Free Radical Polymerization Reaction Research Articles

Two approaches to prepare cationic lignin‐based adsorbents for efficient removal of phosphate ion from wastewater

AbstractIn this work, two types of cationic lignin‐based adsorbents (AL‐METAC and AL‐GTA) were prepared through free radical polymerization or etherification reaction of alkali lignin with 2,3‐epoxypropyl‐3‐trimethylammonium chloride or methylacrylloxyethyl trimethyl ammonium chloride (METAC). The contents of quaternary ammonium groups in the adsorbents were adjusted by changing the dosages of 2,3‐epoxypropyl‐3‐trimethylammonium chloride and METAC to fabricate the adsorbents with excellent adsorption capacity. The structures, aqueous solubility, and physical properties of adsorbents were analyzed. Meanwhile, the effects of adsorbents dosage, pH value of solution, temperature, and ionic strength on the adsorption capacity of adsorbents were also analyzed. These two types of adsorbents exhibited outstanding affinity for phosphate, with a maximum removal efficiency of 51.8 and 73.2 mg/g, respectively. The adsorption processes followed pseudo‐second‐order and Langmuir models well. In addition, the AL‐GTA exhibited higher removal efficiency than AL‐METAC. Moreover, the AL‐METAC and AL‐GTA still retained 69.7% and 69.0% adsorption capacity after four times regeneration. The fabricated lignin‐based adsorbents have potential applications in the removal of phosphate from wastewater, which would promote the high‐value application of lignin.

Directional self-assembly of octavinyl polyhedral oligomeric silsesquioxane on the surface of melamine sponge: Establishing hydrophobic surfaces to improve oil–water separation performance

The continuous increase in industrial organic pollutants has seriously contaminated the natural environment, posing a threat to natural ecosystems and human survival. The preparation of hydrophobic materials with corrosion resistance is crucial for the efficient treatment of emulsified oil–water mixtures in industrial wastewater.Octavinyl polyhedral oligomeric silsesquioxane-coated melamine foam (OV-POSS@MF), possessing hydrophobic properties, was synthesized through a two-step process: initially, a sulfhydryl layer was built up on the surface of the melamine foam, followed by the subsequent assembly of octavinyl POSS onto the melamine foam’s surface via a free radical polymerization reaction between sulfhydryl groups and vinyl moieties. OV-POSS@MF achieves a static water contact angle of 141°, demonstrating its pronounced hydrophobic nature. Moreover, the corrosion resistance, adsorption capacity, oil–water separation efficiency, deformation resistance, and flame retardancy of OV-POSS@MF were thoroughly examined. The results indicate that OV-POSS@MF exhibits strong corrosion resistance and maintains good hydrophobicity even after prolonged exposure to highly acidic and alkaline conditions. Notably, OV-POSS@MF possesses the capability to efficiently and rapidly separate emulsified oil–water mixtures. Furthermore, it retains excellent hydrophobicity even after undergoing up to 100 consecutive compressions or distortions, highlighting its remarkable mechanical resilience. Additionally, OV-POSS@MF demonstrates superior flame retardant properties compared to unmodified melamine foam (MF).

Improved Approach for ab Initio Calculations of Rate Coefficients for Secondary Reactions in Acrylate Free-Radical Polymerization.

Secondary reactions in radical polymerization pose a challenge when creating kinetic models for predicting polymer structures. Despite the high impact of these reactions in the polymer structure, their effects are difficult to isolate and measure to produce kinetic data. To this end, we used solvation-corrected M06-2X/6-311+G(d,p) ab initio calculations to predict a complete and consistent data set of intrinsic rate coefficients of the secondary reactions in acrylate radical polymerization, including backbiting, β-scission, radical migration, macromonomer propagation, mid-chain radical propagation, chain transfer to monomer and chain transfer to polymer. Two new approaches towards computationally predicting rate coefficients for secondary reactions are proposed: (i) explicit accounting for all possible enantiomers for reactions involving optically active centers; (ii) imposing reduced flexibility if the reaction center is in the middle of the polymer chain. The accuracy and reliability of the ab initio predictions were benchmarked against experimental data via kinetic Monte Carlo simulations under three sufficiently different experimental conditions: a high-frequency modulated polymerization process in the transient regime, a low-frequency modulated process in the sliding regime at both low and high temperatures and a degradation process in the absence of free monomers. The complete and consistent ab initio data set compiled in this work predicts a good agreement when benchmarked via kMC simulations against experimental data, which is a technique never used before for computational chemistry. The simulation results show that these two newly proposed approaches are promising for bridging the gap between experimental and computational chemistry methods in polymer reaction engineering.

In vitro and in vivo assessment of gallic acid-chitosan/polycaprolactone conjugate electrospun nanofibers for wound healing

The development of innovative multifunctional wound healing materials based on natural bioactives has attracted a great deal of attention in recent years due to their ability to potentiate the healing process and minimize the challenges linked with conventional wound dressings. The current study demonstrates the development and evaluation of a novel nanofibrous wound healing mat made of Gallic acid-chitosan conjugate (GAC) incorporated within a polycaprolactone (PCL) matrix using an electrospinning technique. The GAC conjugate was synthesized by green synthesis using a free radical polymerization reaction to improve the chitosan's free radical scavenging properties. FTIR, DSC, XRD, and UV spectral analysis characterized the formation of GAC conjugate. The red shift observed in the UV spectrum suggested alterations in electronic transitions resulting from the creation of covalent bonds between Chitosan (CA) and Gallic acid (GA). The appearance of broader and weaker peaks in DSC and the reduced crystallinity in XRD spectrum, signify structural modifications, thereby providing valuable insights into the interaction and structural changes occurring in the GAC conjugates.The SEM image revealed a porous flake-like structural network of GAC conjugate due to the reduced intermolecular hydrogen bonding between them. The functional layer of the nanofibrous mat was produced by electrospinning GAC conjugate with polycaprolactone (PCL) to provide mechanical integrity to the nanofibrous mat. The electrospun nanofibers were characterized using FTIR, DSC, and SEM and evaluated for cell cytotoxicity, angiogenesis, and in vivo wound healing potential in female Wistar rats. The FTIR spectra confirmed the presence of GAC conjugate in the nanofibers, validating the conjugation process. The results demonstrated the successful incorporation of GAC conjugate within the PCL nanofibrous mat, thereby confirming the improvement in the biological properties of the mats. The nanofibrous mat showed angiogenesis activity in the yolk sac membrane assay confirming the property of nanofibers to facilitate cellular adhesion, migration and promotion of angiogenesis with no cytotoxic effect on the viability of mouse stromal cells. On the sixteenth day of therapy, wounds dressed with GAC/PCL nanofibrous mat exhibited a significant improvement in the percent wound closure (94.43%) as compared to the control group (p < 0.05). These results supported the application of GAC/PCL as a novel biomaterial for wound dressing to accelerate the process of wound healing.

Sustained Release of Voriconazole Using 3D-Crosslinked Hydrogel Rings and Rods for Use in Corneal Drug Delivery.

Corneal disorders and diseases are prevalent in the field of clinical ophthalmology. Fungal keratitis, one of the major factors leading to visual impairment and blindness worldwide, presents significant challenges for traditional topical eye drop treatments. The objective of this study was to create biocompatible 3D-crosslinked hydrogels for drug delivery to the cornea, intending to enhance the bioavailability of ophthalmic drugs. Firstly, a series of flexible and porous hydrogels were synthesized (free-radical polymerization), characterized, and evaluated. The materials were prepared by the free-radical polymerization reaction of 1-vinyl-2-pyrrolidinone (also known as N-vinylpyrrolidone or NVP) and 1,6-hexanediol dimethacrylate (crosslinker) in the presence of polyethylene glycol 1000 (PEG-1000) as the porogen. After the physicochemical characterization of these materials, the chosen hydrogel demonstrated outstanding cytocompatibility in vitro. Subsequently, the selected porous hydrogels could be loaded with voriconazole, an antifungal medication. The procedure was adapted to realize a loading of 175 mg voriconazole per ring, which slightly exceeds the amount of voriconazole that is instilled into the eye via drop therapy (a single eye drop corresponds with approximately 100 mg voriconazole). The voriconazole-loaded rings exhibited a stable zero-order release pattern over the first two hours, which points to a significantly improved bioavailability of the drug. Ex vivo experiments using the established porcine eye model provided confirmation of a 10-fold increase in drug penetration into the cornea (after 2 h of application of the hydrogel ring, 35.8 ± 3.2% of the original dose is retrieved from the cornea, which compares with 3.9 ± 1% of the original dose in the case of eye drop therapy). These innovative hydrogel rods and rings show great potential for improving the bioavailability of ophthalmic drugs, which could potentially lead to reduced hospitalization durations and treatment expenses.

Preparation of acrylic metal salt resin containing capsaicin derivative structure and study of anti-fouling properties

Modifications of acrylic resins with environmentally friendly compounds often solve the problems of marine fouling. In this work, capsaicin derivatives-modified acrylic acid resins were successfully synthesized via free radical polymerization and condensation reactions of monomeric acrylic acid, capsaicin derivatives, metal salts and benzoic acid and structurally characterized by infrared spectroscopy and nuclear magnetism. The physicochemical properties of the synthesized resin coatings were tested with a rotary viscometer, gel permeation chromatography, video optical contact angle measurements and a laser confocal tester. The self-polishing and antifouling properties of the resins were investigated with dynamic simulation experiments, algae inhibitions, bacterial inhibition experiments and real sea antifouling experiments. By comparing with the acrylic resin without capsaicin derivatives, the acrylic resin with added capsaicin derivatives had good antifouling performance, and the optimal content was 2.5 %. In summary, the capsaicin derivative-modified acrylic metal salt resins have good self-polishing properties and antifouling properties.

Nanomotor-based H2S donor with mitochondrial targeting function for treatment of Parkinson's disease

Reduction of endogenous hydrogen sulfide (H2S) is considered to have an important impact on the progress of Parkinson's disease (PD), thus exogenous H2S supplementation is expected to become one of the key means to treat PD. However, at present, it is difficult for H2S donors to effectively penetrate the blood brain barrier (BBB), selectively release H2S in brain, and effectively target the mitochondria of neuron cells. Herein, we report a kind of nanomotor-based H2S donor, which is obtained by free radical polymerization reaction between l-cysteine derivative modified-polyethylene glycol (PEG-Cys) and 2-methacryloyloxyethyl phosphorylcholine (MPC). This kind of H2S donor can not only effectively break through BBB, but also be specifically catalyzed by cystathionine β-synthase (CBS) in neurons of PD site in brain and 3-mercaptopyruvate sulfurtransferase (3-MST) in mitochondria to produce H2S, endowing it with chemotaxis/motion ability. Moreover, the unique chemotaxis effect of nanomotor can realize the purpose of precisely targeting brain and the mitochondria of damaged neuron cytopathic diseases. This kind of nanomotor-based H2S donor is expected to enrich the current types of H2S donors and provide new ideas for the treatment of PD.

Thioxanthonation of 2-naphthalene-thioacetic acid as a visible-light photoinitiator: The investigation of photophysical and photochemical properties

Thioxanthonation of naphthalene thioacetic acid (TXNPSCH2COOH) resulted a visible light photoinitiator with the high molar absorptivity (ε405: 5680 L.mol−1.cm−1) in the visible spectral region and made this compound an attractive photoinitiator for free radical polymerization reactions. Low fluorescence quantum yield (ΦF: 0.06 in 2-MeTHF) and comparatively low triplet energy (186 kJ/mol in 2-MeTHF) was in favorable for efficient intersystem crossing to the triplet state which is necessary for production of initiating radicals. Indeed, photopolymerization of methyl methacrylate along with TXNPSCH2COOH (1 × 10−3 M) and a tertiary amine namely MDEA yielded nearly 25% conversion of monomer to polymer. All spectrophotometric studies including laser flash photolysis which gives triplet lifetime of initiator which is very important information for initiation mechanism of photoinitiators, indeed a long enough triplet lifetime of TXNPSCH2COOH (τT: 1000 ns) allows for efficient reactions with co-initiators to generate radicals.

A multi-functional double cross-linked chitosan hydrogel with tunable mechanical and antibacterial properties for skin wound dressing

Chitosan hydrogels with essential antibacterial properties and biocompatibility have great potential in tissue engineering and regeneration medicine. However, pure chitosan hydrogel could be limited by insufficient mechanical properties. In this work, we designed a multi-functional chitosan hydrogel based on the combination of chitosan methacrylate (CTSMA) and sulfhydrated chitosan (CTSSH), which is cross-linked simultaneously by free-radical polymerization reaction and Thiol-ene reaction. The CTSMA/CTSSH (CMS) hydrogels displayed superior tissue adhesive and mechanical properties when compared to pure CTSMA hydrogel. Additionally, the resulting hydrogels exhibited potent antimicrobial effects against both E. coli and S. aureus. Besides, the CMS hydrogels exhibited good biocompatibility as demonstrated by cytotoxicity and cell proliferation experiments using fibroblasts cells (L929) and adipose-derived stem cells (ADSCs). In vivo experiment, the repairing effect of hydrogels on full-thickness skin defect model in rats was studied. Histological and immunohistochemical staining results showed that CMS hydrogels promoted angiogenesis, dermal repair and epidermal regeneration. Overall, the study highlights the potential of the CMS hydrogels as a promising biomaterial in wound healing applications.

Synthesis and properties of elevated temperature hydrogels for enhanced oil recovery based on AM/AMPA/NVP copolymer and silica nanoparticles

AbstractTo improve the stability of polymer gel profile control agents used in high‐temperature and high‐salinity reservoirs, the temperature‐resistant and salinity‐resistant polymer (TSP) was synthesized from acrylamide (AM), 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS), N‐vinyl‐2‐pyrrolidone (NVP) via free radical polymerization reaction using initiator. The TSP showed excellent salt resistance and thermal stability because of the introduction of the sulfonic acid group, hydrophobic group, and rigid group. Furthermore, a novel elevated temperature hydrogel (ETG) for profile control was prepared using TSP, a crosslinker hexamethylenetetramine‐hydroquinone (HMTA‐HQE), and silica nanoparticles as an enhancer. The formula of ETG was as follows: 0.5 wt% TSP + 0.3 wt% HMTA‐HQE + 0.2 wt% silica nanoparticles (enhancer). SEM and FTIR analyzed the micromorphology and composition of ETG. Under high temperature and salinity (110°C, 85702 mg/L), the apparent viscosity of ETG reached up to 3 × 104 mPa·s, and controllable gelation time was 10–20 h. After aging for 120 days at 110°C, the viscosity retention rate was more than 75%, indicating ETG had better thermal stability. Moreover, the plugging ratio of ETG reached up to 97.8%, while the plugging ratio of the conventional HPAM hydrogel was only 81.2%, which indicated that ETG also had good plugging performance.

Curing reactions of liquid hydridopolycarbosilanes with vinyl or allyl groups

AbstractLiquid hydridopolycarbosilanes (LHPCS) with vinyl or allyl groups have attracted significant research interest due to their low curing temperature and high ceramic yield. In this study, allyl‐terminated hydridopolycarbosilane (AHPCS) and vinyl‐terminated hydridopolycarbosilane (VHPCS) were prepared by the Grignard coupling reaction and characterized by NMR and Fourier infrared spectroscopy (FTIR). And the curing reactions of AHPCS and VHPCS with or without initiators (dicumyl peroxide [DCP], tert‐Butyl peroxybenzoate [TBPB]) or Karstedt catalyst were investigated using differential scanning calorimetry and in‐situ FTIR. The main curing reactions of VHPCS and AHPCS are the double bond free radical polymerization and hydrosilylation reaction, respectively. The addition of initiators and Karstedt catalyst could promote the corresponding curing reaction and increase the weight residual at 1000°C. The thermal properties of the cured resins were investigated by thermogravimetric analysis. The addition of initiators and catalyst could significantly increase the weight residual of VHPCS and AHPCS, respectively. The addition of the Karstedt catalyst increased the weight residual of AHPCS from 75.6% to 83.1%. In addition, the addition of TBPB and DCP increased the weight residual of VHPCS from 74.2% to 81.2% and 80.2%, respectively.

Pre-clinical toxicity assessment of Artemisia absinthium extract-loaded polymeric nanoparticles associated with their oral administration.

Background: This study was designed to quantify the composition of the ethanolic extract of Artemisia absinthium through gas chromatography-mass spectrometry analysis and ensure in vivo safety of A. absinthium extract-loaded polymeric nanoparticles (ANPs) before considering their application as a drug carrier via the oral route. Methods: We synthesized N-isopropylacrylamide, N-vinyl pyrrolidone, and acrylic acid crosslinked polymeric NPs by free-radical polymerization reaction and characterized them by Fourier-transform infrared spectroscopy, transmission electron microscopy, and dynamic light scattering spectroscopy. Different concentrations of extract (50mg/kg, 300mg/kg, and 2,000mg/kg body weight) were encapsulated into the hydrophobic core of polymeric micelles for the assessment of acute oral toxicity and their LD50 cut-off value as per the test procedure of OECD guideline 423. Orally administered female Wistar rats were observed for general appearance, behavioral changes, and mortality for the first 30min, 4h, 24h, and then, daily once for 14days. Result: ANPs at the dose of 300mg/kg body weight were used as an initial dose, and rats showed few short-lived signs of toxicity, with few histological alterations in the kidney and intestine. Based on these observations, the next set of rats were treated at a lower dose of 50mg/kg and a higher dose of 2,000mg/kg ANPs. Rats administered with 50mg/kg ANPs remained normal throughout the study with insignificant histological disintegration; however, rats treated at 2,000mg/kg ANPs showed some signs of toxicity followed by mortality among all three rats within 24-36h, affecting the intestine, liver, and kidney. There were no significant differences in hematological and biochemical parameters among rats treated at 50mg/kg and 300mg/kg ANPs. Conclusion: We conclude that the LD50 cut-off value of these ANPs will be 500mg/kg extract loaded in polymeric NPs.

Novel photothermal response intelligent polyurethane sponge with switching wettability for oil/water separation

Intelligent oil–water separation materials with stimulating response have received extensive attention. In this paper, a novel, cost-effective, and simple approach is developed to produce a photothermal-responsive smart sponge with switchable wettability. The polydopamine (PDA) and photothermal agent copper sulfide (CuS) were grafted PU sponge surface. Thermal-responsive polymers P(VTMS-co-NIPAm) and 1-octadecanethiol (ODT) are then decorated on the PDA/CuS@PU surface through free radical polymerization and Michael addition reaction. The obtained PCPO@PU exhibits rapidly switchable wettability between hydrophobicity and hydrophilicity depending on the temperature response of P(VTMS-co-NIPAm) induced by photothermal effect of CuS. The PCPO@PU showed excellent separation performance with oil absorption ratio 8–33 g·g−1 and average self-desorption efficiency of more than 70%, but also has a remarkable recycling effect. Specifically, the photothermal response of PCPO@PU does not require additional chemical initiation and both address the limitations of materials that respond to specific light species and heat. More importantly, the PCPO@PU is able to realize the fluorescent lamp-peristaltic pump model, which can be a significant step toward its widespread application for oil–water separation in nature marine environment.

A Biphasic Hydrogel with Self-Healing Properties and a Continuous Layer Structure for Potential Application in Osteochondral Defect Repair.

The treatment of osteochondral defects remains challenging due to the limited healing capacity of cartilage and the poor results of traditional methods. Inspired by the structure of natural articular cartilage, we have fabricated a biphasic osteochondral hydrogel scaffold using a Schiff base reaction and a free radical polymerization reaction. Carboxymethyl chitosan (CMCS), oxidized sodium alginate (OSA), and polyacrylamide (PAM) formed a hydrogel (COP) as the cartilage layer, while hydroxyapatite (HAp) was incorporated into the COP hydrogel to obtain a hydrogel (COPH) as an subchondral bone layer. At the same time, hydroxyapatite (HAp) was incorporated into the COP hydrogel to obtain a hydrogel (COPH) as an osteochondral sublayer, combining the two to obtain an integrated scaffold for osteochondral tissue engineering. Interlayer interpenetration through the continuity of the hydrogel substrate and good self-healing properties due to the dynamic imine bonding of the hydrogel resulted in enhanced interlayer bond strength. In addition, in vitro experiments have shown that the hydrogel exhibits good biocompatibility. It shows great potential for osteochondral tissue engineering applications.

Polyethylene/poly (N, N-dimethyl acrylamide) hybrid hydrogel membrane for total heat exchanger

For the total heat exchange membrane, there is a compromise effect between the moisture permeability and the gas barrier. To overcome this challenge, a new type of total heat exchange membrane was proposed involving a porous polyethylene (PE) membrane and a hydrophilic poly (N, N-dimethyl acrylamide) (PDMAA) hydrogel. A dense PE/PDMAA composite membrane was fabricated via an in situ photoinitiated free-radical polymerization and cross-linking reaction through a pre-permeation of N, N-dimethyl acrylamide (DMAA) monomers in the porous structure of the PE membrane. In this study, we systematically investigated the effect of varying amounts of PDMAA filler on membrane morphology, hydrophilicity, stability, mechanical properties, water vapor transmission rate, gas barrier property, and total heat exchange efficiency. These results demonstrate that a tight, stable PE/PDMAA hybrid membrane with an interlocked structure has been created. Water vapor diffusion channels and an efficient carbon dioxide (CO2) barrier were successfully constructed through the introduction of a cross-linked PDMAA hydrogel. Improvements in water vapor transmission rate and reduction in CO2 transmission rate were achieved simultaneously with increasing PDMAA filling amount. Excellent mechanical properties and hybrid stability were also observed for the composite membrane obtained. This work provides a novel total heat exchange membrane with convenient production process, low cost and high durability characteristics.

Study on Dispersion, Adsorption, and Hydration Effects of Polycarboxylate Superplasticizers with Different Side Chain Structures in Reference Cement and Belite Cement.

To investigate the effects of Reference cement (RC) and Belite cement (LC) systems, different molecular structures of polycarboxylate ether (PCE) were prepared through the free radical polymerization reaction and designated as PC-1 and PC-2. The PCE was characterized and tested using a particle charge detector, gel permeation chromatography, a rotational rheometer, a total organic carbon analyzer, and scanning electron microscopy. The results showed that compared to PC-2, PC-1 exhibited higher charge density and better molecular structure extension, with smaller side-chain molecular weight and molecular volume. PC-1 demonstrated enhanced adsorption capacity in cement, improved initial dispersibility of cement slurry, and a reduction in slurry yield stress of more than 27.8%. LC, with its higher C2S content and smaller specific surface area compared to RC, could decrease the formation of flocculated structures, resulting in a reduction in slurry yield stress of over 57.5% and displaying favorable fluidity in cement slurry. PC-1 had a greater retarding effect on the hydration induction period of cement compared to PC-2. RC, which had a higher C3S content, could adsorb more PCE, leading to a greater retarding effect on the hydration induction period compared to LC. LC and PC-2, on the other hand, exhibited inhibition during the hydration acceleration period. The addition of PCE with different structures did not significantly affect the morphology of hydration products in the later stage, which was consistent with the trend of KD variation. This indicates that the analysis of hydration kinetics can better reflect the final hydration morphology.

Toward an understanding of the effects of nanocellulose during the free-radical polymerization reactions. Kinetic aspects of suspension-free radical polymerization of methyl methacrylate (MMA) in the presence and absence of nanocellulose

Toward an understanding of the effects of nanocellulose during the free-radical polymerization reactions. Kinetic aspects of suspension-free radical polymerization of methyl methacrylate (MMA) in the presence and absence of nanocellulose

In Situ Polyaniline Immobilized ZnO Nanorods for Efficient Adsorptive Detoxification of Cr (VI) from Aquatic System

The elimination of toxic heavy metal ions from wastewater has been found to be of great importance in human as well marine animal wellbeing. Among various heavy metals, Cr (VI) has been found to be one of the highly toxic and carcinogenic heavy metals which are found to be dissolved in the water stream, the urgent treatment of which needs to be a priority. The present study demonstrates the fabrication of zinc oxide nanorods (ZnO NRs) and an immobilized polyaniline nanorod (ZnO@PAni NR) composite through an in situ free radical polymerization reactions. The material synthesis and purity were verified by X-ray diffractometer (XRD), Fourier transform infrared (FTIR), scanning electron microscope (SEM), energy dispersive spectroscope (EDS), and transmission electron microscope (TEM). Further, ZnO@PAni NRs were applied as an adsorbent for Cr (VI) in the aquatic system and exhibited a tremendous removal efficiency of 98.76%. The impact of operating parameters such as dose effect and pH on adsorption properties were studied. The uptake mechanism of Cr (VI) by ZnO@PAni was best explained by pseudo-second-order reaction, which suggested that the adsorption of Cr (VI) by the synthesized adsorbent material was processed by chemisorption, i.e., through formation of chemical bonds. The adsorption process proved viable and endothermic thermodynamically, and best supported by a Langmuir model, suggesting a monolayer formation of Cr (VI) on the surface of ZnO@PAni NRs.

A tough and mechanically stable adhesive hydrogel for non-invasive wound repair.

Wound healing has been a great challenge throughout human history. Improper treatment for wounds is so easy to lead to infection and a series of serious symptoms, even death. Because of the ability of absorbing fluid and keeping a moist environment, the hydrogel with 3D networks is ideal candidate for wound dressing. More important, it has good biocompatibility. However, most of the hydrogel dressings reported have weak mechanical properties and adhesion properties, which greatly limit their clinical application. Herein, a tough adhesive hydrogel with good mechanical stability for non-invasive wound repair is reported. The hydrogel is composed of polyethylene glycol dimethacrylate (PEGDA), chitosan (CS) and chitin nano-whisker (CW). PEGDA and CS form interpenetrating network hydrogel through free radical polymerization reaction under the UV light. The introduction of CW further enhances the toughness of the hydrogel. The pH-sensitive CS can form adhesion to various materials through topological adhesion. As a wound closure repair material, PEGDA/CS/CW hydrogel not only has the characteristic of effectively closing the wound, defending against invading bacteria, and keeping the wound clean, but also has good tensile and mechanical stability, which is expected to realize the closure and repair of joints and other moving parts of the wound. This adhesive hydrogel is proven a promising material for wound closure repair.

Combined Catalysis: A Powerful Strategy for Engineering Multifunctional Sustainable Lignin-Based Materials

The production and engineering of sustainable materials through green chemistry will have a major role in our mission of transitioning to a more sustainable society. Here, combined catalysis, which is the integration of two or more catalytic cycles or activation modes, provides innovative chemical reactions and material properties efficiently, whereas the single catalytic cycle or activation mode alone fails in promoting a successful reaction. Polyphenolic lignin with its distinctive structural functions acts as an important template to create materials with versatile properties, such as being tough, antimicrobial, self-healing, adhesive, and environmentally adaptable. Sustainable lignin-based materials are generated by merging the catalytic cycle of the quinone-catechol redox reaction with free radical polymerization or oxidative decarboxylation reaction, which explores a wide range of metallic nanoparticles and metal ions as the catalysts. In this review, we present the recent work on engineering lignin-based multifunctional materials devised through combined catalysis. Despite the fruitful employment of this concept to material design and the fact that engineering has provided multifaceted materials able to solve a broad spectrum of challenges, we envision further exploration and expansion of this important concept in material science beyond the catalytic processes mentioned above. This could be accomplished by taking inspiration from organic synthesis where this concept has been successfully developed and implemented.