Antifogging Coatings Research Articles

Amphiphilic Nanoscale Antifog Coatings: Improved Chemical Robustness by Continuous Assembly of Polymers.

Designing effective antifog coatings poses challenges in resisting physical and chemical damage, with persistent susceptibility to decomposition in aggressive environments. As their robustness is dictated by physicochemical structural features, precise control through unique fabrication strategies is crucial. To address this challenge, a novel method for crafting nanoscale antifog films with simultaneous directional growth and cross-linking is presented, utilizing solid-state continuous assembly of polymers via ring-opening metathesis polymerization (ssCAPROMP). A new amphiphilic copolymer (specified as macrocross-linker) is designed by incorporating polydimethylsiloxane, poly(2-(methacryloyloxy)ethyl) trimethylammonium chloride (PMETAC), and polymerizable norbornene (NB) pendant groups, allowing ssCAPROMP to produce antifog films under ambient conditions. This novel approach results in distinctive surface and molecular characteristics. Adjusting water-absorption and nanoscale assembly parameters produced ultra-thin (≤100nm) antifog films with enhanced durability, particularly against strong acidic and alkaline environments, surpassing commercial antifog glasses. Thickness loss analysis against external disturbances further validated the stable surface-tethered chemistries introduced through ssCAPROMP, even with the incorporation of minimal content of cross-linkable NB moieties (5mol%). Additionally, a potential zwitter-wettability mechanism elucidates antifog observations. This work establishes a unique avenue for exploring nanoengineered antifog coatings through facile and robust surface chemistries.

High and long-lasting antifogging performance of silane based hydrophilic polymer coating

The inevitable presence of fog causes a loss of light transmission in optical materials and leads to many unacceptable and serious consequences. A promising strategy for avoiding fog is to modulate the wettability of the material surface and further change the formed way of droplets. Although many works achieved high antifogging coatings, they are lack of the long-lasting antifogging at varied conditions. In this work, a high adhesion strength and persistent antifogging capability hydrophilic coating is obtained by utilizing silane coupling agents containing double bonds such as triethoxyvinylsilane (A151) and 3-(trimethoxysilyl)propyl methacrylate (KH570) with 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and then compositing with poly(vinyl alcohol) (PVA). The coating composed of A151 has a relatively uniform and flat surface structure, due to weaker hydrolysis ability of A151 promoted the smooth condensation speed, compared to KH570. Thanks to the hydrophilic and hydrophobic balance properties of the A151-modulated coating network, the resultant coating exhibits good antifogging performance in the range of 0 °C to 90 °C, which keeps a light transmission of about 85 %. Surprisingly, the coating shows excellent adhesion (350–700 kPa) to the substrate, which is significantly better than other conventional hydrophilic antifogging coatings, and the hydrophilic and hydrophobic modulation capability and the enhanced interfacial adhesion of A151 segments provide the basis of the coating for long-lasting antifogging, which would open up a new way of durable hydrophilic antifogging coatings.

Development of a Biopolymer-Based Anti-Fog Coating with Sealing Properties for Applications in the Food Packaging Sector.

The quest for sustainable and functional food packaging materials has led researchers to explore biopolymers such as pullulan, which has emerged as a notable candidate for its excellent film-forming and anti-fogging properties. This study introduces an innovative anti-fog coating by combining pullulan with poly (acrylic acid sodium salt) to enhance the display of packaged food in high humidity environments without impairing the sealing performance of the packaging material-two critical factors in preserving food quality and consumers' acceptance. The research focused on varying the ratios of pullulan to poly (acrylic acid sodium salt) and investigating the performance of this formulation as an anti-fog coating on bioriented polypropylene (BOPP). Contact angle analysis showed a significant improvement in BOPP wettability after coating deposition, with water contact angle values ranging from ~60° to ~17° for formulations consisting only of poly (acrylic acid sodium salt) (P0) or pullulan (P100), respectively. Furthermore, seal strength evaluations demonstrated acceptable performance, with the optimal formulation (P50) achieving the highest sealing force (~2.7 N/2.5 cm) at higher temperatures (130 °C). These results highlight the exceptional potential of a pullulan-based coating as an alternative to conventional packaging materials, significantly enhancing anti-fogging performance.

A novel poly(2-hydroxyethyl acrylamide) copolymer for the fabrication of transparent antifogging coatings on polycarbonate substrates

Although polycarbonate (PC) is widely used in various applications, its inherent hydrophobicity limits its potential in applications that require high light transmittance due to surface fog caused by changes in temperature or humidity in the environment. This work presents a facile method to fabricate transparent antifogging coatings on PC substrates based on poly(2-hydroxyethyl acrylamide-co-2-aminoethyl methacrylate) (P(HEAA-co-AEMA)), in which the AEMA segments have an amino functional group that can react with the ester group on the surface of the PC substrate to form covalent urethane bonds during the heat curing process, avoiding the problems of coating susceptibility to mechanical damage, ease of peeling, etc. Moreover, HEAA units are employed as hydrophilic groups, providing antifogging performance. These antifogging coatings can be easily obtained by coating P(HEAA-co-AEMA) copolymers on PC substrates at room temperature and then curing them by thermal treatment. These transparent coatings exhibited excellent antifogging and self-cleaning performance. Furthermore, the coatings exhibited good adhesion in the cross-cut test and thermal stability in the hot water resistance test. Therefore, the present P(HEAA-co-AEMA) copolymer coatings are promising for practical antifogging applications.

Design of Abrasion-Resistant, Long-Lasting Antifog Coatings.

Fog formation is a common challenge for numerous applications, such as food packaging, mirrors, building windows, and freezer/refrigerator doors. Most notably, fog forms on the inner surfaces of prescription glasses and safety eyewear (particularly when used with a mask), face shields, and helmet lenses. Fogging is caused by the distortion of light from condensed water droplets present on a surface and can typically be prevented if the surface static water contact angle (θ) is less than ∼40°. Such a low contact angle can be readily achieved by either increasing the substrate surface energy or by engineering surface nanotexture. Unfortunately, such nanotexture can be readily damaged with use, while high surface energy substrates get covered with low surface energy foulants over time. Consequently, even with numerous ephemeral antifog coatings, currently there are no commercially available, durable, and permanent antifog coatings. Here we discuss the development of a new class of high-performance antifog coatings that are abrasion-resistant and long-lasting. These polyvinylpyrrolidone-based coatings, designed based on the classical Ratner-Lancaster wear model, dramatically outperform the base polymer, as well as all tested commercially available antifog coatings. Specifically, these coatings exhibit a > 400% increase in fogging time compared to base polymer, a > 50,000% increase in wear resistance, and excellent long-term antifog performance. The developed coatings also significantly outperformed all tested commercially available antifog coatings in terms of their antifog performance, wear resistance, and long-term cyclical performance. Additionally, the key design strategies employed here─incorporation of toughening agents and hydrophilic slip additives─offer a new approach to developing high-performance, durable antifog coatings based on other well-known antifog polymers.

Anti-fogging surfaces produced by plasma polymerization of acrylic acid

In this paper, plasma enhanced chemical vapor deposition (PECVD) of acrylic acid (AA) was employed as a one-step and solvent-free technique to prepare durable organic anti-fogging coatings on mirror and glass surfaces. The effects of important PECVD parameters including substrate temperature and plasma power on the deposition kinetics, as well as on the structural and morphological properties of the as-deposited films were investigated. Employing a low substrate temperature (5 °C) and a high plasma power (30 W) combination resulted in the highest observed deposition rate of 27.7 nm/min. Fourier-transform infrared (FTIR) spectroscopy showed high structural resemblance between PECVD-PAA and reference poly(acrylic acid) (PAA). The PAA-deposited surfaces showed excellent and durable anti-fogging performance without any loss in their optical transparencies. Successive antifogging tests showed that the PAA thin film exhibited high functional durability without delamination, indicating that it can be used in real-world applications.

Radiation polymerization for the preparation of universal coatings: remarkable anti-fogging and frost-resisting performance.

Hydrophilic anti-fogging coatings have attracted considerable attention due to their ease of preparation and excellent fog resistance. In this study, a hydrophilic anti-fogging coating based on the random copolymer p(AA-co-SAS) was prepared using acrylic acid (AA) and sodium allylsulfonate (SAS) as monomers through radiation polymerization. The introduction of SAS successfully transformed the random copolymer from a gel state into a film-forming polymer solution. The presence of AA structural units in p(AA-co-SAS) improved the film-forming properties of the polymer solution. Additionally, there was a positive correlation between the proportion of SAS structural units in the random copolymer and the scratch hardness and wetting properties of the coating. After coating polycarbonate (PC) sheets, the surface hydrophilicity was significantly enhanced, with the contact angle of PC-AA10/SAS5 decreasing from 100.1° to 18.8° within 50 seconds. The outstanding wetting properties endowed the coating with exceptional anti-fogging and frost-resisting performance. It exhibited optimal transparency under both testing conditions and demonstrated good stability during cyclic testing. Tape adhesion tests indicated that the adhesion between the coating and PC reached a 5B level. When AA10/SAS5 was applied to PET film, glass, and PMMA goggles, all samples showed excellent anti-fog performance. Even after being naturally placed for one year under ambient conditions, the PMMA goggles still maintained good performance in the anti-fog and frost resistance tests. The remarkable comprehensive properties of the polymer coating based on p(AA-co-SAS) suggest enormous potential applications in industries such as packaging, healthcare, and optical equipment.

Rational design and easy fabrication of transparent photothermal/hygroscopic composite coatings with long-lasting antifogging performance under sunlight activation.

Hygroscopic polymers are good candidates for antifogging coatings, but their long-term effectiveness is limited by the equilibrium between water absorption and expansion. As an efficient and environmentally friendly solution, photothermal materials are being introduced into the field of antifogging. However, there is a need for enhancement in the spectral characteristics of most photothermal materials within the visible light region. In addition, photothermal antifogging coatings often exhibit a delay in heating response, which hinders their ability to promptly evaporate condensed water droplets in the absence of illumination or during initial illumination. Here, a bilayer structure design of photothermal nanomaterials/hygroscopic polymers is proposed to achieve long-term antifogging under sunlight activation. Ensuring the rapid absorption of condensed water droplets on the coating surface, while simultaneously achieving efficient photothermal conversion for a swift temperature increase over the entire coating, is key to this approach, which will not only suppress early fogging but also lead to an exponential decrease of the nucleation rate of droplets. During this process, a dynamic equilibrium is gradually established between the condensation and evaporation of fog droplets, leading to long-term antifogging properties. The light transmittance of the composite coatings reaches as high as ca. 75% in the visible light region, making them well suited for a diverse range of transparent substrate and device applications. A clear field of view can be maintained for at least 6 h under 1 sun illumination above 65 °C hot steam. The antifogging/defogging performance is effectively demonstrated even under challenging non-ideal natural conditions, such as low solar irradiation during dusk or when placed indoors behind windows.

Bio‐Templated Silver Nanopatterns for Photothermal and Antifogging Coatings

AbstractTransparent photothermal coatings based on plasmonic noble metals often face a trade‐off between achieved temperatures and transmittances. This challenge arises from the fact that plasmonic nanoparticles (NPs), which rely on their size and structures, selectively absorb light of various wavelengths and convert it into heat. In the cases of randomly arranged plasmonic NPs, absorbances are predominantly in the visible range, leading to lowered transmittances. In this work, the self‐assembly behavior of a biotemplate containing flexible potato virus A (PVA) is used to produce network‐like surface patterns with controllable intermittent vacancies. These templates effectively anchor silver nanoparticles (AgNPs), forming dense arrays of plasmonic hotspots interspersed with vacant regions. With this approach, a temperature increase of 21 °C above ambient temperature under 1‐sun radiation is achieved while maintaining a visible light transmittance as high as 78% measured at 550 nm wavelength. The PVA biotemplated AgNPs show excellent potential as antifogging coating, exhibiting 2–3 times faster defogging rates compared to uncoated samples in both indoor and outdoor conditions. Overall, a platform is presented for biotemplating metal NPs, the development of long‐range surface patterns with controlled vacancies, and the demonstration of transparent photothermal activity with an antifogging application.

Thiol-ene click reaction as an effective tool for the synthesis of PEG-functionalized alkoxysilanes-precursors of anti-fog coatings

The article presents a very simple method of glass modification to obtain the anti-fog effect. Silanes containing two types of functional groups, namely a hydrophilic and polar polyether group and an alkoxysilyl group (to bond with the surface of the modified material) were synthesized in thiol-ene reactions. The hydrothiolation reactions of polyethers containing a C=C terminal bond with mercaptoalkoxysilane proceeded efficiently, yielding quantitatively appropriate products under mild reaction conditions. This method enabled the synthesis of a series of alkoxysilanes functionalized with polyethers, differing in structure. The group of obtained derivatives was characterized by 1H, 13C, 29Si NMR, and FT-IR analyses, and then used to prepare coatings on glass using the sol–gel method. The coated glass surfaces exhibited transparency, superhydrophilic or hydrophilic properties, anti-fog and anti-frost performance.

Robust transparent superhydrophilic antifogging coatings on glass substrates by a facile rapid thermal process

In this study, a rapid thermal process, which can be achieved via the conventional glass tempering process, was utilized to fabricate silica-based superhydrophilic antifogging coatings with micro-nano hierarchical roughness on glass substrates. The effects of SiO2 nanoparticle and triethylborate loadings on the coatings’ properties have been systematically investigated. Moreover, the formation mechanism of such coatings has been explained. The optimal coatings demonstrate a high level of hydrophilicity with a water contact angle (WCA) of ∼ 0°. Meanwhile, such coatings exhibit good antifogging effect and robustness as well.

Transparent lignin nanoparticles for superhydrophilic antifogging coatings and photonic films

Lignin nanoparticles are useful in multiple applications, but their opaqueness remains an obstacle in optical applications. In this study, we present a method to prepare optically clear lignin nanoparticle dispersions from acetylated lignin. Thin lignin nanoparticle films remained transparent when deposited on glass and other smooth surfaces, and monolayered particle films provided effective antifogging properties. The particles could also be used to prepare multilayered films with bright structural colors that could be controlled via the film-thickness and were retained in dry conditions. We also developed an improved energy- and cost-efficient esterification method for controlled and quick lignin acetylation. The reaction could be selectively controlled to acetylate only aliphatic groups or to also include phenolic groups. We show here that stable nanoparticle dispersions can be produced from acetylated lignin at very high initial lignin concentrations without the formation of aggregates. Both the very short reaction time and high possible lignin concentration make the process industrially feasible as shown with a preliminary techno-economic assessment.

Superhydrophilic multifunctional antifogging coatings based on triethoxysilyl-terminated poly(N-vinylpyrrolidone)

Superhydrophilic multifunctional antifogging coatings based on triethoxysilyl-terminated poly(N-vinylpyrrolidone)

A Facile Strategy to Construct Anti-Swelling, Antibacterial, and Antifogging Coatings for Protection of Medical Goggles.

During the COVID-19 (Corona Virus Disease 2019) pandemic, traditional medical goggles are not only easy to attach bacteria and viruses in long-term exposure, but easy to fogged up, which increases the risk of infection and affects productivity. Bacterial adhesion and fog can be significantly inhibited through the hydrogel coatings, owing to super hydrophilic properties. On the one hand, hydrogel coatings are easy to absorb water and swell in wet environment, resulting in reduced mechanical properties, even peeling off. On the other hand, the hydrogel coatings don't have intrinsic antibacterial properties, which still poses a potential risk of bacterial transmission. Herein, an anti-swelling and antibacterial hydrogel coating is synthesized by 2-hydroxyethyl methacrylate (HEMA), acrylamide (AM), dimethylaminoethyl acrylate bromoethane (IL-Br), and poly(sodium-p-styrenesulfonate) (PSS). Due to the self-driven entropy reduction effect of polycation and polyanion, an ion cross-linking network is formed, which endows the hydrogel coating with excellent antiswelling performance. Moreover, because of the synergistic effect of highly hydrated surfaces and the active bactericidal effect from quaternary ammonium cations, the hydrogel coating exhibits outstanding antifouling performances. This work develops a facile strategy to fabricate anti-swelling, antifouling, and antifogging hydrogel coatings for the protection of medical goggles, and also for biomedical and marine antifouling fields.

Biocompatibility of antifogging SiO-doped Diamond-Like carbon laparoscope coatings

Laparoscopes can suffer from fogging and contamination difficulties, resulting in a reduced field of view during surgery. A series of diamond-like carbon films, doped with SiO, were produced by pulsed laser deposition for evaluation as biocompatible, antifogging coatings. DLC films doped with SiO demonstrated hydrophilic properties with water contact angles under 40°. Samples subjected to plasma cleaning had improved contact angle results, with values under 5°. Doping the DLC films with SiO led to an average 40% decrease in modulus and 60% decrease in hardness. Hardness of the doped films, 12.0 – 13.2 GPa, was greater than that of the uncoated fused silica substrate, 9.2 GPa. The biocompatibility was assessed through CellTiter-Glo assays, with the films demonstrating statistically similar levels of cell viability when compared to the control media. The absence of ATP released by blood platelets in contact with the DLC coatings suggests in vivo hemocompatibility. The SiO doped films displayed improved transparency levels in comparison to undoped films, achieving up to an average of 80% transmission over the visible spectrum and an attenuation coefficient of 1.1 × 104 cm−1 at the 450 nm wavelength. The SiO doped DLC films show promise as a method of fog prevention for laparoscopes.

Robust antifogging coatings with ultra-fast self-healing performances through host-guest strategy

Given the vulnerability of conventional antifogging coatings to mechanical damage, self-healing capability can significantly restore their functionality, but are difficult to materialize quickly and effectively. Herein, we report a facile UV-curable antifogging coating, based on host–guest interaction to obtain both ultra-fast self-healing performance and robust mechanical properties. Initially, a pair of host–guest supermolecules (HGSM) consisting of acrylic β-cyclodextrin (Aβ-CD) and acrylic adamantane (AAM) are synthesized and utilized as cross-linkers. Together with hydrophilic and hydrophobic moieties, 2-acrylamide-2-methylpropane sulfonic acid (AMPS) and methyl methacrylate (MMA), a robust antifogging coating with ultra-fast self-healing ability is developed via a facile UV curing process. Benefitting from the delicate balance of both hydrophilic and hydrophobic constituents, the resultant coatings display excellent antifogging performance with ∼90 % of light transmission, ranging from −20 °C to 85 °C. The unique non-covalent host–guest structure was covalently integrated into a cross-linked network, as-prepared coating and bulk gel exhibited ultra-fast self-healing capability, needing only ∼15 s to completely heal the cracks under the hot-steam environment (85 °C). And the bulk gels with host–guest recognition can significantly improve its self-healing efficiency to ∼88.3 %, significantly greater than its H-bonding counterpart (43.5 %). Notably, the prepared coating with strong adhesion properties (∼431 KPa) is robust enough to withstand 1,000 cycles of abrasion and 2 h of water immersion to maintain excellent antifogging performance. This strategy might open new avenues for accelerating the use of host–guest assembly to rapidly build effective antifogging/self-healing coatings and promote their applications in more harsh fogging conditions.

Tailoring amphiphilic polymeric coating with durable antifogging performance

Foggy surfaces can damage the optical performance of devices and even cause adverse consequences like safety concerns in some cases. Various antifogging coatings have been proposed to relieve this trouble. Nevertheless, most coatings suffer from temporary fog-repellency features due to hygroscopic swelling behavior and detachable interface. Herein, we reported an antifogging coating with persistent fogging prevention via the introduction of the amphiphilic polymer and interfacial layer. With the aid of benzophenone (BP) groups, both bulk crosslinking and interfacial bonding were achieved to prevent relatively macroscopic motions of coating from the substrate under extreme conditions. In virtue of the minor swelling and interfacial adhesion, the coating could preserve the fog-free behavior after 50-cycle antifogging tests and even aging for 90 days under harsh conditions. Notably, both in vitro (pig larynx) and vivo (living rabbit) outcomes indicated excellent fog-repellency of the polymer-coated endoscope.

Robust superhydrophilic antifogging coatings by a facile sol–gel method

Robust superhydrophilic antifogging coatings by a facile sol–gel method

Investigation of an oleophobic-hydrophilic polymer brush with switchable wettability for easy-to-clean coatings

The combination of different wetting states, such as hydrophilic and oleophobic, in an adaptive polymer layer provides new opportunities in the field of easy-to-clean and anti-fog coatings. In this work, the synthesis of new end-functionalized well-defined block copolymers consisting of a hydrophilic poly(acrylic acid) (PAA) block and an oleophobic poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate) (PHFIPMA) block of different block length was investigated. This was achieved by parallel synthesis of the single blocks separately using atom transfer radical polymerization (ATRP), and subsequent block coupling by copper(I)-catalyzed click chemistry. A hydroxy end-group functionalization allowed these polymers to be assembled into dense polymer brushes via a grafting-to approach. The architecture of theses brushes and the orientation of the chains within the films were studied using angle-resolved X-ray photoelectron spectroscopy (ARXPS). To study the influence of the lengths and ratio of the two blocks on the switching of the wettability, contact angle measurements were performed demonstrating the correlation between structure and functionality. It was found that an increasing length of the hydrophilic block, while keeping the length of the oleophobic block constant, leads to an increase of the switching amplitude. Molecular Dynamic Simulations, which gave deeper insights into changes of the brush architecture during switching, enabled in combination with chemical analysis at the nanometer scale (ARXPS) conclusions about the influence of molecular rearrangements inside the brush on macroscopic changes at the outer surface of the brush due to external stimuli. Finally, oil spray-off experiments demonstrated the potential of these new adaptive polymer brushes as easy-to-clean coatings.

Transparent UV-Cured Polyurethane–Surfactant Coatings with Antifogging Properties

Fogging on optical devices may severely impair vision, resulting in unacceptable adverse consequences. Transparent antifogging coatings play an important role in daily life, because they can effectively enhance transmission of light and meanwhile prevent water condensation considerably. Herein, highly transparent antifogging polyurethane coatings are designed and fabricated via a UV-assisted cross-linking method. Initially, isophorone diisocyanate, poly(ethylene glycol) (PEG), and 2,2′-bis(hydroxymethyl)butyric acid (DMBA) were thermally polymerized to obtain a series of amphiphilic polyurethane prepolymers. Afterward, polyurethane prepolymers were end-capped by various surfactants (OP-x) and pentaerythritol triacrylate (PETA). Upon photoirradiation, the UV-cured polyurethane coatings with the cross-linking structure were obtained. Subsequently, the polyurethane coating has a hierarchical surface due to microphase separation. The wettability of coatings could be mainly attributed to the cooperative effect between the hierarchical surfaces and the hygroscopicity of the surfactant molecules. The polyurethane coating enables water to rapidly spread out, fulfilling the enhanced antifogging function (without forming water droplets). This antifogging material may find potential application in microdevices and engineering systems that operate in a cold or humid environment.