Three-dimensional Cross-linked Network Research Articles

A metal-organic framework-based electrocatalytic membrane boosts redox kinetics of lithium‑sulfur batteries

The shuttle behavior and sluggish conversion kinetics of polysulfides significantly impede the commercialization of lithium‑sulfur (LiS) batteries. Herein, we report a membrane-based electrocatalytic interlayer that consists of metal-organic framework (MOF) Co-ZIF-9 sheets and carbon nanotubes (CNT) for these issues, which is facilely weaved by vacuum filtration. The fully exposed active sites of ZIF-9 sheets endow this interlayer an efficient anchoring ability towards polysulfides, therefore efficaciously suppressing the polysulfides shuttle, and, more importantly, a strong electrocatalytic effect to accelerate the redox kinetics. Meanwhile, the three-dimensional cross-linked network structured by the conductive CNT and MOF material favours a rapid ion and electron transport, and the full utilization of adsorption and catalytic sites. As a consequence, this interlayer exhibits an excellent rate performance (a capacity up to 817 mAh g−1 under 5 C), an exceptional cyclic stability (a tiny decay of 0.019% for 1000 cycles at 1 C) and a distinctive high‑sulfur loading performance (7.2 mg cm−2) under a reduced electrolyte content. This study provides inspirations for the rational design of MOF-based nanostructures that can validly anchor polysulfides and catalyze their conversion for high-powered LiS batteries.

PH Sensitive Hydrogel: A Review

Hydrogels are three-dimensional cross-linked networks of polymer chains that can absorb and hold lots of water in the interstitial spaces between chains. Improving the safety efficacy ratio of existing drugs is a current challenge to be addressed rather than the development of novel drugs which involves much expense and time. The efficacy of drugs is affected by several factors such as their low aqueous solubility, unequal absorption along the gastrointestinal (GI) tract, risk of degradation in the acidic milieu of the stomach, low permeation of the drugs in the upper GI tract, systematic side effects, etc. This review aims to enlighten readers on the role of pH-sensitive hydrogels in drug delivery, their mechanism of action, swelling, and drug release as a function of pH change along the GI tract. The basis for the selection of materials, their structural features, physical and chemical properties, the presence of ionic pendant groups, and the influence of their pKavalues on the ionization, consequent swelling, and targeted drug release are also highlighted.

Unraveling the New Perspectives on Antimicrobial Hydrogels: State-of-the-Art and Translational Applications.

The growing impact of infections and the rapid emergence of antibiotic resistance represent a public health concern worldwide. The exponential development in the field of biomaterials and its multiple applications can offer a solution to the problems that derive from these situations. In this sense, antimicrobial hydrogels represent a promising opportunity with multiple translational expectations in the medical management of infectious diseases due to their unique physicochemical and biological properties as well as for drug delivery in specific areas. Hydrogels are three-dimensional cross-linked networks of hydrophilic polymers that can absorb and retain large amounts of water or biological fluids. Moreover, antimicrobial hydrogels (AMH) present good biocompatibility, low toxicity, availability, viscoelasticity, biodegradability, and antimicrobial properties. In the present review, we collect and discuss the most promising strategies in the development of AMH, which are divided into hydrogels with inherent antimicrobial activity and antimicrobial agent-loaded hydrogels based on their composition. Then, we present an overview of the main translational applications: wound healing, tissue engineering and regeneration, drug delivery systems, contact lenses, 3D printing, biosensing, and water purification.

Fungal Ligninolytic Enzymes and Their Application in Biomass Lignin Pretreatment.

Lignocellulosic biomass is a significant source of sustainable fuel and high-value chemical production. However, due to the complex cross-linked three-dimensional network structure, lignin is highly rigid to degradation. In natural environments, the degradation is performed by wood-rotting fungi. The process is slow, and thus, the use of lignin degradation by fungi has not been regarded as a feasible technology in the industrial lignocellulose treatment. Fungi produce a wide variety of ligninolytic enzymes that can be directly introduced in industrial processing of lignocellulose. Within this study, screening of ligninolytic enzyme production using decolorization of ABTS and Azure B dyes was performed for 10 fungal strains with potentially high enzyme production abilities. In addition to standard screening methods, media containing lignin and hay biomass as carbon sources were used to determine the change in enzyme production depending on the substrate. All selected fungi demonstrated the ability to adapt to a carbon source limitation; however, four strains indicated the ability to secrete ligninolytic enzymes in all experimental conditions-Irpex lacteus, Pleurotus dryinus, Bjerkandera adusta, and Trametes versicolor-respectively displayed a 100%, 82.7%, 82.7%, and 55% oxidation of ABTS on lignin-containing media and 100%, 87.9%, 78%, and 70% oxidation of ABTS on hay-containing media after 168 h of incubation. As a result, the most potent strains of fungi were selected to produce lignocellulose-degrading enzymes and to demonstrate their potential application in biological lignocellulose pretreatment.

Controlled Preparation of Cross-Linked SnO2 Hollow Nanotube Networks for Electrocatalytic CO2 Reduction

The electrochemical system based on water, CO2, and electricity is the key technology to realize the coexistence and combination of renewable energy and fossil energy, which can convert CO2 molecules into high-value-added products under mild and controlled conditions, thus achieving carbon neutrality. Designing efficient electrocatalysts to realize highly active, selective, and stable CO2RR has become one of the vital issues. Particularly, the nanostructure design and interface adjustment of electrocatalysts have been regarded as the key points for improving their catalytic performance. Herein, a tin dioxide hollow nanotube (SnO2 HNT) catalyst with a three-dimensional cross-linked network structure has been fabricated by electrospinning and rapid-heating calcination. The morphology and component structure of SnO2 HNTs were analyzed by a series of characterizations. The performance in electrocatalytic carbon dioxide reduction reaction (eCO2RR) was further tested. Owing to the hollow nanostructure, the catalyst possessed a large specific surface area and abundant active sites, which greatly accelerated mass transport and electron mobility. During eCO2RR, SnO2 HNTs achieved a peak faraday efficiency value of 87.4% for C1 products at −1.1 V vs RHE, which significantly suppressed the occurrence of hydrogen evolution side reactions. In addition, compared with the commercial SnO2 nanoparticles or partially reduced Sn/SnO2, the catalytic activity and selectivity of CO2-to-formate conversion significantly increased under the same potential, indicating that the optimization of electronic/geometric structure for high-yield metal oxides can effectively improve the comprehensive performance of eCO2RR.

In situ crosslink polymerization induced long-lived multicolor supramolecular hydrogel based on modified β-cyclodextrin

The construction of hydrogels with good mechanical properties and phosphorescent properties is full of challenges. Herein, we report a supramolecular phosphorescent hydrogel with long lifetime, high tensile strength and self-healing property, which can be easily constructed through in-situ thermal-initiated polymerization of isocyanatoethyl acrylate-modified β-cyclodextrin (β-CD-DA) and acrylate-modified adamantane (Ad-DA), acrylic acid (AA), followed by the non-covalent association with carbon dots (CNDs). The lifetime of phosphorescent hydrogel can reach 1261 ms at room temperature, and the quantum yield is 11%. Importantly, through the efficient triplet to singlet Förster resonance energy transfer (TS-FRET), the phosphorescent hydrogel shows the good phosphorescence energy transfer property for organic dyes Rhodamine B and Eosin Y with the delayed fluorescence lifetime up to 730 ms and 585 ms as well as the energy transfer efficiency (ΦET) up to 99.9% and 99.3%, respectively. Moreover, owing to the host-guest interactions between β-CD-DA and Ad-DA, the three-dimensional cross-linked network phosphorescent hydrogel can be easily stretched to 18 times of its original length, and can achieve self-healing of the cut surfaces within 30 min. These results will expand the scope of phosphorescent materials and provide new ideas and opportunities for materials science.

Core-shell FeCo@carbon nanocages encapsulated in biomass-derived carbon aerogel: Architecture design and interface engineering of lightweight, anti-corrosion and superior microwave absorption

The development of multifunctional microwave absorbing materials for practical applications in complex environments is a challenging research hotspot. Herein, the core–shell structure FeCo@C nanocages were successfully anchored on the surface of biomass-derived carbon (BDC) from pleurotus eryngii (PE) via freeze-drying and electrostatic self-assembly process, achieving lightweight, anti-corrosive, and excellent absorption properties. The superior versatility benefits from the large specific surface area, high conductivity, three-dimensional cross-linked networks, and appropriate impedance matching characteristics. The as-prepared aerogel realizes a minimum reflection loss (RLmin) of −69.5 dB with a corresponding effective absorption bandwidth (EAB) of 8.6 GHz at 2.9 mm. Simultaneously, the computer simulation technique (CST) further proves that the multifunctional material can dissipate microwave energy in actual applications. More importantly, the special heterostructure of aerogel endows excellent resistance to acid, alkali, salt medium, allowing potential applications of the microwave absorbing materials under complex environmental conditions.

Rheological and Aging Properties of Vegetable Oil-Based Polyurethane (V-PU) Modified Asphalt.

To study the rheological and aging properties of vegetable oil-based polyurethane (V-PU) modified asphalt, V-PU terminated with an -NCO group was synthesized from renewable castor oil, and liquefied MDI-100LL and 10-40 wt% V-PU modified asphalts were prepared. Temperature classification, multiple stress creep recovery (MSCR), and linear amplitude scanning (LAS) tests were carried out. The results showed that the modulus, the creep recovery rate (R), and the yield stress and yield strain of the V-PU modified asphalts significantly increased in the order: 0 wt% < 10 wt% < 20 wt% < 40 wt% < 30 wt%, while the phase angle and the unrecoverable creep compliance (Jnr) changed in the opposite order, and the high temperature grade of 30 wt% V-PU modified asphalt was 4 grades higher than that of the base asphalt, which indicated that the addition of V-PU enhanced the fatigue, permanent deformation, and recovery deformation resistance. The 30 wt% sample exhibited phase inversion had the best performance. Comprehensive FTIR, GPC, and fluorescence microscopy analyses showed that the molecular weight significantly increased and the V-PU molecules agglomerated after aging. The excess -NCO groups of V-PU prepolymer react with water in the air and the active hydrogen in the asphalt system and finally form a cross-linked three-dimensional network structure with the asphalt to improve performance. The mechanism of intramolecular cementation reaction and the aging process of V-PU modified asphalt was creatively derived.

Preparation of Nanocellulose Whisker/Polyacrylamide/Xanthan Gum Double Network Conductive Hydrogels

Hydrogels’ poor mechanical and recovery characteristics inhibited their application as a plastic deformable three-dimensional cross-linked network polymer with electrical properties for intelligent sensing and human motion detection. Cellulose has also been added to the hydrogel to enhance its mechanical properties. The hydrogel has been enhanced this way, and the double-network hydrogel has superior recovery and mechanical capabilities. This study used the traditional free radical polymerization method to prepare double-mesh hydrogels, with polyacrylamide as the backbone network, xanthan gum double-helix structure, and Al3+ complex structure as the second cross-linked network, and endowing the hydrogels with good mechanical recovery and mechanical properties. Adding cellulose nanowafers (CNWs) improved the mechanical properties of the hydrogels. The hydrogel could detect body movements and various postures in the same environment. Moreover, the hydrogel has excellent recovery, mechanical properties, and tensile strain; the maximum fracture stress is 0.14 MPa, and the maximum strain is 707.1%. In addition, Fourier infrared spectroscopy (FTIR) of xanthan gum and Xanthan gum—Al3+ were analyzed, and thermogravimetric analysis (TGA) and LCR bridge were used to analyze the properties of hydrogels. Notably, hydrogel-based wearable sensors have been successfully constructed to detect human movement. Its mechanical properties, sensitivity, and wide range of properties make hydrogel a great potential for various applications in wearable sensors.

Integrated design of multifunctional all-in-one polymer electrolyte membranes with 3D crosslinking networks toward high-performance lithium metal batteries

Gel polymer electrolytes (GPEs) are highly worthwhile for constructing high-energy-density lithium metal batteries (LMBs) because of their good flexibility and manufacturability. But, it is still challenging to prepare GPEs with excellent electrochemical performance, good flame retardancy, and good compatibility with electrodes for safe and dendrite-free LMBs application. Herein, a well-designed GPE with three-dimensional (3D) crosslinking network containing –CN and -PO(OC2H5)2 functional groups (3D-ADCL) with synergistic effect is prepared via thermal-initiated in-situ polymerization. Concretely, the -PO(OC2H5)2 segment enhances the flame resistance of polymer electrolyte, and the –CN segment grants improved Li-ion conductivity. In addition, the 3D crosslinking networks in the whole LMBs are incredibly favorable for improving the physical stability of both polymer electrolyte membrane/electrode bulks and electrolyte/electrode interface. Furthermore, the 3D-ADCL-based polymer electrolyte (3D-ADCL-PE) demonstrates an enhanced Li-ion transference number (tLi+) of 0.58 because the –CN groups possess strong coordination with Li-ion and electrostatic repulsion with PF6− anion. It is also confirmed that the –CN group can enable the formation of stable Li3N-rich solid electrolyte interphase (SEI) and high-quality cathode electrolyte interphase (CEI) layers to inhibit Li dendrite growth and stabilize the LiFePO4 cathode, respectively. Consequently, the 3D-ADCL-PE based LiFePO4/Li cells exhibit a remarkable capacity of 106.4 mA h g−1 at 6 C-rate with a high capacity retention of 90.3% after long 1000 cycles.

Biodegradation of vulcanized rubber by a gut bacterium from plastic-eating mealworms

The disposal of vulcanized rubber waste is difficult due to the presence of three-dimensional crosslinking network structure. Here, we report that a bacterium Acinetobacter sp. BIT-H3, isolated from the gut of plastic-eating mealworm, can grow on and degrade vulcanized poly(cis-1,4-isoprene) rubber (vPR). Scanning electronic microscopy (SEM) shows that strain BIT-H3 can penetrate into the vPR and produce craters and cracks. The tensile strength and the crosslink density of vPR decreased by 53.2% and 29.3% after ten weeks’ incubation, respectively. The results of Horikx analysis, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and X-ray absorption near-edge structure (XANES) spectroscopy reveal that strain BIT-H3 can break down both sulfide bridges and double bonds of polymeric backbone within vPR. Sulfate and oligo(cis-1,4 isoprene) with terminal aldehyde and keto groups were identified as metabolic products released during vPR degradation. Through genomic and transcriptional analyses, five enzymes of dszA, dszC1, dszC2, Laccase2147, and Peroxidase1232 were found to be responsible for vPR degradation. Based on the chemical structure characterizations and molecular analyses, a vPR biodegradation pathway was proposed for strain BIT-H3. These findings pave a way for exploiting vulcanized rubber-degrading microorganisms from insect gut and contribute to establish a biodegradation method for vulcanized rubber waste disposal.

Influence of Cross-Linking Conditions on Drying Kinetics of Alginate Hydrogel.

Hydrogels are three-dimensional cross-linked polymeric networks capable of a large amount of fluid retention in their structure. Hydrogel outputs manufactured using additive manufacturing technologies are exposed to water loss, which may change their original shape and dimensions. Therefore, the possibility of retaining water is important in such a structure. In this manuscript, kinetic analysis of water evaporation from sodium alginate-based hydrogels exposed to different environmental conditions such as different temperatures (7 and 23 °C) and ambient humidity (45, 50 and 95%) has been carried out. The influence of the cross-linking method (different calcium chloride concentration-0.05, 0.1 and 0.5 M) of sodium alginate and cross-linking time on the water loss was also considered. Studies have shown that a decrease in the temperature and increase in the storage humidity can have a positive effect on the water retention in the structure. The storage conditions that led to the least weight and volume loss were T 7 °C and 95% humidity. These experiments may help in selecting the appropriate hydrogel preparation method for future applications, as well as their storage conditions for minimum water loss and, consequently, the least change in dimensions and shape.

Plasmonically Active Supramolecular Polymer–Metal–Organic Framework Hydrogel Nanocomposite for Localized Chemo-photothermal Therapy

Hydrogels are a three-dimensional cross-linked network of hydrophilic polymers, extensively used for biomedical, biotechnological, and pharmaceutical applications. The functionality of hydrogels could be enhanced by synthesizing hydrogel nanocomposites that can both enable controlled release of drugs in a cancerous microenvironment and near-infrared-induced localized heat generation for combined chemo-photothermal therapy (chemo-PTT), a potent anticancer therapeutic approach. Herein, we developed a plasmonically active hydrogel with carboxymethyl chitosan (CMC) as the supporting matrix cross-linked with ZIF8 nanoparticles and Mg2+. The ZIF8 nanoparticles were loaded in situ with ultrasmall gold nanoparticles (UsGNPs) and an anticancer drug curcumin for localized chemo-PTT. The plasmonic hydrogel (PHG) showed viscoelastic and self-healing properties governed by the supramolecular interaction between ZIF8 and CMC. The injectable PHG exhibited a photothermal conversion efficiency of ∼41%. Chemo-PTT with Cur-PHG effectively inhibited 4T1 breast cancer under both in vitro and in vivo conditions. The biocompatible PHG was found to release UsGNPs from tumor tissues post intratumoral injection followed by predominant distribution in the liver and kidney. Due to the size of UsGNPs (<5 nm), they were consistently detected in urine over the period of treatment confirming the overall degradable nature of PHG that delivers a localized outcome with negligible systemic toxicity.

A semi-interpenetrating network-based microneedle for rapid local anesthesia

To improve the mechanical strength of a polyvinylpyrrolidone (PVP K29/32)-derived dissolvable microneedle, a semi-interpenetrating network is developed using covalently crosslinked methacrylated chondroitin sulfate (CS-MA) in combination with PVP K29/32, which is used to successfully load lidocaine hydrochloride (LIDH) and applied as a microneedle patch for rapid local anesthesia. Specifically, CS-MA when mixed with soluble PVP and photo initiators afforded a covalently cross-linked three-dimensional network (CS-MA/PVP MN) after irradiation at 405 nm for 1 min. CS-MA/PVP MNs demonstrated greatly enhanced mechanical strength and reduced moisture absorption rate as compared to PVP MN. The content of LIDH in each microneedle array was determined as 802.8 ± 22.8 μg. The obtained CS-MA/PVP MNs displayed sharp needle edges with a uniform appearance under scanning electron microscope. Penetration studies showed that the prepared microneedles were able to penetrate the skin of experimental animals causing minimum irritation. The biosafety study showed that the trauma to the skin was almost negligible after the application of microneedles. Furthermore, preliminary pharmacodynamic studies in guinea pigs revealed the prepared microneedles achieved a rapid onset of action (<1 min) compared to the commercially available lidocaine cream (about 1 h). Overall, LIDH-loaded semi-interpenetrating network-based microneedles serve as a promising transdermal delivery platform for achieving rapid and efficient local anesthesia.

Hyperbranched Polymer Network Based on Electrostatic Interaction for Anodes in Lithium-Ion Batteries.

Silicon is considered as one of the ideal anode materials for the new generation of lithium-ion batteries due to its extremely high theoretical specific capacity. Nevertheless, in the actual charging and discharging process, the Si electrode will lose its electrochemical performance due to the huge volume change of Si nanoparticles resulting in detachment from the surface of the fluid collector. The polymer binder can bond the Si nanoparticles together in a three-dimensional cross-linking network, which can thus effectively prevent the Si nanoparticles from falling off the surface of the fluid collector due to the drastic change of volume during the charging and discharging process. Therefore, this study developed a new polymer binder based on electrostatic interaction with hyperbranched polyethylenimine (HPEI) as the main body and water-soluble carboxylated polyethylene glycol (CPEG) as the cross-linker, where the degree of cross-linking can be easily optimized by adjusting the pH value. The results demonstrate that, when the density of positive and negative charges in the binder is relatively balanced at pH 7, the stability of the battery's charge-discharge cycle is significantly improved. After 200 cycles of constant current charge-discharge test, the specific capacity retention rate is 63.3%.

PAAS-β-CDp-PAA as a high-performance easily prepared and water-soluble composite binder for high-capacity silicon anodes in lithium-ion batteries

The hyperbranched hydroxyl-rich water-soluble β-cyclodextrin polymer (β-CDp) is synthesized by the reaction between β-cyclodextrin and 1, 4-butanediol diglycidyl ether with a facile and environmentally friendly method, which is systematically confirmed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric (TG). A water-soluble PAAS-β-CDp-PAA binder is prepared by the esterification reaction between partially neutralized sodium polyacrylate (PAAS), β-CDp, and polyacrylic acid (PAA). Moreover, the optimized PAAS6-β-CDp1-PAA3 binder, with a three-dimensional (3D) cross-linked network structure constructed by covalent bonds, hydrogen bonds, and electrostatic interactions, displays a stronger adhesion between the active material and the current collector, effectively promotes the diffusion of Li+, and maintains the structural integrity of the electrode during charge-discharge cycling. Thus Si/PAAS6-β-CDp1-PAA3 electrode exhibits a higher initial discharge specific capacity of 3869 mAh g−1 with a columbic efficiency of 89.79% at 200 mA g−1, and a discharge specific capacity of 2513 mAh g−1 with a capacity retention rate of 71.10% is achieved after 100 cycles.

Preparation and action mechanism of temperature sensitive N-isopropylacrylamide/nanosilica hybrid as rheological modifier for water-based drilling fluid

A temperature-sensitive silica nanohybrid with a temperature response at 35 °C was prepared by copolymerization of temperature-sensitive monomer N-isopropylacrylamide (NIPAM) with reactive nanosilica (RNS-D).The rheological properties of the as-prepared NIPAM/nano-SiO2 nanohybrid as the rheological modifier of water-based drilling fluid were tested. Findings demonstrate that NIPAM/nano-SiO2 nanohybrid contributes to increasing the viscosity of the drilling fluid upon elevating temperature, and the drilling fluid fits to the Herschel-Bulkley model. The drilling fluid containing 1.0% (mass fraction) of NIPAM/nano-SiO2 nanohybrid exhibits significant thermally thickening performance at the critical association temperature (Tass) of NIPAM (Tass; 35 °C). In terms of the action mechanism of NIPAM/nano-SiO2 nanohybrid in drilling fluid, the amide group of NIPAM/nano-SiO2 nanohybrid can form hydrogen bond with bentonite, thereby being well adsorbed on the surface and edge of bentonite platelets or even entrapped into the interlay of the bentonite platelets. The resultant cross-linked structure can function to prevent the flocculation of bentonite platelets and increase the viscosity of the drilling fluid. After heating to Tass, the temperature-sensitive polymer molecular chains undergo hydrophilic to hydrophobic transformation and hydrophobic association to form cross-linked three-dimensional network structure and increase the viscosity of the drilling fluid. More importantly, the water-based drilling fluid with 1.0% NIPAM/nano-SiO2 nanohybrid still retains thermally thickening behavior and flat rheology even after being aged at 150 °C. Therefore, the temperature-sensitive NIPAM/nano-SiO2 nanohybrid could be a potential rheological modifier for flat rheology water-based drilling fluid.

Methylcellulose/lignin biocomposite as an eco-friendly and multifunctional coating material for slow-release fertilizers: Effect on nutrients management and wheat growth

To obviate adverse effects from the non-biodegradability of certain polymer-based slow-release fertilizers (SRFs) and to offset higher operational costs, the use of biopolymers as coating material has recently caught interest in the research circles. The present work aims to design a sustainable coating material based on biodegradable polymers. To this end, Alfa plant was initially exploited as a viable sustainable source for the extraction of lignin (LGe), which was in turn integrated into the development of a three-dimensional cross-linked network, including methylcellulose (MC) as a matrix and citric acid (CA) as a cross-linking agent. Then, the designed coating material was applied onto Di-ammonium Phosphate (DAP) and Triple Superphosphate (TSP) water-soluble fertilizers in a rotating pan machine. Chemical, physical, and biodegradation studies have confirmed that the coating material is environmentally-friendly. Nutrients release experiments in water as well as in soil environments have proved the effectiveness of the MC and MC/LGe coating layers in delaying the nutrients discharge. Besides, the nutrients release from coated DAP and TSP lasted longer than 30 days. Furthermore, the coating film enhanced the fertilizers mechanical resistance and boosted the soil water retention capacity. The agronomic evaluation has also confirmed their remarkable potential in enhancing wheat leaf area, chlorophyll content and biomass, in addition to the roots architecture and the final fruiting efficiency. These results showed that this hybrid composite could be used as an efficient coating material to produce slow-release fertilizers with multifunctional performances.

Highly Stretchable Fatty Acid Chain-Dangled Thermoplastic Polyurethane Elastomers Enabled by H-Bonds and Molecular Chain Entanglements

Thermoplastic polyurethane (TPU) elastomers are widely used in daily products owing to their flexible structures and decent mechanical properties. Vegetable oils (VOs) are promising renewable resources for polymer synthesis with readily availability and abundant derivatives. However, most VO-based polyurethanes are usually thermosets with an unsatisfactory material performance because the C═C bonds are randomly located on triglyceride long chains. Herein, a biobased TPU elastomer was facilely synthesized from palm oil (PO) with desirable and tunable mechanical properties. PO-based diol was synthesized from PO via amidation with 2-(2-hydroxyethylamino)ethanol. The resulting PO diethanolamide (POEA), combined with biobased butane-1,4-diol, was further reacted with 1,6-diisocyanatohexane to prepare PO-based TPU elastomers. The elastomers containing abundant H-bonds from carbamates in the backbone and dangling fatty acid side chains exhibited a microphase separation structure, endowing the elastomers with superior stretchability (up to a strain of 831%), restorability, and self-healing ability. The morphological, melting, crystallization, and rheological behaviors of the elastomers were fully studied. The dynamic and reversible three-dimensional cross-linked network consisting of van der Waals forces and H-bonds was investigated to reveal the formation mechanism of the elastomers.

Polybenzoxazine aerogels created in Lewis acid catalysis for thermal insulation matrix in deep space exploration

Polybenzoxazine aerogel is a new polymer aerogel material developed in recent years, which the ring-opening polymerization of benzoxazine monomer under high temperature or HCl could achieve the formation of cross-linked three-dimensional network structure so that to further reduce the cost of preparation. However, HCl as a catalyst has the disadvantages of easy volatilization and corrosion. Here we introduced Lewis acid as the catalyst for fabricating nanoporous polybenzoxazine aerogels with low density and self-extinguishing properties depending upon the evolution law for the influence of the mixed ratio of Lewis acid and hydrochloric acid (volume ratio) on the corresponding aerogels. The results show that PBz aerogels prepared in the mixed acid environment (with n-hexane as the exchange solvent) have a good three-dimensional nanopore network structure, and the pore size distribution is in the range of 20–140 nm. Additionally, the obvious self-extinguishing performance (even exposing to a flame at 1200 °C), low density and excellent mechanical properties are reflected as well, potentially suggesting the broad application prospects in the field of aerospace.