A Biodegradable, Waterproof, and Thermally Processable Cellulosic Bioplastic Enabled by Dynamic Covalent Modification

A new 3D printing strategy by enhancing shear-induced alignment of gelled nanomaterial inks resulting in stronger and ductile cellulose films

Cellulose nanofibrils (CNFs) are derived from biomass and have significant potential as fossil-based plastic alternatives used in disposable electronics. Controlling the nanostructure of fibrils is the key to obtaining strong mechanical properties and high optical transparency. Vacuum filtration is usually used to prepare the CNFs film in the literature; however, such a process cannot control the structure of the CNFs film, which limits the transparency and mechanical strength of the film. Here, direct ink writing (DIW), a pressure-controlled extrusion process, is proposed to fabricate the CNFs film, which can significantly harness the alignment of fibrils by exerting shear stress force on the filaments. The printed films by DIW have a compact structure, and the degree of fibril alignment quantified by the small angle X-ray diffraction (SAXS) increases by 24 % compared to the vacuum filtration process. Such a process favors the establishment of the chemical bond (or interaction) between molecules, therefore leading to considerably high tensile strength (245 ± 8 MPa), elongation at break (2.2 ± 0.5 %), and good transparency. Thus, proposed DIW provides a new strategy for fabricating aligned CNFs films in a controlled manner with tunable macroscale properties. Moreover, this work provides theoretical guidance for employing CNFs as structural and reinforcing materials to design disposable electronics.

Multi-Modal Melt-Processing of Birefringent Cellulosic Materials for Eco-Friendly Anti-Counterfeiting

Ubiquitous anti-counterfeiting materials with a rapidly rising annual consumption (over 1010 m2) can pose a serious environmental burden. Biobased cellulosic materials with birefringence offer attractive sustainable alternatives, but their scalable solvent-free processing remain challenging. Here, a dynamic chemical modification strategy is proposed for multi-modal melt-processing of birefringent cellulosic materials for eco-friendly anti-counterfeiting. Relying on the thermal-activated dynamic covalent-locking of the spatial topological structure of preferred oriented cellulose, the strategy balances the contradiction between the strong confinement of long-range ordered structures and the molecular motility required for entropically-driven reconstruction. Equipped with customizable processing forms including mold-pressing, spinning, direct-ink-writing, and blade-coating, the materials exhibit a wide color gamut, self-healing efficiency (94.5%), recyclability, and biodegradability. Moreover, the diversified flexible elements facilitate scalable fabrication and compatibility with universal processing techniques, thereby enabling versatile and programmable anti-counterfeiting. The strategy is expected to provide references for multi-modal melt-processing of cellulose and promote sustainable innovation in the anti-counterfeiting industry.

Emerging approaches of utilizing trees to produce advanced structural and functional materials

The global number of trees is approximately 3 trillion, covering 31% of the land area. Trees are considered a cheap, abundant, renewable, and environmentally friendly feedstock for producing advanced structural and functional materials toward a widespread application in sustainable energy and environment. In this highlight, we reveal the structure and composition of wood, leaves, and tree extracts, and then highlight the strategies to control their hierarchical structures and properties. Moreover, we provide an up-to-date overview of their emerging applications in sustainable buildings, ionic nanofluidics, batteries, capacitors, solar cells, environmental remediation, biodegradable packaging, and nanomaterial synthesis. Finally, we outline the challenges and opportunities in valorizing trees for creating a sustainable future.

Flexible vanillin-polyacrylate/chitosan/mesoporous nanosilica-MXene composite film with self-healing ability towards dual-mode sensors

Manufacturing flexible sensors with prominent mechanical properties, multifunctional sensing abilities, and remarkable self-healing capabilities remains a difficult task. In this study, a novel vanillin-modified polyacrylate (VPA), which is capable of forming green dynamic covalent crosslinking with chitosan (CS), was synthesized. The synthesized VPA was combined with mesoporous silica-modified MXene (AMS-MXene) and covalently cross-linked simultaneously with CS, resulting in the formation of a flexible composite conductive film designed for dual-mode sensors. Due to the multidimensional structure formed by the mesoporous silica and MXene layers, the resulting composite film is not only suitable for strain sensing but also excels in gas response sensing. Most importantly, the composite films demonstrate a remarkable self-healing capability through reversible dynamic covalent bonds, specifically Schiff base bonds, coupled with multiple hydrogen bonding interactions with AMS-MXene. This robust self-repair functionality remains effective even at a low temperature of 30 °C. Additionally, the synergistic antibacterial effect exerted by vanillin and CS in the film can endow the composite sensor with excellent antimicrobial properties. This multifunctional composite film holds tremendous potential for applications in green flexible wearable sensors. Furthermore, it can show diverse applications in a wide variety of fields, driving advances in wearable technology and human health monitoring.

New Advances in Covalent Network Polymers via Dynamic Covalent Chemistry

Covalent network polymers, as materials composed of atoms interconnected by covalent bonds in a continuous network, are known for their thermal and chemical stability. Over the past two decades, these materials have undergone significant transformations, gaining properties such as malleability, environmental responsiveness, recyclability, crystallinity, and customizable porosity, enabled by the development and integration of dynamic covalent chemistry (DCvC). In this review, we explore the innovative realm of covalent network polymers by focusing on the recent advances achieved through the application of DCvC. We start by examining the history and fundamental principles of DCvC, detailing its inception and core concepts and noting its key role in reversible covalent bond formation. Then the reprocessability of covalent network polymers enabled by DCvC is thoroughly discussed, starting from the significant milestones that marked the evolution of these polymers and progressing to their current trends and applications. The influence of DCvC on the crystallinity of covalent network polymers is then reviewed, covering their bond diversity, synthesis techniques, and functionalities. In the concluding section, we address the current challenges faced in the field of covalent network polymers and speculates on potential future directions.

Electrospun membranes of diselenide-containing poly(ester urethane)urea for in situ catalytic generation of nitric oxide

Nitric oxide (NO) plays an important role as a signalling molecule in the biological system. Organoselenium-coated or grafted biomaterials have the potential to achieve controlled NO release as they can catalyse decomposition of endogenous S-nitrosothiols to NO. However, such biomaterials are often challenged by the loss of the catalytic sites, which can affect the stability in tissue repair applications. In this work, we prepare a diselenide-containing poly(ester urethane)urea (SePEUU) polymer with Se-Se in the backbone, which is further electrospun into fibrous membranes by blending with poly(ester urethane)urea (PEUU) without diselenide bonds. The presence of catalytic sites in the main chain demonstrates stable and long-lasting NO catalytic activity, while the porous structure of the fibrous membranes ensures uniform distribution of the catalytic sites and better contact with the donor-containing solution. PEUU/SePEUU50 in 50/50 mass ratio has a physiologically adapted rate of NO release, with a sustained generation of NO after exposure to PBS at 37 °C for 30 d. PEUU/SePEUU50 has a low hemolysis and protein adsorption, with mechanical properties in the wet state matching those of natural vascular tissues. It can promote the adhesion and proliferation of human umbilical vein endothelial cells in vitro and control the proliferation of vascular smooth muscle cells in the presence of NO generation. This study exhibits the electrospun fibrous membranes have potential for utilizing as hemocompatible biomaterials for regeneration of blood-contacting tissues.

Fabrication of fully bio-based malleable thermoset derived from cellulose, furfural and plant oil for advanced capacitive sensor

Fabrication of sustainable bio-based malleable thermosets (BMTs) with excellent mechanical properties and reprocessing ability for applications in electronic devices has attracted more and more attention but remains significant challenges. Herein, the BMTs with excellent mechanical robustness and reprocessing ability were fabricated via integrating with radical polymerization and Schiff-base chemistry, and employed as the flexible substrate to prepare the capacitive sensor. To prepare the BMTs, an elastic bio-copolymer derived from plant oil and 5-hydroxymethylfurfural was first synthesized, and then used to fabricate the dynamic crosslinked BMTs through Schiff-base chemistry with the amino-modified cellulose and polyether amine. The synergistic effect of rigid cellulose backbone and the construction of dynamic covalent crosslinking network not only achieved high tensile strength (8.61 MPa) and toughness (3.77 MJ/m3) but also endowed the BMTs with excellent reprocessing ability with high mechanical toughness recovery efficiency of 104.8 %. More importantly, the BMTs were used as substrates to fabricate the capacitive sensor through the CO2-laser irradiation technique. The resultant capacitive sensor displayed excellent and sensitive humidity sensing performance, which allowed it to be successfully applied in human health monitoring. This work paved a promising way for the preparation of mechanical robustness malleable bio-thermosets for electronic devices.

Eco-friendly cellulose-based antioxidation film by partial esterification

Cellulose nanocrystals (CNCs) have received increasing attention because of their superior dispersion and thermal stability. In this study, TEMPO-oxidized cellulose nanocrystal (TOCNC) multifunctional antioxidationantioxidation films (TOCNC-GA film) were prepared by the esterification of TOCNC and gallic acid (GA). TOCNC-GAX films, where X represents the ratio of the amount of GA to the amount of TOCNC, were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The films with the GA:TOCNC ratio of 1:1 achieved higher interfacial compatibility than the other films. The mechanical properties and water resistance of the TOCNC-GA films were superior than those of pure TOCNC films. Moreover, the original TOCNC structure changed owing to the presence of GA, which endowed a certain thermoplasticity owing to the formation of ester groups. The antioxidation properties of the TOCNC-GA1 films reached 43.8 % and 71.85 % after 6 and 24 h, respectively, as evaluated by the 2,2-biphenyl-1-picrylhydrazyl method and the free radical scavenging activities of the TOCNC-GA1 films. The innovative development of the functional antioxidation film presented in this paper has great potential for use in antioxidation packaging materials and food preservation.

Insights into the enhanced mechanism of electron beam pretreatment on application performance for poly (butylene adipate-co-terephthalate)/acetylated cellulose composite plastics

In this work, we developed a strategy to construct poly (butylene adipate-co-terephthalate) (PBAT) composite plastics with excellent mechanical properties, superior thermal stability and enhanced biodegradability by combining acetylated celluloses (ECs) mediated by electron beam irradiation (EBI), which works as a toughening agent. With findings, the EBI pretreatment assisted with acetylation was applied to develop ECs materials with a higher degree of acetylation than acetylation alone. The pretreated ECs with increased hydrophobicity tended to decrease the chance of self-aggregation and enhanced the interfacial compatibility and adhesion with PBAT in PBAT/ECs composite plastics. Thus, PBAT/ECs composite plastics exhibited a smoother and more uniform surface structure during preparation and offered higher tensile strength, water vapor transmission rate, water absorption rate, thermal stability and degradation rate, and lower elongation at a break during application. On top of that, the PBAT/ECs composite plastics were characterized by a series of methods containing Fourier transform infrared spectroscopy and X-ray diffraction, indicating that these properties are mainly caused by the acetylation of hydroxyl groups from cellulose and carboxyl groups of PBAT. The work is expected to expand the application scope of PBAT and cellulose and provide an attainable solution for a biodegradable substitute for traditional plastics.

Desirable Strong and Tough Adhesive Inspired by Dragonfly Wings and Plant Cell Walls

The production of wood-based panels has a significant demand for mechanically strong and flexible biomass adhesives, serving as alternatives to nonrenewable and toxic formaldehyde-based adhesives. Nonetheless, plywood usually exhibits brittle fracture due to the inherent trade-off between rigidity and toughness, and it is susceptible to damage and deformation defects in production applications. Herein, inspired by the microstructure of dragonfly wings and the cross-linking structure of plant cell walls, a soybean meal (SM) adhesive with great strength and toughness was developed. The strategy was combined with a multiple assembly system based on the tannic acid (TA) stripping/modification of molybdenum disulfide (MoS2@TA) hybrids, phenylboronic acid/quaternary ammonium doubly functionalized chitosan (QCP), and SM. Motivated by the microstructure of dragonfly wings, MoS2@TA was tightly bonded with the SM framework through Schiff base and strong hydrogen bonding to dissipate stress energy through crack deflection, bridging, and immobilization. QCP imitated borate chemistry in plant cell walls to optimize interfacial interactions within the adhesive by borate ester bonds, boron-nitrogen coordination bonds, and electrostatic interactions and dissipate energy through sacrificial bonding. The shear strength and fracture toughness of the SM/QCP/MoS2@TA adhesive were 1.58 MPa and 0.87 J, respectively, which were 409.7% and 866.7% higher than those of the pure SM adhesive. In addition, MoS2@TA and QCP gave the adhesive good mildew resistance, durability, weatherability, and fire resistance. This bioinspired design strategy offers a viable and sustainable approach for creating multifunctional strong and tough biobased materials.

Silver nanoparticles coated cellulose-based flexible membrane with excellent UV resistance, high infrared reflection and water resistance for personal thermal management

Designing of a green and multifunctionally integrated cellulose-based flexible wearable material with personal thermoregulation, water and ultraviolet (UV) resistance is essential for the development of personal thermal management and smart textiles. Herein, a hydrophobic silver nanoparticles cellulose-based membrane (H-AgNPs/CEPCM) was prepared through simple solution blending, spin-coating process and chemical vapor modification. The prepared membrane exhibited excellent UV resistance due to the synergistic effect of carbon quantum dots (CQDs) as well as UV-absorbing functional groups. The spin-coated AgNPs layer with high infrared reflectivity has great radiant insulation, and temperature was reduced by 3.4 °C compared with H-CEPCM in indoor environment. Furthermore, the mechanical properties of H-AgNPs/CEPCM were significantly improved by the introduction of amide and ether bonds, as well as a large number of hydrogen bonds. This led to a tensile strength of 23.21 MPa and an elongation at break of 16.57 %, while also providing water resistance. Additionally, the H-AgNPs/CEPCM exhibited outstanding thermal stability and hydrophobicity. This work may provide a feasible and promising strategy for the construction of multifunctional integrated cellulose membrane materials for radiant insulation, outdoor textiles and novel UV protection applications.

A Tough Monolithic-Integrated Triboelectric Bioplastic Enabled by Dynamic Covalent Chemistry

Electronic waste is a growing threat to the global environment and human health, raising particular concerns. Triboelectric devices synthesized from sustainable and degradable materials are a promising electronic alternative, but the mechanical mismatch at the interface between the polymer substrate and the electrodes remains unresolved in practical applications. This study uses the sulfhydryl silanization reaction and the chemical selectivity and site specificity of the thiol-disulfide exchange reaction in dynamic covalent chemistry to prepare a tough monolithic-integrated triboelectric bioplastic. The stress is dissipated by covalent bond adaptation to the interface interaction, which makes the polymer dielectric layer to the conductive layer have a good interface adhesion effect (220.55 kPa). The interfacial interlocking of the polymer substrate with the conductive layer gives the triboelectric bioplastic excellent tensile strength (87.4 MPa) and fracture toughness (33.3 MJ m-3). Even when subjected to a tension force of 10 000 times its weight, it still maintains a stable triboelectric output with no visible cracks. This study provides new insights into the design of reliable and environmentally friendly self-powered devices, which is significant for the development of flexible wearable electronics.

Biodegradable, Strong, and Hydrophobic Regenerated Cellulose Films Enriched with Esterified Lignin Nanoparticles

The scientific community is pursuing significant efforts worldwide to develop environmentally viable film materials from biomass, particularly transparent, high-performance regenerated cellulose (RC) films, to replace traditional plastics. However, the inferior mechanical performance and hydrophilic nature of RC films are generally not suitable for use as a substitute for plastics in practical applications. Herein, lignin homogenization is used to synthesize high-performance composite films. The esterified lignin nanoparticles (ELNPs) with dispersible and binding advantages are prepared through esterification and nanometrization. In the presence of ELNPs, RC films exhibit a higher tensile strength (110.4 MPa), hydrophobic nature (103.6° water contact angle, 36.6% water absorption at 120 min, and 1.127 × 10-12 g cm cm-2 s-1 Pa-1 water vapor permeability), and exciting optical properties (high visible and low ultraviolet transmittance). The films further display antioxidant activity, oxygen barrier ability, and thermostability. The films completely biodegrade at 12 and 30% soil moisture. Overall, this study offers new insights into lignin valorization and regenerated cellulose composite films as novel bioplastic materials.

Chitinous Bioplastic Enabled by Noncovalent Assembly

Natural polymeric-based bioplastics usually lack good mechanical or processing performance. It is still challenging to achieve simultaneous improvement for these two usual trade-off features. Here, we demonstrate a full noncovalent mediated self-assembly design for simultaneously improving the chitinous bioplastic processing and mechanical properties via plane hot-pressing. Tannic acid (TA) is chosen as the noncovalent mediator to (i) increase the noncovalent cross-link intensity for obtaining the tough noncovalent network and (ii) afford the dynamic noncovalent cross-links to enable the mobility of chitin molecular chains for benefiting chitinous bioplastic nanostructure rearrangement during the shaping procedure. The multiple noncovalent mediated network (chitin-TA and chitin-chitin cross-links) and the pressure-induced orientation nanofibers structure endow the chitinous bioplastics with robust mechanical properties. The relatively weak chitin-TA noncovalent interactions serve as water mediation switches to enhance the molecular mobility for endowing the chitin/TA bioplastic with hydroplastic processing properties, rendering them readily programmable into versatile 2D/3D shapes. Moreover, the fully natural resourced chitinous bioplastic exhibits superior weld, solvent resistance, and biodegradability, enabling the potential for diverse applications. The full physical cross-linking mechanism highlights an effective design concept for balancing the trade-off of the mechanical properties and processability for the polymeric materials.

Enhancing Cross-Linking Network for Superior Wet Strength of Paper by Sustainable Hyperbranched Polyimines

The paper industry has long been a crucial part of our lives, providing printing materials, tissue paper, and packaging products. However, the low wet strength of commercially available paper limits its application in packaging, particularly when it comes into contact with liquids. To address this issue, researchers have explored various strategies, including the use of wet strength agents. The most widely used agent, polyamide-epichlorohydrin resin (PAE), has limitations, such as poor dimensional stability and limited recyclability. Additionally, PAE can release harmful chlorinated organics. To overcome these challenges, we report a novel approach using a hyperbranched wet strength agent (referred to as "OA-PI") based on the cross-linking of oxidized amylopectin from waxy corn and polyamines through the Schiff base reaction. The hyperbranched structure of OA-PI provides multiple binding sites, enhancing the cross-linking strength of cellulosic paper under wet conditions. The paper treated with OA-PI exhibited exceptional wet strength, significantly higher than that of PAE-treated paper and paper with traditional starch-based additives. Moreover, the biomass-based OA-PI showed improved recyclability and reduced harm from chlorinated organic compounds. This study not only enhances the wet strength of paper but also opens sustainable avenues for the design of functional adhesives.

Insight into the Feasibility of Fatty Acyl Chlorides with 10-18 Carbons for the Ball-Milling Synthesis of Thermoplastic Cellulose Esters

Fatty acid cellulose esters (FACE) are common cellulose-based thermoplastics, and their thermoplasticity is determined by both the contents and the lengths of the side chains. Herein, various FACE were synthesized by the ball-milling esterification of cellulose and fatty acyl chlorides containing 10-18 carbons, and their structures and thermoplasticity were thoroughly studied. The results showed that FACE with high degrees of substitution (DS) and low melting flow temperatures (Tf) were achieved as the chain lengths of the fatty acyl chlorides were reduced. In particular, a cellulose decanoate with a DS of 1.85 and a Tf of 186 °C was achieved by feeding 3 mol of decanoyl chloride per mole anhydroglucose units of cellulose. However, cellulose stearate (DS = 1.53) synthesized by the same protocols cannot melt even at 250 °C. More interestingly, the fatty acyl chlorides with 10 and 12 carbons resulted in FACE with superior toughness (elongation at break up to 94.4%). In contrast, due to their potential crystallization of the fatty acyl groups with 14-18 carbons, the corresponding FACE showed higher tensile strength and Young's modulus than the others. This study provides some theoretical basis for the mechanochemical synthesis of thermoplastic FACE with designated properties.

All-natural chitosan-based polyimine vitrimer with multiple advantages: A novel strategy to solve nondegradable plastic waste pollution

The increasing amount of nondegradable petroleum-based plastic waste releases chemical hazards, posing a significant threat to the environment and human health. Chitosan, derived from marine wastes, is an attractive feedstock for the preparation of plastic replacement due to its renewable and degradable nature. However, in most cases, complex chemical modifications of chitosan or hybridization with chemicals from fossil resources are required. Herein, we present a high-performance chitosan-based polyimine vitrimer (CS-PI) through a mild and catalyst-free Schiff base reaction between chitosan and vanillin. The CS-PI were formed by integrating dynamic imine bonds into the polymer networks, resulting in superior thermo-processability and mechanical performances. The tensile strength and Young's modulus of the CS-PI films reached 38.72 MPa and 3.20 GPa, respectively, which was significantly higher than that of both commercial petroleum-based plastics and bioplastics. Additionally, the CS-PI films exhibited good light transmittance, self-healing ability, reprocess capacity, water resistance, and durability to various organic solvents. Moreover, the CS-PI films could be completely degraded under both acidic and natural conditions, enabling a sustainable circulation. Therefore, this work offers a new design strategy for developing all-natural environmentally friendly polymers as sustainable replacements for petroleum-based plastics, thus reducing the accumulation of nondegradable plastic waste.

A supramolecular approach for converting renewable biomass into functional materials

The rational transformation and utilization of biomass have attracted increasing attention because of its high importance in sustainable development and green economy. In this study, we used a supramolecular approach to convert biomass into functional materials. Six biomass raw materials with distinct chemical structures and physical properties were copolymerized with thioctic acid (TA) to afford poly[TA-biomass]s. The solvent-free copolymerization leads to the convenient and quantitative fabrication of biomass-based versatile materials. The non-covalent bonding and reversible solid-liquid transitions in poly[TA-biomass]s endow them with diversified features, including thermal processability, 3D printing, wet and dry adhesion, recyclability, impact resistance, and antimicrobial activity. Benefiting from their good biocompatibility and nontoxicity, these biomass-based materials are promising candidates for biological applications.

Lobster-Inspired Chitosan-Derived Adhesives with a Biomimetic Design

Polysaccharide-based adhesives, especially chitosan (CS)-derived adhesives, serve as promising sustainable alternatives to traditional adhesives. However, most demonstrate a poor adhesive strength. Inspired by the inherent layered structure of marine arthropods (lobsters), a core-shell structure (SiO2-NH2@OPG) with amine-functionalized silica (SiO2-NH2) as the core and oxidized pyrogallol (OPG) as the shell is prepared in this study. The compound is blended with CS to produce a structural biomimetic wood adhesive (SiO2-NH2@OPG/CS) with excellent performance. In addition to thermocompressive curing, this adhesive exhibits a water-evaporation-induced curing behavior at room temperature. With reference to the design mechanism of the lobster cuticle, this microphase-separated structure consists of clustered nanofibers with varying amounts of SiO2-NH2@OPG particles between the fibers. This intriguing microphase structure and its mechanical effects could offer a powerful solution for improving the functional modification of wood composites.

Green, recyclable, mechanically robust, wet-adhesive and ionically conductive cellulose-based bioplastics enabled by supramolecular covalent hydrophobic eutectic networks

The development of novel cellulose-based bioplastics (CBPs) is highly desirable because CBPs are green, rationally use resources, and lead to a reduction in environmental pollution compared to alternative materials. However, incorporating high transparency, water resistance, mechanical robustness, wet-adhesion, ionic conductivity and recyclability into CBP remains a challenge. In this paper, novel CBPs with supramolecular covalent networks are fabricated by introducing polymerizable hydrophobic deep eutectic solvents (HDES) into ethylcellulose (EC) networks through in situ plasticization followed by a rapid photopolymerization process. The excellent molecular interfacial compatibility enables EC to be loaded with a high content of poly(HDES), while allowing high transparency (more than 90 %) of the prepared CBPs. Multiple intermolecular interactions provide CBPs with mechanical robustness, water resistance, and underwater adhesion, and CBPs can be readily recovered by the solvent in a closed loop. Moreover, CBPs possess inherent ionic conductivities, and using them as green substrates, personalized electroluminescent devices can be successfully constructed. The method proposed in this paper provides a new strategy for the preparation of multifunctional CBPs, which will greatly enrich their applications in self-adhesive materials, green flexible electronics and other package materials.

High Toughness, Multi-dynamic Self-Healing Polyurethane for Outstanding Energy Harvesting and Sensing

Triboelectric nanogenerators (TENGs) are an emerging class of energy harvesting devices with considerable potential across diverse applications, including wearable electronic devices and self-powered sensors. However, sustained contact, friction, and incidental scratches during operation can lead to a deterioration in the electrical output performance of the TENG, thereby reducing its overall service life. To address this issue, we developed a self-healing elastomer by incorporating disulfide bonds and metal coordination bonds into the polyurethane (PU) chain. The resulting elastomer demonstrated exceptional toughness, with a high value of 85 kJ m-3 and an impressive self-healing efficiency of 85.5%. Specifically, the TENG based on that self-healing PU elastomer generated a short circuit current of 12 μA, an open circuit voltage of 120 V, and a transfer charge of 38.5 nC within a 2 cm × 2 cm area, operating in contact-separation mode. With an external resistance of 20 MΩ, the TENG achieved a power density of 2.1 W m-2. Notably, even after self-healing, the electrical output performance of the TENG was maintained at 95% of the undamaged device. Finally, the self-healing TENG was employed to construct a self-powered noncontact sensing system that can be applied to monitor human motion accurately. This research may expand the application prospects of PU materials in future human-computer interaction and self-powered sensing fields.

Biodegradable Dual-Network Cellulosic Composite Bioplastic Metafilm for Plastic Substitute

With the escalating environmental and health concerns over petroleum-based plastics, sustainable and biodegradable cellulosic materials are a promising alternative to plastics, yet remain unsatisfied properties such as fragility, inflammability and water sensitivity for practical usage. Herein, we present a novel dual-network design strategy to address these limitations and fabricate a high-performance cellulosic composite bioplastic metafilm with the exceptional mechanical toughness (23.5 MJ m-3 ), flame retardance, and solvent resistance by in situ growth of cyclotriphosphazene-bridged organosilica network within bacterial cellulose matrix. The phosphorus, nitrogen-containing organosilica network, verified by the experimental and theoretical results, plays a triple action on significantly enhancing tensile strength, toughness, flame retardance and water resistance of composite bioplastic metafilm. Furthermore, cellulosic bioplastic composite metafilm demonstrates a higher maximum usage temperature (245 °C), lower thermal expansion coefficient (15.19 ppm °C-1 ), and better solvent resistance than traditional plastics, good biocompatibility and natural biodegradation. Moreover, the composite bioplastic metafilm have a good transparency of average 74 % and a high haze over 80 %, which can serve as an outstanding substrate substitute for commercial polyethylene terephthalate film to address the demand of flexible ITO films. This work paves a creative way to design and manufacture the competitive bioplastic composite to replace daily-used plastics.

Reconstruction of Cellulose Intermolecular Interactions from Hydrogen Bonds to Dynamic Covalent Networks Enables a Thermo-processable Cellulosic Plastic with Tunable Strength and Toughness

Its excellent renewability and biodegradability make cellulose an attractive resource to prepare fossil-based plastic alternatives. However, cellulose itself exhibits strong intermolecular hydrogen bond (H-bond) interactions, significantly restricting the mobility of cellulose chains, thus leading to poor thermo-processing performance. Here, we reconstructed the intermolecular interactions of cellulose chains via replacing the original H-bonds with dynamic covalent bonds. By this, cellulose can be easily thermo-processed into a cellulosic plastic under mild conditions (70 °C). Through adjusting the chemical structure of dynamic covalent networks, the cellulosic plastic shows tunable mechanical strength (3.0-33.5 MPa) and toughness (43-321 kJ m-2). The cellulosic plastic also exhibits excellent resistance to water, organic solvent, acid solution, alkali solution, and high temperature (>400 °C). Moreover, it owns good chemical and biological degradability and recyclability. This work provides an effective method to develop high-performance cellulosic plastics for fossil-based plastic substitution.

Lignocellulose-Based Optical Biofilter with High Near-Infrared Transmittance via Lignin Capturing-Fusing Approach

Near-infrared (NIR) transparent optical filters show great promise in night vision and receiving windows. However, NIR optical filters are generally prepared by laborious, environmentally unfriendly processes that involve metal oxides or petroleum-based polymers. We propose a lignin capturing-fusing approach to manufacturing optical biofilters based on molecular collaboration between lignin and cellulose from waste agricultural biomass. In this process, lignin is captured via self-assembly in a cellulose network; then, the lignin is fused to fill gaps and hold the cellulose fibers tightly. The resulting optical biofilter featured a dense structure and smooth surface with NIR transmittance of ~90%, ultralow haze of close to 0%, strong ultraviolet-visible light blocking (~100% at 400 nm and 57.58% to 98.59% at 550 nm). Further, the optical biofilter has comprehensive stability, including water stability, solvent stability, thermal stability, and environmental stability. Because of its unique properties, the optical biofilter demonstrates potential applications in the NIR region, such as an NIR-transmitting window, NIR night vision, and privacy protection. These applications represent a promising route to produce NIR transparent optical filters starting from lignocellulose biomass waste.

Protein fibers with self-recoverable mechanical properties via dynamic imine chemistry

The manipulation of internal interactions at the molecular level within biological fibers is of particular importance but challenging, severely limiting their tunability in macroscopic performances and applications. It thus becomes imperative to explore new approaches to enhance biological fibers' stability and environmental tolerance and to impart them with diverse functionalities, such as mechanical recoverability and stimulus-triggered responses. Herein, we develop a dynamic imine fiber chemistry (DIFC) approach to engineer molecular interactions to fabricate strong and tough protein fibers with recoverability and actuating behaviors. The resulting DIF fibers exhibit extraordinary mechanical performances, outperforming many recombinant silks and synthetic polymer fibers. Remarkably, impaired DIF fibers caused by fatigue or strong acid treatment are quickly recovered in water directed by the DIFC strategy. Reproducible mechanical performance is thus observed. The DIF fibers also exhibit exotic mechanical stability at extreme temperatures (e.g., -196 °C and 150 °C). When triggered by humidity, the DIFC endows the protein fibers with diverse actuation behaviors, such as self-folding, self-stretching, and self-contracting. Therefore, the established DIFC represents an alternative strategy to strengthen biological fibers and may pave the way for their high-tech applications.