Dual-crosslinked Network Research Articles

Recyclable and mechanically tough nanocellulose reinforced natural rubber composite conductive elastomers for flexible multifunctional sensor

The development of flexible wearable multifunctional electronics has gained great attention in the field of human motion monitoring. However, developing mechanically tough, highly stretchable, and recyclable composite conductive materials for application in multifunctional sensors remained great challenges. In this work, a mechanically tough, highly stretchable, and recyclable composite conductive elastomer with the dynamic physical-chemical dual-crosslinking network was fabricated by the combination of multiple hydrogen bonds and dynamic ester bonds. To prepare the proposed composite elastomers, the polyaniline-modified carboxylate cellulose nanocrystals (C-CNC@PANI) were used as both conductive filler to yield high conductivity of 15.08 mS/m, and mechanical reinforcement to construct the dynamic dual-crosslinking network with epoxidized natural rubber latex to realize the high mechanical strength (8.65 MPa) and toughness (29.57 MJ/m3). Meanwhile, the construction of dynamic dual-crosslinking network endowed the elastomer with satisfactory recyclability. Based on these features, the composite conductive elastomers were used as strain sensors, and electrode material for assembling flexible and recyclable self-powered sensors for monitoring human motions. Importantly, the composite conductive elastomers maintained reliable sensing and energy harvesting performance even after multiple recycling process. This study provides a new strategy for the preparation of recyclable, mechanically tough composite conductive materials for wearable sensors.

Trilayered biomimetic hydrogel scaffolds with dual-differential microenvironment for articular osteochondral defect repair

Commonly, articular osteochondral tissue exists significant differences in physiological architecture, mechanical function, and biological microenvironment. However, the development of biomimetic scaffolds incorporating upper cartilage, middle tidemark-like, and lower subchondral bone layers for precise articular osteochondral repair remains elusive. This study proposed here a novel strategy to construct the trilayered biomimetic hydrogel scaffolds with dual-differential microenvironment of both mechanical and biological factors. The cartilage-specific microenvironment was achieved through the grafting of kartogenin (KGN) into gelatin via p-hydroxyphenylpropionic acid (HPA)-based enzyme crosslinking reaction as the upper cartilage layer. The bone-specific microenvironment was achieved through the grafting of atorvastatin (AT) into gelatin via dual-crosslinked network of both HP-based enzyme crosslinking and glycidyl methacrylate (GMA)-based photo-crosslinking reactions as the lower subchondral bone layer. The introduction of tidemark-like middle layer is conducive to the formation of well-defined cartilage-bone integrated architecture. The in vitro experiments demonstrated the significant mechanical difference of three layers, successful grafting of drugs, good cytocompatibility and tissue-specific induced function. The results of in vivo experiments also confirmed the mechanical difference of the trilayered bionic scaffold and the ability of inducing osteogenesis and chondrogenesis. Furthermore, the articular osteochondral defects were successfully repaired using the trilayered biomimetic hydrogel scaffolds by the activation of endogenous recovery, which offers a promising alternative for future clinical treatment.

Development of dual-crosslinked nanocomposite gel for water management in high-temperature reservoirs

Due to their controllable gelation time and high gel strength, polymer gels are widely used in the oil and natural gas industry for sealing operations. Aiming at the problems of fast gelation time and poor stability of polymer gel when the temperature exceeds 120 °C, a dual-crosslinked nanocomposite gel for high-temperature reservoir water management was developed. Polymers, crosslinking agents, nanomaterials, and retarders were studied for the effects of the concentration of each component on the initial viscosity, gelation time, stability, and viscoelastic properties of the gel. The long-term stability and water-plugging adaptability were evaluated. FTIR and viscoelastic performance analyses clarified the mechanism of action. The gel strength and thermal stability enhancement mechanism was analyzed based on SEM. At 170 °C,the gelation time is 5 ∼ 10h after adding retarder and aging in formation water for 30 days resulted in dehydration rates within 10%. The injection volume of the plugging agent is 0.3 PV, and the plugging rate of sand-filled pipes with different permeability is above 97%. The elastic modulus of the terpolymer SAV333/phenol-formaldehyde system was increased by 10 times by resorcinol and SiO2. The enhancement mechanism is mainly due to the gel’s strong dendritic dual-crosslinked network structure and the dual role of hydrogen bonding and electrostatic attraction of SiO2. Dual-crosslinked nanocomposite gel (DCNG) has shown promising performance as sealing material in high-temperature and ultra-high-temperature reservoirs.

Dual Cross-Linked Stimuli-Responsive Alginate-Based Hydrogels.

Sodium alginate with different molecular weights (55, 170, and 320 kg mol-1) were chemically modified by grafting methacrylic moieties onto the hydroxyl groups of the alginate backbone. The methacrylation was optimized to obtain different degrees of modification. Chemically cross-linked hydrogels were obtained following UV-light irradiation in the presence of a photoinitiator. The swelling behavior and the mechanical properties were observed to depend on both the degree of methacrylation and the alginate molecular weight. Due to the chain entanglement present in high-viscosity sodium alginate, lower degrees of modification were required to tune the hydrogel properties. Moreover, in the presence of Ca2+, secondary cross-linking was introduced by the coordination of the alginate guluronate moieties with the Ca2+ ions. The addition of this secondary cross-linking caused fast volume shrinkage and a reinforcement of the mechanical properties. The secondary cross-linking was reversible, and the hydrogels regained their original shape for at least three cycles. Additionally, the dual cross-linked network can be used to induce adhesion between hydrogels and serve as a building block for self-folding actuators.

Preparation and characterization of peach gum/chitosan polyelectrolyte composite films with dual cross-linking networks for antibacterial packaging

Peach gum (PG) is a valuable polymeric feedstock for developing eco-friendly, bio-safe, and functional materials. However, PG has limited use in food packaging due to its inferior mechanical and antibacterial properties. To overcome these limitations, we created a dual cross-linked network by introducing chitosan (CS) and glycerol to the PG matrix. Our research discovered that incorporating CS into the PG matrix significantly improved its Young's modulus, from 277.62 to 925.89 MPa, and its tensile strength from 5.96 to 39.94 MPa. Furthermore, the inclusion of glycerol greatly increased the elongation. These enhancements were attributed to the ionic and hydrogen-bonding interactions between the two biopolymers. Additionally, the composite films exhibited strong antibacterial effects, reducing the total number of colonies by 99.2 % and 99.9 % against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively. The incorporation of CS resulted in more amorphous films, enhancing their stiffness, flexibility, and barrier properties. To assess the practical application of PG/CS composite films, we conducted a comparative analysis between non-packaged strawberries and strawberries packaged with these films. The results demonstrated that the composite polyelectrolyte film extended the shelf life of strawberries better than the non-packaged fruits.

Secondary Chemical Cross-Linking to Improve Mechanical Properties in a Multifaceted Biocompatible Strain Sensor.

A new conductive and transparent organohydrogel is developed with high stretchability, excellent mechanical, self-healing, antifreezing, and adhesive properties. A simple one-pot polymerization method is used to create polyacrylamide cross-linked through N,N'-methylenebis(acrylamide) (MBAA) and divinylbenzene (DVB). The dual chemical cross-linked gel network is complemented by several physical cross-links via hydrogen bonding and π-π interaction. Multiple chemical and physical cross-links are used to construct the gel network that allows toughness (171 kPa), low modulus (≈45 kPa), excellent stretchability (>1100%), and self-healing ability. The use of appropriate proportions of the water/glycerol binary solvent system ensures efficient environment tolerance (-20 to 40 °C). Phytic acid is used as a conductive filler that provides excellent conductivity and contributes to the physical cross-linking. Dopamine is incorporated in the gel matrix, which endows excellent adhesive property of the gel. The organohydrogel-based strain sensors are developed with state-independent properties, highly linear dependence, and excellent antifatigue performance (>100 cycles). Moreover, during the practical wearable sensing tests, human motions can be detected, including speaking, smiling, and joint movement. Additionally, the sensor is biocompatible, indicating the potential applications for the next generation of epidermal sensors.

Fabrication of antimicrobial cationic hydrogels driven by physically and chemically crosslinking for wound healing

The wound therapy based on antibiotic delivery inevitably leads to the emergence of drug resistance. Hydrogel biomaterials with inherent antibacterial activities have emerged as promising candidates for addressing this issue. However, developing an inherently antibacterial hydrogel through simple and facile strategies to promote localized wound infection healing remains a challenge. In this study, we successfully constructed antimicrobial cationic hydrogels with self-healing and injectable properties through physically and chemically dual-crosslinked networks. The networks were formed by the copolymers poly[(di(ethylene glycol) methyl ether methacrylate)-co-(4-formylphenyl methacrylate)-co-(2-(methacryloyloxy)ethyl]trimethylammonium chloride solution)] (PDFM) and poly[(di(ethylene glycol) methyl ether methacrylate)-co-(2-aminoethyl methacrylate hydrochloride)-co-(2-(((6-(6-methyl-4[1H]pyrimidionylureido) hexyl)carbamoyl)oxy)ethyl methacrylate)] (PDAU). The hydrogel systems effectively facilitate the regeneration and healing of infected wounds through the contact bactericidal feature of quaternary ammonium cations. The presence of Schiff base bonds in the injectable hydrogels imparts remarkable pH responsiveness and self-healing properties. In vitro experiments verified their intrinsic antibacterial activities along with their favorable cytocompatibility and hemocompatibility in both in vitro and in vivo. In addition, the hydrogel significantly accelerated the healing of bacterially infected in a full-thickness skin wound. This facilely prepared dual-crosslinked hydrogel, without antibiotics loading, holds significant prospects for treating infected wounds.

Multifunctional films with superior mechanical performance, transparency, antibacterial properties enabled by a physical and chemical dual crosslinking network construction

Exploring sustainable and bio-degradable alternative materials based on lignin and cellulose is expected to address the serious environmental problems caused by the continuous accumulation of petroleum plastic waste. One open question is how to make a high mechanical strength lignin-cellulose material without optical haze. Herein, a multifunctional lignin-cellulose film with excellent mechanical properties and high transparency is successfully prepared based on Schiff base chemistry along with multiple hydrogen bonding interactions. Combined with the chemical and physical double cross-linking network, positively charged aminated lignin improves the compatibility with dialdehyde cellulose and also optimizes the internal structure of the material. Significantly, the obtained films (ALDC10) deliver exceptional mechanical properties (tensile strength, 164.8 MPa and Young's modulus, 12.1 GPa), which are higher than those of some commercial petroleum-based plastics. The films endow superior transparency, antimicrobial (>50 %), UV shielding, and water vapor barrier properties, making them suitable for plastics replacement in active food (apple) packaging. Additionally, the transparent films show photothermal conversion properties, which have high potential applications in food vending machine to delay spoilage of foods with reduced energy consumption. This work establishes advanced valorization of cellulose and lignin, with superior performance, which is expected to replace petroleum plastics in various applications.

Mechanically robust hydrogel from thermosetting polybenzoxazine with dual crosslinking network

The main chain of polymer composition in hydrogels is mostly aliphatic and the crosslinking density is usually low, which renders the hydrogels with low mechanical strength. In this work, a kind of thermosetting resin, benzoxazine is used as the starting material to prepare the corresponding hydrogels by one-pot synthesis. The organic gels are firstly formed in dimethylformamide with the aid of catalyst, followed by extraction of water to give the hydrogels. It is revealed that due to the presence of covalent crosslinking and abundant hydrogen bonding, the as-prepared rigid hydrogels show extremely high compressive strength. The hydrogel with 55.8 wt% of water shows yield strength about 20 MPa and sustains compressive strength of 75 MPa (compressive stress of 30 kN, compressive strain of 67 %) without cracking. The hydrogel also show extremely high dielectric constant of 392,000, dielectric loss of 971,000, and ionic conductivity of 1.7 × 10−3 S/m at 100 Hz. Moreover, the responsiveness to pH variation suggests its potential application as smart responsive materials. To show the superiority of preparing functional composite hydrogels using this strategy, electroconductive and magnetic fillers are introduced and the as-prepared composite hydrogels show good electromagnetic shielding performance.

Ultra-Tough and Highly Stretchable Dual-Crosslinked Eutectogel Based on Coordinated and Non-Coordinated Two Types Deep Eutectic Solvent Mixture.

Eutectogels are gaining attention in flexible device applications for their superior ionic conductivity, stability, biocompatibility, and cost-effectiveness. However, most existing eutectogels suffer from low strength and toughness. Herein, ultra-tough and highly stretchable polyacrylamide (PAM) eutectogels featuring a dual-crosslinked network comprising chemical cross-linking and physical cross-linking facilitated by metal coordination bonds and hydrogen bonds are developed. This is achieved through a controlled strategy involving polymerization of acrylamide in a coordinated metal salt-type deep eutectic solvent (DES) combined with a non-coordinated choline chloride (ChCl)-type DES mixture. By varying the molar ratio of these two types of DES, exceptional and adjustable mechanical properties of the resulting eutectogel are achieved, including a high tensile strength ranging from 2.9 to 8.2MPa and elongation at break ranging from 1725 to 747%, at a 70 wt% DES content. Furthermore, the reversible non-covalent crosslinking in these eutectogels enables self-recovery and self-healing capabilities of eutectogels. The prepared eutectogels also exhibit outstanding ionic conductivity (3.56 mS cm-1 ), making them well-suited for use as strain sensors in human motion detection. The toughening strategy is universally effective for creating tough eutectogels using coordinated metal salt-type DES with various metal ions, as well as a diverse range of coordinatable polymers.

Low-temperature strain-sensitive sensor based on cellulose-based ionic conductive hydrogels with moldable and self-healing properties

Bioelectronics based on high-performance conductive ionic hydrogels, which can create novel technological interfaces with the human body, have attracted significant interest from both academia and industry. However, it is still a challenge to fabricate hydrogel sensor with integration of good mechanical properties, fast self-healing ability and flexible strain sensitivity below 0 °C. In this paper, we present a moldable, self-healing and adhesive cellulose-based ionic conductive hydrogel with strain-sensitivity, which was prepared by forming dual-crosslinked networks using poly(vinyl alcohol) (PVA) with borax, calcium chloride (CaCl2), zinc chloride (ZnCl2) and 2,2,6,6-tetramethylpiperidine-1-oxyl oxidized cellulose nanofibril (TCNF). The hydrogel exhibited fast self-healing within 10 s, moderate modulus of 5.13 kPa, high elongation rate of 1500 % and excellent adhesion behavior on various substrates. Due to multiple hydrogen bonding and the presence of CaCl2 and ZnCl2, the hydrogel presented a reduced freezing point as low as −41.1 °C, which enabled its application as a low-temperature strain sensor. The proposed hydrogel provides a simple and facile method for fabricating multi-functional hydrogels that can be used as suitable strain sensors for applications such as wearable electronic sensor, soft robotics and electronic skins in a wide temperature range.

Cottonseed protein bioadhesive with high adhesion performance achieved by a synergistic dual-crosslinking strategy

Plant adhesives have great potential as substitutes for formaldehyde-based adhesives due to their environmental friendliness, low cost, and nontoxicity. However, the application of this type of adhesive is challenged by its water resistance. Herein, an environmentally friendly bioadhesive was prepared from biomaterials, including waste cottonseed protein and sawdust. Isophorone diisocyanate (IPDI) and oxidized cellulose (OC) were used as double crosslinking modifiers. A protein-based bioadhesive with excellent adhesive properties and stable hydrothermal resistance was produced. The impact of IPDI and OC on the crosslinking network was evaluated by detailed Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry analysis. It was found that IPDI and OC, as crosslinking agents, synergistically improved the dry and wet bonding strength of the adhesive. At the optimal loadings of 10% OC and 20% IPDI, the wet bonding strength of the adhesive reached 1.55 MPa on average, which is more than twice that of the Chinese Type II plywood adhesive standard (0.7 MPa). The dry bonding strength also increased to 2.67 MPa with this addition. The improvements in bonding strength as well as the water-resistance of the bioadhesive were ascribed to the formation of a dual-crosslinking network between the IPDI, OC, and cottonseed protein. Both protein-oxidized cellulose and protein-isophorone diisocyanate crosslinking networks were formed in the adhesive system, tightly combining the adhesive components. Thus, the biodegradable adhesive developed in this work provides an effective and convenient approach for the development of all-biomass-derived adhesives, and the constructed high-performance adhesive presents potential application for sustainable wood products.

Advancing high-performance tailored dual-crosslinking network organo-hydrogel flexible device for wireless wearable sensing

Conductive hydrogels are essential for enabling long-term and reliable signal sensing in wearable electronics due to their tunable flexibility, stimulus responsiveness, and multimodal sensing integration. However, developing durable and dependable integrated hydrogel-based flexible devices has been challenging due to mismatched mechanical properties, limited water retention capability, and reduced flexibility. This work addresses these challenges by employing a tailored physical–chemical dual-crosslinking strategy to fabricate dynamically reversible organo-hydrogels with high performance. The resultant organo-hydrogels exhibit exceptional characteristics, including high stretchability (up to ∼495% strain), remarkable toughness (with tensile and compressive strengths of ∼1350 kPa and ∼9370 kPa, respectively), and outstanding transparency (∼90.3%). Moreover, they demonstrate excellent long-term water retention ability (>2424 h, >97%). Notably, the organo-hydrogel based sensor exhibits heightened sensitivity for monitoring physiological signals and motions. Furthermore, our integrated wireless wearable sensing system efficiently captures and transmits various human physiological signals and motion information in real-time. This research advances the development of customized devices utilizing functional organo-hydrogel materials, making contributions to fulfilling the increasing demand for high-performance wireless wearable sensing.

Aldehyde modified cellulose-based dual stimuli responsive multiple cross-linked network ionic hydrogel toward ionic skin and aquatic environment communication sensors

Recently, materials with complicated environmentally-sensitive abilities, high stretchability and excellent conductive sensitivity are interesting actuators in future applications. Herein, we fabricated a versatile and facile polyvinyl alcohol/polyacrylic acid/dialdehyde cellulose nanofibrils-Fe3+ hydrogel integrated with programmable dual-shape memory properties, high mechanical strength, good recoverability, and heat-induced self-healing capability. Benefiting from the synergistic effect of hydrogen bonds and dual metal coordination bonds of cellulose-based dialdehyde and carboxyl with Fe3+and then heating-freeze-thawing cycle treatment, the obtained hydrogel exhibited dual shape memory abilities, high tensile strain (up to 600 %), good self-recovery, and anti-fatigue properties. Moreover, the resultant hydrogel sensors showed revealed high strain sensitivity (gauge factor = 2.95) and satisfactory electrochemical performance; and such hydrogel-based sensor could be used as ionic skin to detect various human motions in real-time and barrier-free communication in the aquatic environment. The composite hydrogel with superior and versatile performances reported in this study could offer a great promise to be applied under extreme conditions as multifunctional sensors.

Molecularly engineered dual-network photothermal hydrogel delivery system with enhanced mechanical properties, antibacterial ability and angiogenic effect for accelerating wound healing

Bacterial infection caused by trauma and chronic wounds in the most mobile area remains a challenge in clinic. It is difficult to achieve the synergistic effects of antibacterial capacity and skin regeneration using conventional therapeutic methods. Developing a multi-functional hydrogel dressing that can cope with the complex wound environment will contribute to the healing and therapeutic effects. In this work, a novel Cur@PAM/TA-Cu photothermal hydrogel delivery system was prepared by engineering tannic acid (TA) into covalent cross-linked polyacrylamide (PAM) on which the chelating tannic acid-copper metal–polyphenolic network (TA-Cu MPN) was imposed to form dual-crosslinked networks, and the natural medicine curcumin was loaded eventually. The molecularly engineered dual-crosslinked networks resulted in enhanced mechanical properties including bio-adhesion, tensile strength and self-healing, which made the hydrogel suitable for dynamic wound and various application scenarios. In addition, the excellent photothermal capacity, antioxidant effect and biocompatibility of the hydrogel were demonstrated. Notably, this curcumin loaded photothermal hydrogel exhibited superior antibacterial capacity (almost 100% killing ratio to E. coli and S. aureus) under 808 nm laser irradiation. Meanwhile, the in vivo wound healing experiment results revealed that the anti-inflammation and proangiogenic effect of Cur@PAM/TA-Cu hydrogel successfully shortened the healing time of wound and the reconstruction of skin structure and function. Thus, this dual-crosslinked multi-functional hydrogel delivery system is a promising wound dressing for accelerating wound healing.

Bio-Inspired Conductive Hydrogels with High Toughness and Ultra-Stability as Wearable Human-Machine Interfaces for all Climates.

Drawing inspiration from Salicornia, a plant with the remarkable ability to thrive in harsh environments, a conductive hydrogel with high toughness and ultra-stability is reported. Specifically, the strategy of pre-cross-linking followed by secondary soaking in saturated salt solutions is introduced to prepare the PAAM-alginate conductive hydrogel with dual cross-linked dual network structure. It allows the alginate network to achieve complete cross-linking, fully leveraging the structural advantages of the PAAM-alginate conductive hydrogel. The highest tensile strength of the obtained conductive hydrogel is 697.3kPa and the fracture energy can reach 69.59kJm-2 , significantly higher than human cartilage and natural rubbers. Specially, by introducing saturated salt solutions within the hydrogel, the colligative properties endow the PAAM-alginate conductive hydrogel with excellent water retention and anti-freezing properties. The prepared conductive hydrogels can work stably in an ambient environment for more than 7days and still maintain good mechanical behavior and ionic conductivity at -50°C. Benefiting from the excellent comprehensive performance of conductive hydrogels, wearable human-machine interfaces that can withstand large joint movements and are adapted for extreme environments are prepared to achieve precise control of robots and prostheses, respectively.

Self-strengthening and conductive cellulose composite hydrogel for high sensitivity strain sensor and flexible triboelectric nanogenerator

Triboelectric nanogenerators (TENGs) as promising energy harvesting devices have gained increasing attention. However, the fabrication of TENG simultaneously meets the requirements of green start feedstock, flexible, stretchable, and environmentally friendly remains challenging. Herein, the hydroxyethyl cellulose macromonomer (HECM) simultaneously bearing acrylate and hydroxyl groups was first synthesized and used as a crosslinker to prepare the chemically and physically dual-crosslinked cellulose composite hydrogel for an electrode material of stretchable TENG. Meanwhile, the in-situ polymerization of pyrrole endowed the hydrogel with satisfactory conductivity of 0.40 S/m. More impressively, the synergies of the cellulose rigid skeleton and the construction of the dual-crosslinking network significantly improved the mechanical toughness, and the hydrogel exhibited excellent self-strengthening through cyclic compression mechanical training, the self-strengthening efficiency reached 124.7 % after 10 compression cycles. Given these features, the hydrogel was used as wearable strain sensors with extremely high sensitivity (GF = 3.95) for real-time monitoring human motions. Additionally, the hydrogel showed practical applications in stretchable H-TENG for converting mechanical energy into electric energy to light LEDs and power a digital watch, and in self-powered wearable sensors to distinguish human motions and English letters. This work provided a promising strategy for fabricating sustainable, eco-friendly energy harvesting and self-powered electronic devices.

Ultrafast and facile construction of programmable, multidimensional wrinkled-patterned polyacrylamide/sodium alginate hydrogels for human skin-like tactile perception

Customizable structures and patterns are becoming powerful tools for biomimetic design and application of soft materials. The construction of long-range ordered self-wrinkled structures on multi-dimensional and complex-shaped surfaces with facile, fast and efficient strategies still faces serious challenges. During the stretch-recovery process, the carboxyl groups in the polyacrylamide/sodium alginate dual network gel form robust coordination with Fe3+ to achieve a hard shell layer, resulting in a modulus mismatch between the inner soft layer and the outer hard layer, thereby forming a wrinkled surface. This flexible strategy allows simultaneous construction of complex topologies from 1D to 3D wits well-organized microstructure and controllable dimensions. The mechanism of the influence of ion treating time and pre-stretching ratio on wrinkle wavelength was explored in detail. The finite element simulations matched well with the experimental results. Due to the unique surface and dual crosslinking network, the self-wrinkled hydrogel maintains a high sensitivity of up to 67.47 kPa−1 in 1000 compression cycles. As a high-sensitivity pressure sensor integrated into the detection system, it can be efficiently applied to the contact dynamic tactile perception and monitoring of various movement behaviors of the human body.

A strong, hydrostable lignocellulose-based film based on dual cross-linking networks

Green and sustainable biomass materials based on wood processing residues show considerable application potential as substitutes to petroleum-based plastics. However, due to the chemical and structural characteristics of cellulose fibers resulting in their natural hydrophilicity, it is difficult for a single cross-linking network to impart multiple excellent properties to bio-based materials. Here, with wood lignification enhancement inspiration, a high-performance bio-based plastics based on 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized lignocellulose (TOLC) is successfully fabricated by a dual-crosslinking strategy of sodium lignosulfonate (LS) and epichlorohydrin (ECH) modification, and their characterizations were done in terms of SEM, FTIR, XPS, XRD, TG, contact angle and tensile properties. The physical sacrificial bonding between TOLC and LS, in conjunction with the covalent cross-linking network among the TOLC-LS matrix and ECH, contributed to the exceptional tensile strength (383.43 ± 1.57 MPa) and elastic modulus (15.20 ± 0.66 GPa) of the prepared TOLC-LS/ECH film. Furthermore, the maximum weight loss peak of TOLC-LS/ECH III film is observed at 348 °C, higher than TOLC film, which shows exceptional thermal stability. After immersing in water for 24 h, the water absorption rate of TOLC-LS/ECH III film is only 59.72 % of TOLC film, exhibiting increased water resistance. Remarkably, the resulted bio-mass plastics show superior biodegradability with a weight loss of 33.67 % after 30 days in outdoor conditions, while the tensile strength remained 81 % of the original after 6 months in appropriate indoor environments, showing excellent mechanical stability. Compared with most sustainable bio-based plastics, the obtained film shows combination of low production cost, high mechanical properties, and glorious thermal stability, which can effectively expand its application potential in mulch, daily packaging, and so on. This strategy will pave the way for developing sustainable bio-based plastics with low cost, high-performance, and outstanding processing.

Highly stretchable, fast self-healing nanocellulose hydrogel combining borate ester bonds and acylhydrazone bonds

Self-healing hydrogels have received considerable attention as a promising material for flexible electronic devices given their mechanical durability and structurally tunable properties. In this study, a highly stretchable self-healing hydrogel with dual cross-linking network was developed via borate ester bonds generated by polyvinyl alcohol and borax, and acylhydrazone bonds formed by aldehyde nanocellulose with adipic acid dihydrazide-modified alginate. Compared with the single network hydrogel composed of polyvinyl alcohol and borax, the introduction of dynamic acylhydrazone bonds greatly increases the flexibility of the hydrogel. The elongation rate increased from 480 % to approximately 1440 %, and the self-healing efficiency increased from 84.6 % to 92.7 % after healing for 60 min at ambient temperature without any stimulus. Moreover, the longer the self-healing time, the more evident the self-healing effect of the acylhydrazone bonds. In addition, electrical measurements confirmed a wide working strain range (ca.1000 %), durability, and reliability. Once assembled as a strain sensor, the hydrogel is able to monitor both large and subtle human motions. Besides, this hydrogel exhibited desirable biocompatibility, as demonstrated by in vitro cytotoxicity towards NIH 3T3 cells. These integrated properties make this nanocomposite hydrogel a promising candidate for future applications as green, flexible, and smart sensors.