effect

A robust superamphiphobic sponge (SA-sponge) is proposed by using a single initiated chemical vapor deposition (i-CVD) process. Poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate) (PFDMA) is deposited on a commercial sponge by the polymerization of fluoroalkyl acrylates during the i-CVD process. This PFDMA is conformally coated onto both the exterior and interior of the sponge structure by a single step of the i-CVD process at nearly room temperature. Due to the inherent porous structure of the sponge and the hydrophobic property of the fluorine-based PFDMA, the demonstrated SA-sponge shows not only superhydrophobicity but also superoleophobicity. Furthermore, the fabricated SA-sponge is robust with regard to physical and chemical damage. The fabricated SA-sponge can be utilized for multi-purpose applications such as gas-permeable liquid separators.

Durable and scalable icephobic surfaces: similarities and distinctions from superhydrophobic surfaces

Formation, adhesion, and accumulation of ice, snow, frost, glaze, rime, or their mixtures can cause severe problems for solar panels, wind turbines, aircrafts, heat pumps, power lines, telecommunication equipment, and submarines. These problems can decrease efficiency in power generation, increase energy consumption, result in mechanical and/or electrical failure, and generate safety hazards. To address these issues, the fundamentals of interfaces between liquids and surfaces at low temperatures have been extensively studied. This has lead to development of so called "icephobic" surfaces, which possess a number of overlapping, yet distinctive, characteristics from superhydrophobic surfaces. Less attention has been given to distinguishing differences between formation and adhesion of ice, snow, glaze, rime, and frost or to developing a clear definition for icephobic, or more correctly pagophobic, surfaces. In this review, we strive to clarify these differences and distinctions, while providing a comprehensive definition of icephobicity. We classify different canonical families of icephobic (pagophobic) surfaces providing a review of those with potential for scalable and robust development.

Fabrication of Robust and Antifouling Superhydrophobic Surfaces via Surface-Initiated Atom Transfer Radical Polymerization

Superhydrophobic surfaces were fabricated via surface-initiated atom transfer radical polymerization of fluorinated methacrylates on poly(ethylene terephthalate) (PET) fabrics. The hydrophobicity of the PET fabric was systematically tunable by controlling the polymerization time. The obtained superhydrophobic fabrics showed excellent chemical robustness even after exposure to different chemicals, such as acid, base, salt, acetone, and toluene. Importantly, the fabrics maintained superhydrophobicity after 2500 abrasion cycles, 100 laundering cycles, and long time exposure to UV irradiation. Also, the surface of the superhydrophobic fabrics showed excellent antifouling properties.

Synthesis and self-assembly of well-defined binary graft copolymer and its use in superhydrophobic cotton fabrics preparation

Schematic illustrations of the self-assembly of BGCs and photographs of superhydrophobic performance.