Multifunctional Hard Yet Flexible Coatings Fabricated Using a Universal Step-by-Step Strategy

Fabrication of Stable Liquid-like Wetting Buckled Surfaces as Bioinspired Antibiofouling Coatings by Using Silicon-Containing Block Copolymers

Inspired by animals with a slippery epidermis, durable slippery antibiofouling coatings with liquid-like wetting buckled surfaces are successfully constructed in this study by combining dynamic-interfacial-release-induced buckling with self-assembled silicon-containing diblock copolymer (diBCP). The core diBCP material is polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS). Because silicon-containing polymers with intrinsic characters of low surface energy, they easily flow over and cover a surface after it has undergone controlled thermal treatment, generating a slippery wetting layer on which can eliminate polar interactions with biomolecules. Additionally, microbuckled patterns result in curved surfaces, which offer fewer points at which organisms can attach to the surface. Different from traditional slippery liquid-infused porous surfaces, the proposed liquid-like PDMS wetting layer, chemically bonded with PS, is stable and slippery but does not flow away. PS-b-PDMS diBCPs with various PDMS volume fractions are studied to compare the influence of PDMS segment length on antibiofouling performance. The surface characteristics of the diBCPs─ease of processing, transparency, and antibiofouling, anti-icing, and self-cleaning abilities─are examined under various conditions. Being able to fabricate ecofriendly silicon-based lubricant layers without needing to use fluorinated compounds and costly material precursors is an advantage in industrial practice.

Solvent-Free and UV-Cured Epoxy Silicone Coating with Excellent Wear Resistance and Antismudge Properties

Transparent, hard, and flexible multifunctional coatings have a wide range of applications; however, most of them need organic solvents. Here, we present a solvent-free and UV-cured coating made from fluorinated epoxy MTQ silicone resin combined with branched triepoxy siloxane as the reactive diluent. After UV-initiated ring-opening polymerization in the presence of a triarylsulfonium hexafluoroantimonate catalyst, the resultant cured coating exhibits high transparency (∼92%, 550 nm), pencil hardness (7H), and flexibility (1 mm bending diameter) due to the formed organic-inorganic nanostructures in a highly cross-linked network. The triepoxy siloxane significantly reduces the viscosity before curing and increases cross-link density of the coating. The coating without any volatile content shows a smooth surface with low roughness (Rq = 0.46 nm) and delivers an anti-smudge ability owing to perfluorinated chains inherited from the MTQ resin. Furthermore, even after 3000 abrasion cycles, the coating still has a water contact angle greater than 90°, displaying excellent wear resistance. Our work provides a promising way to access high-performance multifunctional coatings in a more sustainable manner.

NIR-Driven Self-Healing Phase-Change Solid Slippery Surface with Stability and Promising Antifouling and Anticorrosion Properties

Slippery liquid-infused porous surfaces (SLIPSs) have great potential to replace traditional antifouling coatings due to their efficient, green, and broad-spectrum antifouling performance. However, the lubricant dissipation problem of SLIPS severely restricts its further development and application, and the robust SLIPS continues to be extremely challenging. Here, a composite phase-change lubricant layer consisting of paraffin, silicone oil, and MXene is designed to readily construct a stable and NIR-responsive self-healing phase-change solid slippery surface (PCSSS). Collective results showed that PCSSS could rapidly achieve phase-change transformation and complete self-healing under NIR irradiation and keep stable after high-speed water flushing, centrifugation, and ultrasonic treatment. The antifouling performance of PCSSS evaluated by protein, bacteria, and algae antiadhesion tests demonstrated the adhesion inhibition rate was as high as 99.99%. Moreover, the EIS and potentiodynamic polarization experiments indicated that PCSSS had stable and exceptional corrosion resistance (|Z|0.01Hz = 3.87 × 108 Ω·cm2) and could effectively inhibit microbiologically influenced corrosion. The 90 day actual marine test reveals that PCSSS has remarkable antifouling performance. Therefore, PCSSS presents a novel, facile, and effective strategy to construct a slippery surface with the prospect of facilitating its application in marine antifouling and corrosion protection.

Intelligent anti-impact elastomers by precisely tailoring the topology of modular polymer networks

High-performance elastomers are essential in daily life and various industrial sectors such as personal protection, soft electronics, and vibration control. Nevertheless, despite massive efforts, concurrently achieving ultrahigh flexibility and remarkable impact resistance continues to be elusive. Herein, we report an innovative modular construction strategy that employs a topology-tailoring polymer network consisting of stereoscopic (epoxy-oligosiloxane nanoclusters) and linear (amino-terminated polyurea) building blocks as independent modules to develop intelligent anti-impact elastomers via an epoxy-amine mechanism. By precisely tailoring the topology of building blocks, the elastomers demonstrate high flexibility and toughness, remarkable impact responsiveness and ultrahigh energy dissipation. Their anti-impact ability surpasses those of most common soft and rigid materials such as steel, plastic, rubber, foam, or even polyborosiloxane. Moreover, the elastomers are well-qualified for use in flexible display technologies, owing to their high transparency (>92% transmittance), exceptional fold-resistance (no creasing after 10 000 bends), and good thermal stability (no discoloration at 100 °C). Furthermore, the elastomers exhibit excellent versatility, enabling them to be combined with either soft or rigid materials to generate composites with ultrahigh puncture and ballistic resistance. This study offers a promising framework for the design and fabrication of intelligent anti-impact elastomers and provides valuable insights into the development of next-generation protective materials.

High-Performance Polyurea Improved by Reactive Nanocluster for Antibiofouling

Polyurea has found applications in protective coatings. Yet, the too fast polymerization and lack of functions limit its application. Herein, we report a high-performance polyurea via the stepwise polymerization of an isocyanate (NCO)-terminated prepolymer consisting of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) (PPG-b-PEG-b-PPG) with a nanocluster synthesized via the hydrolysis of N-phenylaminomethyltriethoxysilane. Such a nanocluster contains low-reactivity secondary amines, so the polymerization of polyurea can be slowed down (over 1 h), which improves its wetting and adhesion to a substrate. The residual silanol groups on the nanocluster further increase the adhesion. Such polyurea exhibits high adhesion on various substrates, including glass, ceramic, steel, copper, titanium, wood, and natural rubber (∼2.35-14.64 MPa). Besides, the nanoclusters can cross-link the prepolymer into a tough network, endowing the polyurea with a high mechanical strength of ∼25 MPa, much higher than the traditional polyaspartic ester polyurea. On the other hand, the PEG segments enable the polyurea to have good fouling resistance against proteins (fibrinogen absorption was reduced by over 90%), bacteria (RBA of S. aureusE. coli and Pseudomonas sp. was less than 10%), as well as diatom (diatom density was less than 100 cells/mm2). The polyurea is expected to find applications in biomedical engineering and marine antifouling.

Slippery Porous-Liquid-Infused Porous Surface (SPIPS) with On-Demand Responsive Switching between "Defensive" and "Offensive" Antifouling Modes

Slippery liquid-infused porous surfaces (SLIPS) have received widespread attention in the antifouling field. However, the reduction in antifouling performance caused by lubricant loss limits their application in marine antifouling. Herein, inspired by the skin of a poison dart frog which contains venom glands and mucus, a porous liquid (PL) based on ZIF-8 is prepared as a lubricant and injected into a silicone polyurethane (SPU) matrix to construct a new type of SLIPS for marine antifouling applications: the slippery porous-liquid-infused porous surface (SPIPS). The SPIPS consists of a responsive antifoulant-releasing switch between "defensive" and "offensive" antifouling modes to intelligently enhance the antifouling effect after lubricant loss. The SPIPS can adjust antifouling performance to meet the antifouling requirements under different light conditions. The wastage of antifoulants is reduced, thereby effectively maintaining the durability and service life of SLIPS materials. The SPIPS exhibits efficient lubricant self-replenishment, self-cleaning, anti-protein, anti-bacterial, anti-algal, and self-healing (97.48%) properties. Furthermore, it shows satisfactory 360-day antifouling performance in actual marine fields during boom seasons, demonstrating the longest antifouling lifespan in the field tests of reported SLIPS coatings. Hence, the SPIPS can effectively promote the development of SLIPS for neritic antifouling.

Fabrication of Robust Carbon Dots Containing Coatings with UV-Shielding, Light Conversion, and Antifogging Multiple Functions

Although a wide variety of single-function coatings have been successfully developed, the integration of multiple functions onto a single coating has remained an immense challenge in the field. Here, we report a simple room-temperature fabrication of robust coatings with UV-shielding, light conversion, and antifogging functionalities. The addition of glutaraldehyde (GA) molecular cross-linker and carbon dot (CD) nanocross-linker with light conversion function to poly(vinyl alcohol) (PVA) resulted in the formation of robust spatial structures of coatings. The fluorescence intensity tests demonstrated that the coatings had an excellent ability to absorb and convert ultraviolet light into blue-violet light. Both cold-warm and hot-vapor tests showed that the coatings had excellent antifogging performance. To our surprise, no creases were observed after coatings were immersed in water for 1 month, indicating that these are much stronger than those reported so far. The 8H pencil hardness and wear resistance attested to their excellent mechanical properties. The current preparation method can be operated at ambient temperature and is not restricted by the substrate type and shape. Therefore, it may also expand the possibilities for future applications of coatings for glass windows, optical microscopes, eyeglasses, agricultural greenhouses, and so on.

Innovative Solid Slippery Coating: Uniting Mechanical Durability, Optical Transparency, Anti-Icing, and Anti-Graffiti Traits

Slippery coatings, such as the slippery liquid-infused porous surface (SLIPS), have gained significant attention for their potential applications in anti-icing and anti-fouling. However, they lack durability when subjected to mechanical impact. In this study, we have developed a robust slippery coating by blending polyurethane acrylate (PUA) with methyltriethoxysilane (MTES) and perfluoropolyether (PFPE) in the solvent of butyl acetate. The resulting mixture is homogeneous and allows for uniform coating on various substrates using a drop coating process followed by drying at 160 °C for 3 h. The cured coating exhibits excellent water repellency (contact angle of ~108° and sliding angle of ~8°), high transparency (average visible transmittance of ~90%), exceptional adherence to the substrate (5B rating according to ASTMD 3359), and remarkable hardness (4H on the pencil hardness scale). Moreover, the coating is quite flexible and can be folded without affecting its wettability. The robustness of the coating is evident in its ability to maintain a sliding angle below 25° even when subjected to abrasion, water jetting, high temperature, and UV irradiation. Due to its excellent nonwetting properties, the coating can be employed in anti-icing, anti-graffiti, and anti-sticking applications. It effectively reduces ice adhesion on aluminum substrates from approximately 217 kPa to 12 kPa. Even after 20 cycles of icing and de-icing, there is only a slight increase in ice adhesion, stabilizing at 40 kPa. The coating can resist graffiti for up to 400 cycles of writing with an oily marker pen and erasing with a tissue. Additionally, the coating allows for easy removal of 3M tape thereon without leaving any residue.

A strain-reinforcing elastomer adhesive with superior adhesive strength and toughness

Strong and ductile adhesives often undergo both interfacial and cohesive failure during the debonding process. Herein, we report a rare self-reinforcing polyurethane adhesive that shows the different phenomenon of only interfacial failure yet still exhibiting superior adhesive strength and toughness. It is synthesized by designing a hanging adhesive moiety, hierarchical H-bond moieties, and a crystallizable soft segment into one macromolecular polyurethane. The former hanging adhesive moiety allows the hot-melt adhesive to effectively associate with the target substrate, providing sufficient adhesion energy; the latter hierarchical H-bond moieties and a crystallizable soft segment cooperate to enable the adhesive to undergo large lap-shear deformations through sacrificing weak bonds and mechano-responsive strength through the fundamental mechanism of strain-induced crystallization. As a result, this polyurethane adhesive can keep itself intact during the debonding process while still withstanding a high lap-shear strength and dissipating tremendous stress energy. Its adhesive strength and work of debonding are as high as 11.37 MPa and 10.32 kN m-1, respectively, outperforming most reported tough adhesives. This self-reinforcing adhesive is regarded as a new member of the family of strong and ductile adhesives, which will provide innovative chemical and structural inspirations for future conveniently detachable yet high-performance adhesives.

Transparent superhydrophilic composite coating with anti-fogging and self-cleaning properties

Superhydrophilic coatings have incomparable advantages in anti-fogging and self-cleaning but are limited to poor abrasion resistance and water resistance. Consequently, the research on the contradiction between hydrophilicity and water resistance, as well as abrasion resistance and visible transmittance, has become a focus of superhydrophilic coatings. Herein, we design a ceramic-polymer superhydrophilic composite coating with a high density, strong cross-linking structure, and smooth surface. Because of its static water contact angle (WCA = 3.2°) and short water spreading time (ST = 1878 ms), the transparent composite coating exhibits anti-fogging performance. Meanwhile, it exhibits anti-fogging durability even after 400 Taber abrasion cycles under a 250 g load or immersion in boiling water for 30 min. Furthermore, the result of self-cleaning characterization and theoretical analysis demonstrate that the low surface roughness endows the composite coating with excellent self-cleaning properties. The composite coating can effectively scavenge oil and dust pollution on its surface in a humid environment. Thus, the developed composite coating in this work is potential in the anti-fogging and self-cleaning fields.

Progress in Polymer-Ceramic Hybrid Antifouling Coatings

Simultaneous realization of superior mechanical and antifouling properties is critical for a coating. The use of stereoscopic polysiloxanes in place of linear polysiloxanes to fabricate antifouling coatings can combine properties of organic and inorganic materials, i.e., they can exhibit both high hardness and wear resistance from inorganic components as well as the flexibility and tunability from organic components. This strategy is used to prepare hard yet flexible antifouling coatings or polymer-ceramic hybrid antifouling coatings. In this mini-review, we report the recent advances in this field. Particularly, the effects of stereoscopic polysiloxane structures on their mechanical and antifouling properties are discussed in detail.

Non-isocyanate Polyurethane Coating with High Hardness, Superior Flexibility, and Strong Substrate Adhesion

Flexible hard coatings with strong adhesion are critical requirements for several foldable devices and marine applications; however, only a few such coatings have been reported. Herein, we report a non-isocyanate polyurethane (NIPU) coating prepared by the epoxy-oligosiloxane nanocluster-amine curing reaction and cyclic carbonate-amine polyaddition, where the former provides the coating with ceramic-like hardness and polymer-like flexibility while the latter polymerization results in NIPU with strong substrate adhesion. The coating is transparent (>92% transmittance), hard (5-7 H), and flexible (2 mm bending diameter). It has strong adhesion to various substrates including aluminum alloy, titanium, steel, glass, ceramic, epoxy, and polyethylene terephthalate (2-8 MPa), which can be attributed to the high density of polar groups in NIPU. Moreover, we can facilely endow the coating with anti-icing, self-cleaning, and anti-smudge capabilities by incorporating amine-terminated low-surface-tension polydimethylsiloxane (PDMS) to replace a part of the amine curing agent. Particularly, the mechanical properties of NIPU coatings are only slightly affected by the introduction of low-content PDMS since it intends to enrich on the surface. The novel coating has promising future for use in fields of foldable devices and marine applications.