Freshwater crisis is a global problem and seeking more sources of fresh water is the key to solving this problem. Solar water purification and fog collection are two separate ways to obtain fresh water. However, neither of these methods could operate 24/7 when used alone. Herein, we report a hydrogel membrane that can achieve both solar water purification and fog collection, thus enabling all-day freshwater collection. The hydrogel membrane with microstructured patterns inspired by the structure on the back of the Namib Desert beetle consists of poly(vinyl alcohol) (PVA), chlorine-reinforced polypyrrole (PPy-Cl), and silicon dioxide nanoparticles (SiO2NPs), which is capable of harvesting up to 25 L of fresh water per square meter per day under the outdoor conditions. The excellent freshwater collection capacity is realized based on the synergetic interaction among the hydrophilicity of PVA, the photothermal conversion capacity of PPy-Cl, and the biomimetic microstructures. Furthermore, due to the improved mechanical properties brought by SiO2NPs, the hydrogel-based evaporator reported in the current study has better water resistance as well as mechanical properties, which allows it to be used outdoors for long periods of time and facilitates its practical application.

Incorporating the active medium in a photonic crystal (PhC) structure enables a unique way to engineer the light–matter interaction, leading to the tunability of nonlinear optical responses. The nonlinear optical response of a nanometer-size nonlinear medium can be significantly enhanced by implementing a dielectric periodic structure that facilitates the confinement of light. Hereby, we demonstrated the band edge-assisted enhancement of optical nonlinearity in a one-dimensional polymeric PhC structure consisting of graphene quantum dots (GQD) as the active material. GQDs were synthesized through pulsed laser irradiation of toluene, and they were integrated into the alternative layers of polyvinyl carbazole (PVK) of a PVK/cellulose acetate PhCs. The lower-frequency photonic band edge is precisely tuned to match the excitation wavelength used for the nonlinear optical studies. The open-aperture Z-scan studies of the fabricated structure at 532 nm reveal a substantially enhanced nonlinear absorption property and optical limiting action. The enhanced nonlinear activity is attributed to the slow light effect at the photonic band edge, which improves the electron–photon interaction and, consequently, the local field of interacting laser pulses. The optical limiting threshold of the PhC structure incorporated with GQD is found to be ∼0.38 J/cm2, and it is superior to many reported benchmark values. Findings of the study open up avenues to realize nonlinear photonic devices such as optical limiters, on-chip integrated devices, and optical switches in the future.

It is difficult for any marine engineering equipment to avoid the impact of biofouling. Especially, for engineering equipment made of titanium with a high biocompatibility, biofouling is a thorny problem. The outstanding anti-biofouling properties of the slippery liquid-infused porous surfaces (SLIPSs) and the grafted polydimethylsiloxane (gPDMS) brush surfaces have attracted the attention of researchers. However, the durability and stability of the conventional SLIPSs and the wear resistance of gPDMS are insufficient and should be improved. In this work, PDMS molecule brushes were grafted onto a micro-arc oxidized porous surface infused with a lubricant (silicone oil) to develop a grafted SLIPS (gSLIPS) on a titanium alloy (TA2). The gPDMS molecule brushes have a stronger chemical affinity with silicone oil, which can preserve more lubricants to enhance the durability and stability of the SLIPS. Simultaneously, the infused lubricant in the micro-arc oxidized porous surface can improve the wear resistance of the grafted molecule brushes. Besides, the molecule brushes can further isolate the vulnerable titanium substrate from the biofouling microorganisms. By combining the advantages of the SLIPS and gPDMS, the gSLIPS has excellent stability, durability, and mechanical robustness. The gSLIPS possesses a better biofouling resistance than TA2 and gPDMS. For example, the coverage of Chlorella on the gSLIPS is 0.067% ± 0.022% after being immersed for 14 days, which reduces by 98.8 and 95.6% compared with those on TA2 and gPDMS, respectively. In addition, the gSLIPS also has excellent anti-protein property. Therefore, this method will help develop a more stable, durable, and mechanically robust super-slippery coating with excellent anti-biofouling performance, which has great potential for the extensive titanium applications in marine engineering.

In this work, hydrophobic association physical hydrogels were prepared by photoinitiated copolymerization of acrylic acid and butyl acrylate, followed by water immersion. The chemical structure, mechanical properties, self-healing behavior, and self-recovery properties of the physical hydrogels were studied in detail. The hydrogel possessed a large number of carboxyl groups owing to its high content of acrylic acid, and it was used to adsorb cationic dye. Different from brittle chemical hydrogels, the as-prepared physical hydrogels exhibited good tolerance to microwave heating. Thus, the dye-adsorbed hydrogel was successfully applied for microwave-assisted Fenton degradation of cationic dyes. Starting from the unique structure and properties of physical hydrogels, this work successfully explored application scenarios of these systems in dye adsorption and microwave-assisted degradation. The present findings will contribute to understand the relationships among structure, properties, and practical applications of physical hydrogels.

Utilization of biomass-derived monomeric building blocks to formulate polyurethane materials can significantly reduce the complexity of the target network generated by the uncertainty of raw biomass. Herein, in this study, four cleavable vanillin-based polyols were prepared from vanillin and two sustainable feedstocks, 2,5-furandicarboxylic acid (FDCA) and terephthalic acid (TPA), followed by the cross-linking with two different isocyanates. The resulting polyurethane samples exhibited reasonable mechanical strength, thermostability, and solvent resistance. Of great importance is that the inherent ester bonds in the network endowed these samples with outstanding degradability, evidenced by the impressive weight loss in aqueous NaOH solution at room temperature (weight loss of up to ∼35% after 24 h). Notably, the glass-transition temperature (Tg) of these materials can be tunable by using different isocyanates, ranging from 26 to 101 °C in this work, which could potentially meet application requirements in different fields. This study provides an encouraging first step in formulating mechanically strong, thermally stable, and easily degradable polyurethane samples that are potentially useful in practical applications (i.e., coating and packaging).

The soft actuators capable of responding to multiple stimuli and adapting to changing environments have attracted growing interest in the flexible multifunctional materials. However, how to achieve high degree of freedom (DoF), precise control, and complex shape transformation of the multi-stimuli responsive soft actuator, still remains challenging. Here, we report a multi-responsive soft actuator with various controllable sophisticated deformations by integrating a magnetically sensitive elastomer (MSE) with a liquid crystal elastomer (LCE). Through regulating the stimuli strength and the geometrical dimensions and material parameters of elastomers, the bending angle and curling curvature of the actuator are accurately controlled ranging from 0 to 58.9° and from 0.23 to 1.29 cm–1, respectively. The facile material-structural synergistic design drives the complex 3D shape deformations (e.g., bidirectional bending, shrinkage/bending, rolling/bending, and twisting/bending) of the actuator. More importantly, due to its photosensitive characteristics, the shape-morphing of the actuator can be manipulated locally and sequentially, which markedly enriches the DoFs. The flower-shaped actuator displays multiple deformation modes, and the hand-shaped actuator transforms between 8 gestures under the control of laser and magnetic field, proving that the multi-responsive soft actuators have great application potentials in future bioengineering, soft manipulators, and flexible electronics.

The concurrent utilization of chemotherapy and photodynamic therapy (PDT) can successfully slow the growth of tumors while minimizing systemic toxicity. An injectable temperature-sensitive hydrogel was constructed based on Pluronic F127 and phycocyanin (PC). Nanoparticles formed by self-assembly of doxorubicin and ursolic acid (DOX–UA NPS) were further loaded into the hydrogel to give a local drug delivery platform (DOX–UA NPs@Gel). DOX–UA NPs@Gel can be enriched in situ in tumors and continuously release DOX–UA NPs and free PC. UA can promote the responsiveness of tumor cells to DOX. As a natural photosensitizer, PC can produce reactive oxygen species (ROS) when exposed to laser radiation and has significant PDT activity. The MTT assay demonstrated that DOX–UA NPs@Gel under irradiation caused the highest cytotoxicity at 91.6%. The anti-tumor efficiency of various nanoparticles and nanoparticle-loaded hydrogels (the injection dose of DOX is 6 mg/kg) was verified in the H22 tumor-bearing mice (male ICR). In vivo antitumor results demonstrated that DOX–UA NPs@Gel with the combination of chemotherapy and PDT exhibited unique anticancer efficacy with low toxicity. When exposed to radiation after the experiment, the DOX–UA NPs@Gel showed a tumor volume of merely 319 mm3, displaying an exceptional tumor growth inhibition rate of 91.05%. Therefore, the local drug delivery system based on the thermosensitive hydrogel can effectively achieve synergistic antitumor effects.

Herein, we present a method to control the dual cross-linking of radical and urethane reactions for the enhanced polymer coatings by protecting and deprotecting vinyl functionalities using sulfoxide chemistry. We exploited this chemistry to produce highly cross-linked polymers suitable for use as protective coatings. Briefly, dually cross-linkable polymers with sulfoxide-protected vinyl and hydroxyl functionalities were synthesized. Subsequently, thermal curing resulted in the reaction of the hydroxyl functionalities with isocyanate cross-linkers to form urethane cross-links. At the same time, the sulfoxide-protected vinyl functionalities were deprotected and participated in vinyl cross-linking via radical addition reactions. The real-time monitoring of the dual-cross-linking behavior and mechanical properties of the cross-linked films revealed enhanced cross-linking when the reaction rate of the vinyl functionalities was retarded during thermal curing. Thus, this work provides insights into methods of enhancing dual-cross-linking reaction efficiency, and the developed system has applications for the low-temperature preparation of automotive clearcoats.

The integration of catalysts and photosensitizers into a soft matter matrix is an important step for technological deployment and potential repair strategies. Here we present a polyelectrolyte hydrogel platform as a flexible and reusable heterogeneous catalyst for hydrogen evolution reaction (HER), combining polydehydroalanine (PDha) hydrogels with Pt nanoparticles (PtNPs). We demonstrate that the PDha hydrogel can readily adsorb the precursor salt at pH 7, allowing for an in situ capping agent-free synthesis of PtNPs upon UV irradiation. When combined with [Ru(bpy)3]2+ via electrostatic attachment and irradiated under visible light, PtNPs@PDha hybrid hydrogels with 6000 ppm of Pt could evolve 6 μmol H2 after 32 h, which leads to a TON of 60 based on the Pt weight fraction, by adding triethylamine as a sacrificial e– donor in 1:1 MeOH/H2O. If the amount of Pt is reduced to 60 ppm, the obtained TON increased to 350, although the evolved H2 amount was reduced to 0.35 μmol. The water uptake of the hydrogel significantly decreased after the attachment of PtNPs and Ru dye. After photocatalytic HER, the characteristic bands of [Ru(bpy)3]2+ (MC at 352 nm and MLCT at 454 nm) in the absorption spectrum of [Ru]@PtNPs@PDha hybrid hydrogels were shifted, presumably due to the degradation of dyes leading to a broad absorption band stretching toward 600 nm with a shoulder visible at 507 nm. Those degraded dyes were investigated by UV–Vis spectroscopy and could be released at low pH values due to the polyampholytic nature of the surrounding PDha hydrogel. Besides the high activity toward HER, the flexible nature of the herein presented hybrid hydrogels renders these materials interesting and promising systems for heterogeneous light-driven catalysis.

Development of materials based on Eucommia ulmoides gum (EUG) has been receiving increasing interest because of its unique properties and abundant natural sources. In this study, EUG monolithic materials with tunable and interconnected pore structures were prepared via modified Pickering high internal phase emulsion. The effects of dispersed phase volume fractions, cross-linkers, and stabilizers on structures and properties of EUG monoliths were systematically investigated. The usage of a surfactant (span 80) was suppressed by the introduction of particles including graphene, cellulose nanocrystals (CNCs), and carbon nanotubes (CNTs). Moreover, the pyrolyzed sample derived from the CNT-stabilized EUG monolith exhibited excellent electromagnetic shield performance. This study demonstrates a method to prepare porous monolithic EUG materials, which may have potential applications for thermal insulation and electromagnetic shielding materials.

Studies have suggested that ecofriendly, inexpensive, and renewable material sources are essential for developing scalable, high-performance mixed matrix membranes (MMMs). With the fact that the second-most prevalent biomacromolecule in the world of plant biology is lignin, this article delineates the effective fabrication of a lignin-based MMM utilizing polysulfone (PSf) as the base material. The influence of PSf and the lignin concentration on the properties of the fabricated membranes was examined. Also, the developed membranes were assessed for surface morphology, roughness, thickness, thermal stability, functional groups, elemental composition, mechanical strength, and hydrophilicity. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies showed that the PSf/lignin membranes possessed a rough and inconsistent morphology and comparatively greater surface porosity. The water contact angle was reduced for the 1.0 wt % PSF/lignin membrane. Furthermore, lignin nanoparticles significantly impacted the membrane surface characteristics and decreased the ζ potential. Under the ideal experimental scenario, M2 (0.5 wt % lignin/PSf) and M3 (1.0 wt % lignin/PSf) membranes demonstrated good pure water flux values and a higher removal of 98.5 and 98.75% of Cr(VI), respectively. EDX analysis of the membranes after filtration affirmed the effective Cr(VI) removal from water. Owing to its low cost, green credentials, simplicity in synthesis, and remarkable efficiency, the newly developed PSf/lignin membrane is best suited for removing Cr(VI) and various other related contaminants from discharge aqueous effluents.

Thermally conductive adhesives have attracted considerable attention in recent years due to their dual functions in promoting interfacial bonding and thermal transfer. A great number of strategies have been explored for producing them. However, most of them are based on irreversible covalent cross-linking resins, which are difficult to be recycled. Herein, we demonstrate a strategy for in situ producing high-performance, recyclable thermal adhesives from common stocks with a reversibly cross-linkable hyperbranched-star copolymer, HBPE@PSF. The copolymer possesses a hyperbranched polyethylene core covalently bearing multiple polystyrene side chains with small amount of furan moieties, which can be synthesized from commercially available ethylene and styrene as the main monomers. As a stabilizer, the copolymer can effectively promote the exfoliation of hexagonal boron nitride (h-BN) in chloroform under sonication to render high-quality boron nanosheets (BNNSs). Moreover, some of the copolymer can be irreversibly adsorbed on the BNNS surface based on the noncovalent CH−π and π–π interactions. From the resultant nanofiller, BNNS/HBPE@PSF composite adhesives have been successfully prepared through an in situ solution cast process directly with the copolymer as the matrix. After the cross-linking via the Diels–Alder reaction, the resultant adhesives simultaneously exhibit excellent interfacial bonding, thermal transfer, and recyclability, despite their extremely low furan content, 0.30 mol %. This has been confirmed to originate from the unique chain structure of the copolymer, which can form a hyperbranched-star, reversibly cross-linking structure in the composite system. The composite adhesives obtained herein may find their important applications as thermal interface materials in the areas of various electronic products.

Magnetically active soft materials (MASMs) demonstrate considerable potential for applications in sensors, biomedicines, and bionic and soft robotics. However, owing to the low viscosity of unmodified MASMs with weak molding stacking ability, these materials cannot be printed directly, making the fabrication of MASMs with complex structures. A modified MASM printing ink and its preparation method are proposed for the problem of material and printing process of MASM 3D, and the effects of fumed silica nanoparticles as the modifier on the rheological and mechanical properties of MASM ink were experimentally analyzed. A direct ink writing (DIW) three-dimensional (3D) printing process using MASM printing inks was also proposed. To obtain a highly accurate and stable printing process, the influence of process parameters such as printing speed, nozzle diameter, printing air pressure, and ink viscosity on the ink line width was analyzed. The experimental results show that the MASM objects with different characteristics and structures can be printed stably and with high accuracy, reflecting the feasibility of the proposed MASM ink and DIW 3D printing process. To further validate the characteristics of the DIW 3D-printed MASM objects, a MASM gripper was fabricated using the prepared MASM ink with DIW 3D printing. The magnetization-programmed MASM gripper exhibited excellent magnetic response and excellent gripping and shape-adaptation capabilities. The gripping force was ∼294 mN. Under the driving magnetic field of 270 mT, the gripping force can be more than 1765% of the weight of the gripper (1.7 g). The results of this study show that the proposed MASM printing ink with the DIW 3D printing process can be used for various applications with high performance.

The cationic ring-opening polymerization of epichlorohydrin co-initiated by BF3•Et2O has been investigated here. Fast synthesis of pure poly(epichlorohydrin) diols (Fn(OH) ≈ 2.0) with controlled molar mass (Mn up to 4000 g mol–1) and low dispersity (Đ < 1.25) was performed both in toluene and in bulk. An original approach was developed here, consisting of first generating in situ the initiator through the BF3•Et2O-catalyzed reaction of ECH with water, leading to a mixture of oligomers with better solubility in the reaction medium than conventional initiators previously used. Then, through a second monomer starved-feed step, polymerization proceeds exclusively through the activated monomer mechanism, allowing perfect control of the polymer growth. The developed procedure was successfully upscaled to 100 g of polymer to validate a future industrial production of PECH, as well as its derivative glycidyl azide polymer (GAP), the most important energetic binder for solid propellants. Additionally, a separate study was performed to elucidate the reasons for coloration of the polymer observed in the course of polymerization and/or under storage.

Self-healing materials are those that can recover from physical or chemical damage autonomously. To be applied in underwater applications such as water treatment, self-healing materials need to demonstrate sufficient healing ability in complex water matrices. Herein, we investigated how monovalent (NaCl) and divalent (MgSO4) ions at concentrations relevant to brackish and seawater salinity impact the self-healing efficiency of a model 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and N,N′-methylenebis(acrylamide) (MBA) hydrogel. It has been assumed that divalent ions would form ionic bonds and act as crosslinkers between viable functional groups (negatively charged oxygens, etc.). However, our results suggest that this assumption needs to be reconsidered. Under concentrations relevant to seawater (35 g/L), magnesium ions hindered self-healing efficiency by ∼30% as measured by recovery of ultimate tensile (UT) strength. On the other hand, they improved self-healing efficiency by ∼100% as measured by recovery of UT strain. A similar trend was also observed for sodium ions. The chemical crosslinker ratio when doubled did not impact self-healing efficiency. These results challenge the assumption that divalent ions always form ionic bonds that enhance healing and that chemical crosslinking alters the self-healing performance.

Chemical derivatives of polyethylenimine (PEI) receptors with either triphenylamine (TPA) or 7-hydroxy-4-methyl-coumarin (Cou) form stable complexes with adenine and guanine nucleotides in water. The host–guest complex modulation is found to be based on noncovalent molecular interactions such as π–π stacking and hydrogen bonding, which are dependent on the aromatic moieties attached to the polyaminic (PEI) backbone. PEI-TPA acts as a chemosensor with a recognition driving force based on aggregation-induced emission (AIE), involving π–π interaction between the nucleic base and TPA. It detects GTP by a chelation enhancement quenching effect of fluorescence (CHEQ) with a measured logarithm stability constant, log β = 7.7. By varying the chemical characteristics of the fluorophore, as in the PEI-Cou system, the driving force for recognition changes from a π–π interaction to an electrostatic interaction. The coumarin derivative detects ATP with a log β value one order of magnitude higher than that for GTP, allowing for the selective recognition of the two nucleotides in a 100% aqueous solution. Furthermore, fluorescence lifetime imaging microscopy (FLIM) allows for a correlation between the selectivity of PEI-TPA toward nucleotides and the morphology of the structures formed upon ATP and GTP recognition. This study offers valuable insights into the design of receptors for the selective recognition of nucleotides in water.

We report here the production of higher-order oligomers from the glycolysis of poly(ethylene terephthalate) (PET) by using microwave irradiation in a controlled fashion, instead of its fully glycolyzed product, bis(2-hydroxyethyl)terephthalate (BHET). We show that different catalysts can generate either BHET as the ultimate glycolysis product or higher oligomers of PET under microwave irradiation. Depolymerization of waste PET with an average degree of polymerization (DP) of 417 from water bottles was performed in the presence of 0.25 wt % antimony(III) oxide (Sb2O3) as the catalyst at 240 °C and 400 W microwave power, resulting in an oligomer yield of 96.7% with an average DP of 37. Under these conditions, the conversion of PET to oligomers reached 100% in only 5 min at 240 °C (with a 10 min ramping time) and with a ethylene glycol to PET weight ratio of 2.5. In comparison, under the same reaction conditions, 0.04 wt % of zinc acetate (Zn(OAc)2), a well-known catalyst for PET glycolysis, produces only the BHET monomer in 96.3% yield. Our results demonstrated that by using Sb2O3, the same catalyst that is used extensively for PET synthesis from BHET, under microwave irradiation, the PET glycolysis can be controlled to produce higher PET oligomers as an alternative for a complete chemical depolymerization to the BHET monomer. These oligomers are more suitable for being used as additives for many applications and to produce high-quality second-generation products, including regenerated PET.

The toxicity of fluorosilane and the short lifespan of superhydrophobic surfaces have highly restricted the commercial application of superhydrophobic surfaces for antifouling and anti-icing. In this study, a robust and fluorine-free superhydrophobic textile was prepared using a facile spray-dry method. First, the hydrophobic coating was constructed via powerful covalent bonding between epoxy resin and polydimethylsiloxane (PDMS) using a cross-linker, 3-aminopropyltriethoxysilane (APTES), which provided amplified adhesion to the substrate. Later, micropapillary and lotus-like structures were fabricated through the deposition of nanosilica, which significantly enhanced the “air pillow” effect of the superhydrophobicity. The obtained superhydrophobic surface exhibited a water contact angle up to 162°, which remained >150° after 1200 abrasive cycles. The nanoscale structure was found to be somewhat protected by large-scale micron features, e.g., fabrics, which hindered the formation of hydrophilic defects due to wear. Furthermore, the droplets remained beaded on the surface after enduring extreme physical and chemical conditions. Interestingly, the icing delay time on the fabricated coatings increased by ∼20 times. We believe that the robust nature and easy implementation of this hydrophobic coating along with its excellent anti-icing performance will make superhydrophobic and anti-icing clothing feasible for use in various practical scenarios.

Traumatic brain injury (TBI) is a common clinical disease, and the current hyperbaric oxygen and hypothermia therapy are suboptimal. Traumatic brain injuries were accompanied by acute inflammatory reactions, brain edema, neuron damage, and the destruction of blood–brain barrier. Herein, curcumin-loaded lysine/poly(ethylene glycol) diacrylate (PEGDA) hydrogels were constructed via Michael addition for traumatic brain injury treatments. The curcumin-loaded lysine/PEGDA hydrogels were injected into brain injury defect sites with complex anatomical and irregular structures. The real-time therapeutic effects of the curcumin-loaded hydrogels were evaluated by magnetic resonance imaging (MRI). Curcumin-loaded hydrogels can inhibit the inflammatory reaction and promote nerve repair. The curcumin-loaded hydrogel could provide a promising strategy for traumatic brain injury treatments.

Growing environmental concerns and the goal of a circular economy for polymers necessitate the development of biowaste-based materials and efficient recycling of polymer materials. Here, we developed a series of self-blowing network polyhydroxyurethane (PHU) foams by leveraging the aminolysis and decarboxylation of cashew nutshell liquid (CNSL)-based cyclic carbonate with thiols to release CO2 as a blowing agent; these foams contain up to 80 wt % bio-based content. By systematically varying the blowing agent concentrations, we demonstrated the tunability of the morphologies and mechanical properties of CNSL-based PHU foams. Using dynamic mechanical analysis (DMA), compression testing, and hysteresis testing, we showed that these foams fall into the category of flexible foams with potential as memory foams or resiliency foams. To address the recyclability challenges of thermoset foams, we repurposed these CNSL-based PHU foams into bulk materials and reprocessed them by exploiting the dynamic chemistries of the hydroxyurethane linkages. Notably, the reprocessed bulk networks exhibited full property retention. Moreover, the systematic inclusion of permanent linkages to substitute dynamic cross-links presents an avenue to study the interplay of permanent linkages and cross-link density toward the dynamic characteristics. We showed that average relaxation times and activation energies increase with increasing levels of permanent linkages in the system, demonstrating highly tunable dynamic behaviors in PHU network materials.