A comprehensive study was conducted to develop structurally robust, crack-suppressed superhydrophilic nanocomposite coatings comprising poly(acrylic acid) (PAA) and silica nanoparticles. We systematically investigated the critical trade-off between particle loading, which drives surface wettability and stress-induced crack formation driven by capillary forces and shrinkage mismatch. Our findings identify a distinct structural failure threshold between 25 and 30 vol.% silica under conventional drying. By strategically optimizing drying kinetics (an initial flash-dry at 120 °C for 1 h followed by a 24 h ambient cure), we successfully fabricated transparent, crack-suppressed superhydrophilic coatings at elevated silica loadings up to 47 vol.%, establishing a practical, scalable framework for advanced functional surface engineering. The crack-suppressed mechanism was hypothesized to be related to internal stress.

This study investigates the influence of PFAS-free superhydrophobic treatment on the performance of NYCO (50% Nylon 50% Cotton) fabric. The primary focus is to assess how these treatments influence key performance attributes, including water repellency, weight gain, air permeability, and color stability. The treatments were formulated using a silica/epoxy diluted with isopropanol (IPA), with the goal of achieving minimal weight gain (<10%) and high water repellency (AATCC22 rating of 80 or above) with a minimal impact on breathability and visual appearance. A series of formulations were prepared with a a constant silica to epoxy ratio (3:7) while varying the solids content of the suspension (1.8 to 5.2 wt.%). Treated fabrics were evaluated through water spray tests (AATCC TM 22), air permeability (ASTM D737), spectrophotometric color analysis, and SEM surface morphology. Samples treated with a formulation containing 2.0 wt.% solids content demonstrated the best performance characteristics: low weight gain, minimal breathability reduction, low color change, and water repellency. The findings reveal the potential for a PFAS-free treatment to achieve high water repellency while maintaining other key fabric performance characteristics. The results contribute to the advancement of sustainable, high-performance protective textiles for military applications.

Abstract Additive manufacturing has revolutionized polymer material engineering, yet it remains heavily reliant on petroleum-based polymers and non-recyclable thermosets, particularly in vat-photopolymerization. This review evaluates the ongoing transition toward sustainable 3D printing and identifies a critical “functionalization paradox”: the chemical modifications required to make bio-derived feedstocks printable often increase their carbon footprint and compromise their inherent biodegradability. Herein, we categorize sustainable materials through a two-pronged circularity roadmap. First, after reviewing bio-based functionalized monomers, we review inherently reactive bio-monomers, such as lipoic acid derivatives, which bypass synthetic modification to enable rapid polymerization and closed-loop chemical depolymerization. Second, we review covalent adaptable networks (CANs) as a potential solution for thermosets that require synthetic functionalization, providing a pathway to reprocessability. Finally, we conclude that achieving truly circular 3D printing requires a fundamental shift in design philosophy: moving from the functionalization of biomass to the exploration of natural molecular architecture and dynamic network topologies.

Adhesives are crucial in industries ranging from aerospace to consumer electronics, yet their reliance on non-recyclable polymers presents significant environmental and economic challenges. Despite progress in dynamic and reversible chemistries, current solutions often compromise either performance or sustainability. This study proposes a solvent-free, radiation-curable adhesive that addresses these limitations by combining rapid curing within 30 seconds under a wide range of visible wavelengths (400–700 nm) and demonstrates constant adhesion strength across diverse substrates. Recycling is achieved using a simple household microwave, obviating the need for solvents or elevated temperatures while maintaining the adhesive’s performance over multiple cycles. Furthermore, the adhesive’s optical transparency and high refractive index enable its use in various optical applications, whereas its robustness in wet conditions expands its potential for bioadaptive or underwater systems. This adhesive represents an innovative and significant step toward sustainable adhesives that seamlessly integrate high performance with circular economy principles.

In this study, particle loading, polyfluorinated alkyl silanes (PFAS or FAS) content, superhydrophobicity, and crack formation for nanocomposite coatings created by the spray coating process were investigated. The formulations comprised hydrophobic silica, epoxy resin, and fluorine-free or FAS constituents. The effect of FAS content and FAS-free compositions on the silica and epoxy coatings’ chemistry, topography, and wetting properties was also studied. All higher particle loadings (~30 wt.%) showed superhydrophobicity, while lower particle loading formulations did not show superhydrophobic behavior until 13% wt. FAS content. The improved water repellency of coatings with increased FAS (low particle loadings) was attributed to a combination of chemistry and topography as described by the Cassie state. X-ray photoelectron spectroscopy (XPS) spectra showed fluorine enrichment on the coating surface, which increases the intrinsic contact angle. However, increasing the wt.% of FAS in the final coating resulted in severe crack formation for higher particle loadings (~30 wt.%). The results show that fluorine-free and crack-free coatings exhibiting superhydrophobicity can be created.

Radiation curing (photocuring) of thermosetting polymers, such as acrylate resins, is a common technology with diverse applications, such as in adhesives, coatings, advanced manufacturing, medical-related technologies, and more. Photocuring of acrylate thermosets is initiated via a radical-induced cleavage of a photocuring agent, like bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (BAPO), which activates the vinyl C=C double bond of the acrylate moiety. Here, we show that addition of semiconducting WS2 nanoparticles (NPs) accelerates the photocuring process. Using electron paramagnetic resonance (EPR) of ethanol-water solutions, the mechanism of the radical reactions of BAPO and WS2 NPs is investigated. It is found that the two photocuring agents operate according to entirely different mechanisms, which has been discussed in great detail. In contrast to BAPO, which is photocleaved during the curing process, the WS2 NPs remain unchanged, leading to major mechanical reinforcements of the cured acrylate film.

Adhesives with polymeric bases are indispensable in joining various surfaces across numerous industries and applications. The recognition of environmental concerns and the demand for sustainable materials has spurred researchers to explore innovative strategies for improving the recyclability of polymeric adhesives. These adhesives are mostly thermosets-based, thus, infusible and insoluble in nature. This review discusses potential solutions for implementing covalent adaptable networks (CANs) in thermoset adhesives to enable their recycling. Insights into the factors influencing these adhesives’ recyclability and practical applications are provided, paving the way for a comprehensive understanding of their potential impact on sustainable adhesive technologies. Whereas thermal-assist CANs dominate the field of recyclable adhesives, several other stimuli, like pH and light, are also discussed, though further research is needed to make them more applicable.

Cationic photo-initiated and polymerized epoxies are characterized by good adhesion, high modulus, zero volatiles, low shrinkage and living polymerization characteristics. Radiation—cured acrylate resins are characterized by rapid initial curing with increased initial strength. The combination of radiation-cured acrylates and epoxies may present advantageous attributes. Thus, the system investigated is a hybrid epoxy/methyl acrylate and three different initiators for cationic polymerization of epoxies, the radical reaction of acrylates and the thermal initiator. When incorporating additives like opaque WS2 nanoparticles (NPs), absorption of the photo radiation takes place, which may lead to low photo activity. Curing kinetics measurements revealed that the absorbing/masking effect of WS2 was insignificant, and surprisingly, the level of curing was enhanced when the WS2 NPs were incorporated. FTIR results demonstrated that covalent bonds were formed between the inorganic fullerenes (IF-WS2) and the crosslinked matrix. Viscosity measurements showed a surprising reduction of five to ten times in the low-shear viscosity upon NPs incorporation compared to neat resins. It was concluded that the decrease of viscosity by the inorganic NPs, in addition to the enhanced level of conversion, has profound advantages for structural adhesives and 3D printing resins. To the best of our knowledge, this investigation is the first to report on a radiation-induced curing system containing opaque WS2 NPs that leads to an enhanced degree of curing and reduced shear viscosity.

The most prevalent materials used in the Additive Manufacturing era are polymers and plastics. Unfortunately, these materials are recognized for their negative environmental impact as they are primarily nonrecyclable, resulting in environmental pollution. In recent years, a new sustainable alternative to these materials has been emerging: Reversible Covalent Bond-Containing Polymers (RCBPs). These materials can be recycled, reprocessed, and reused multiple times without losing their properties. Nonetheless, they have two significant drawbacks when used in 3D printing. First, some require adding new materials every reprinting cycle, and second, others require high temperatures for (re)printing, limiting recyclability, and increasing energy consumption. This study, thus, introduces fully recyclable RCBPs as a sustainable approach for radiation-based printing technologies. This approach enables multiple (re)printing cycles at low temperatures (50 °C lower than the lowest reported) without adding new materials. It involves purposefully synthesized polymers that undergo reversible photopolymerization, composed of a tin-based catalyst. An everyday microwave oven quickly depolymerized these polymers, obtaining complete reversibility.

The radiation curing paradigm of opaque WS2 nanoparticle (NP)-based epoxy/acrylate nanocomposites was studied and found to exhibit both a reduction in viscosity and an enhanced degree of curing when incorporating WS2 NPs. The objective of this study was to investigate the mechanical, thermal, and physical properties of a radiation-induced and cured epoxy/acrylate blend containing 0.3 to 1.0 wt.% WS2 NPs. Experimental results indicate that the tensile toughness increased by 22% upon optimizing the NP content compared to that of WS2-free formulations. Tensile fractured surfaces with different WS2 NP contents were analyzed with a scanning electron microscope and an atomic force microscope and showed distinctive morphology depending on the WS2 NP content, supporting the results of the tensile test. The energy required to break shear adhesion specimens demonstrated an increase of up to 60% compared to that of the neat resin. The glass transition temperature determined by dynamic mechanical analysis presented similar or higher values upon WS2 NP incorporation. Furthermore, up to 80% improvement in impact strength was demonstrated when WS2 NPs were dispersed in the epoxy/acrylate blend. It was concluded that the surface chemistry and dispersion level of the WS2 NPs are the major variables affecting the macro properties of cationically radiation-cured resins and their adhesion properties. This study is the first to demonstrate the possibility for radiation-induced curing of opaque NPs based on WS2 that serve as both a reinforcement nanoparticle at low concentrations and an enhancement of the degree of curing.

Superhydrophilic coatings based on a hydrophilic silica nanoparticle suspension and Poly (acrylic acid) (PAA) were prepared by dip coating. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to examine the morphology of the coating. The effect of surface morphology on the dynamic wetting behavior of the superhydrophilic coatings was studied by changing the silica suspension concentration from 0.5% wt. to 3.2% wt. while keeping the silica concentration in the dry coating constant. The droplet base diameter and dynamic contact angle with respect to time were measured using a high-speed camera. A power law was found to describe the relationship between the droplet diameter and time. A significantly low experimental power law index was obtained for all the coatings. Both roughness and volume loss during spreading were suggested to be responsible for the low index values. The water adsorption of the coatings was found to be the reason for the volume loss during spreading. The coatings exhibited good adherence to the substrates and retention of hydrophilic properties under mild abrasion.

[4 + 4] and [2 + 2] cycloadditions are unique reactions since they form and deform cycloadducts under irradiation due to their inherent reversible nature. Whereas promising for the field of recycling, these reactions usually suffer from two major shortcomings: long reaction durations (hours) and the requirement of high-intensity light (∼100 W/cm2), typically at a short wavelength (<330 nm). We demonstrate several tetra-dentate catalysts that can overcome these fundamental limitations. Among them is a tin complex that enables 76% conversion within only 2 min of irradiation at 395 nm, much faster than the known ruthenium-based catalyst, under irradiation with light intensity two orders of magnitude lower than that reported in the literature. Due to the short photopolymerization time, low intensity (27 mW/cm2), and long UV light (395 nm), this unique complex opens new avenues for recycling three-dimensional printing products based on photopolymerization of cycloaddition reactions.

Debond-on-demand adhesives are of growing interest, due to their many advantages – from economic to environmental ones. Several approaches have been demonstrated to obtain this property – from more classic ones (pressure-sensitive adhesives, photodegradable adhesives, biodegradable adhesives, etc.) to more advanced ones (electrically sensitive adhesives, reversible covalent bonds containing adhesives, etc.). With the growing awareness of polymers' environmental impact, several studies have been conducted in the field of Biobased polymers. This trend is also implemented in the field of debondable adhesives by two main approaches – biodegradable adhesives (from polysaccharides like starch, through oils like epoxidized castor oil, to protein derivatives-based adhesives) and Biobased reversible covalent bonds containing polymers (RCBPs)-based adhesives, like those obtained from reacting an epoxidized soybean oil with natural carboxylic acids. The RCBPs debond-ability is far more efficient, as, unlike biodegradable adhesives, these can re-bond after the debonding process is finished.

The effect of semiconducting tungsten disulfide (WS2) nanoparticles (NPs), functionalized by either methacryloxy, glycidyl, vinyl, or amino silanes, has been studied in photocuring of acrylate and epoxy resins (the latter photocured according to a cationic mechanism). The curing time, degree of curing (DC), thermal effects, and mechanical properties of the radiation-cured resins were investigated. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analyses confirmed that a silane coating was formed (1-4 nm) on the NPs' surface having a thickness of 1-4 nm. Fourier transition infrared (FTIR) was used to determine the DC of the nanocomposite resin. The curing time of the epoxy resin, at 345-385 nm wavelength, was 10 to 20 s, while for acrylate, the curing time was 7.5 min, reaching 92% DC in epoxy and 84% in acrylate. The glass transition temperature (Tg) of the photocured acrylates in the presence of WS2 NPs increased. In contrast to the acrylate, the epoxy displayed no significant variations of the Tg. It was found that the silane surface treatments enhanced the DC. Significant increases in impact resistance and enhancement in shear adhesion strength were observed when the NPs were treated with vinyl silane. A previous study has shown that the addition of WS2 NPs at a concentration of 0.5 wt.% is the optimal loading for improving the resin's mechanical properties. This study supports these earlier findings not only for the unmodified NPs but also for those functionalized with silane moieties. This study opens new vistas for the photocuring of resins and polymers in general when incorporating WS2 NPs.

A review of dual-cured hydrogel systems for bioadhesives and various biomedical applications was conducted. Most studies in the review cover those systems published in the last decade. Utilizing a dual-curing process for the fabrication of hydrogels can achieve desired chemical structures and provide the ability to create high-performance hydrogel materials with remarkable control over the material's final properties. Implementing dual-curing in the hydrogels fabrication process can be achieved easily using standard lab equipment without making the processing stage very complex and can be performed in short periods. Moreover, the dual-curing process can help overcome some of the significant drawbacks of using hydrogel materials, including low mechanical properties making the intermediate and final product difficult to handle before the end-use. This combination of the dual-curing process and the fabrication of hydrogels can improve the utilization of hydrogels as bioadhesives and make them more suitable for the desired adhesion. Also dual-cured hydrogels can greatly contribute to their usage in other biomedical applications, such as in tissue engineering, wound dressing and drug delivery making these a desirable area of study.

Surface modification of tungsten disulfide (WS2) nanoparticles (NPs) by a photo-initiator (PI) for radical curing of acrylate nano-structured systems has been studied with the purpose of acquiring covalent bonding of the acrylate matrix to the NPs surface. This surface functionalization was expected to photosensitize both the PI and the NPs thereby enhance the photocuring of the acrylate as well as improving its mechanical properties. The studied PI was the commonly used Bis(acyl) phosphane oxides (BAPOs). For surface modification of the WS2 NPs, the BAPO was functionalized first with Tri(methoxy) silane (TMESI) to yield TMESI-BAPO moieties. Subsequently, the functionalized BAPO was chemisorbed to the WS2 NPs resulting in WS2 NPs surface modified by TMESI-BAPO pendant moieties. The functionalization and surface modification were confirmed using spectroscopic techniques as well as electron microscopy, and thermal measurements. Thermal gravimetric analysis (TGA) displayed 40 wt% weight loss for TMESI-BAPO modified WS2 upon heating to 400 °C. The modified WS2 NPs were incorporated into acrylate resin to study the curing kinetics and resulting mechanical properties compared to neat WS2. Nanostructured acrylate with TEMSI-BAPO modified WS2 NPs exhibited an increase of 83% in storage modulus and toughness compared to neat acrylate.

The increasing demand for advanced adhesion performance in thermoset systems, resin-composites, coatings, and complex geometric shapes used in a wide variety of applications has been a driving force for the development of novel dual-cured adhesion techniques. This chapter assesses various types of dual-cured systems that have been introduced in recent years which are based on two different cross-linking mechanisms or two-stage reactive network polymers. The evaluation of the dual-cured systems is conducted by means of chemical mechanisms, types of materials used, curing conditions, and the resulting properties. Furthermore, a list of the commercially available materials used for dual-curing applications is presented accompanied by the description of their properties and functions.

Reversible covalent bonds containing polymers (RCBPs) are novel types of polymers which have the processability of thermoplastics along with the high performances like those of thermosets and thermoplastics. These polymers are usually divided into two main groups—general and dynamic RCBPs. While general ones can fully dissociate under certain conditions, dynamic ones only undergo transformation which under high temperature, allows them to flow. This chapter reviews the polymerization reactions related to RCBPs and RCBPs' rheology, kinetics, processing methods, mechanical properties, and potential applications. In the reviewed polymerization kinetics, three main methods have been used—Fourier transform infrared, H1-nuclear magnetic resonance, dynamic mechanical analysis, and parallel plates rheometer. With respect to processing, it was realized that conventional processing methods, such as extrusion and injection molding, could be used. While dynamic RCBPs mostly exhibit low mechanical properties, some general RCBPs display enhanced properties, comparable to high-performance thermoplastics and some thermosets. According to literature, the RCBPs with the highest mechanical properties are the Schiff-base containing materials. As RCBPs are novel polymers, only a few applications have been identified, most of them in the field of composite materials, biomedical industries, membranes, and batteries.

Since ice formation on surfaces at subzero temperatures leads to accidents, increased equipment maintenance costs, and reduced performance, multiple strategies, including superhydrophobic surfaces and coatings, have been explored as means to reduce ice adhesion to solid surfaces. Previous work has correlated the effect of topography of regularly patterned superhydrophobic surfaces with ice adhesion. This work, however, investigated the effect of filtered topography on ice adhesion for random superhydrophobic surfaces. The ice adhesion behavior of superhydrophobic composite coatings, prepared from a mixture of silica nanoparticles and polymer binder and sprayed on glass slides, was determined using a shear strength measurement. The ice adhesion significantly decreased with an increase in particle content up to 40 wt.

The adverse environmental effects (UV radiation and oxidation) on polyethylene films' durability significantly shorten their service life. This work was aimed to study the influence of incorporation of nanoparticles (hydrophobic nanosilica and Na+ nanoclays) to UV stabilized films (by hindered amine light stabilizer - HALS) on sustaining their properties by delaying the loss of the HALS from linear low-density polyethylene (LLDPE) films under photo-oxidative and humid environments. Results demonstrated that the incorporation of nanoclays to the stabilized film increased the photo-oxidative degradation of the LLDPE due to enhanced loss of the HALS from the nanocomposite film. In contrast, the addition of nanosilica delayed the loss of HALS under the same harsh conditions. The slower loss of HALS was attributed to the introduction of a longer diffusion path for the HALS molecules provided by the well-dispersed hydrophobic nanosilica particles and the immobilization effect resulting from the chemical affinity between the hydrophobic nanosilica and the hydrophobic sites on the HALS molecules. The HALS's increased retention in the LLDPE/nanosilica nanocomposite film resulted in extended retention of the film's mechanical properties. (C) 2021 Elsevier Ltd. All rights reserved.