Scalable Fabrication of Structurally Stable Polymer Film with Excellent UV-Shielding, Fluorescent, and Antibacterial Capabilities.

This research presents a new approach to facilely fabricating a multifunctional film using polyvinyl alcohol (PVA) as the base material. The film is modified chemically to incorporate various desirable properties such as high transparency, UV-shielding, antibacterial activity, and fluorescence. The fabrication process of this film is straightforward and efficient. The modified film showed exceptional UV-blocking capability, effectively blocking 100% of UV radiation. It also exhibits strong antibacterial properties. Additionally, the film emitted bright blue fluorescence, which can be useful in various optical and sensing applications. Despite the chemical modification, the film retained the excellent properties of PVA, including high transparency (90%) at 550 nm and good mechanical strength. Furthermore, it demonstrated remarkable stability even under harsh conditions such as exposure to long-term UV radiation, extreme temperatures (-40 or 120 °C), or immersion in different solvents. Overall, this work showcases a promising strategy to develop versatile, structurally stable, transparent, and flexible polymer films with multiple functionalities. These films have potential applications in various fields that require protection, such as packaging materials, biomedical devices, and optical components.

Tough, Highly Oriented, Super Thermal Insulating Regenerated All-Cellulose Sponge-Aerogel Fibers Integrating a Graded Aligned Nanostructure.

Thermal insulating fibers can effectively regulate the human body temperature and decrease indoor energy consumption. However, designing super thermal insulating fibers integrating a sponge and aerogel structure based on biomass resources is still a challenge. Herein, a flow-assisted dynamic dual-cross-linking strategy is developed to realize the steady fabrication of regenerated all-cellulose graded sponge-aerogel fibers (CGFs) in a microfluidic chip. The chemically cross-linked cellulose solution is used as the core flow, which is passed through two sheath flow channels, containing either a diffusion solvent or a physical cross-linking solvent, resulting in CGFs with a porous sponge outer layer and a dense aerogel inner layer. By regulating and simulating the flow process in the microfluidic chip, CGFs with adjustable sponge thicknesses, excellent toughness (26.20 MJ m-3), and ultralow thermal conductivity (0.023 W m-1 K-1) are fabricated. This work provides a new method for fabricating graded biomass fibers and inspires attractive applications for thermal insulation in textiles.

Lithium Bonds Enable Small Biomass Molecule-Based Ionoelastomers with Multiple Functions for Soft Intelligent Electronics.

Lipoic acid (LA), which originates from animals and plants, is a small biomass molecule and has recently shown great application value in soft conductors. However, the severe depolymerization of LA places a significant limitation on its utilization. A strategy of using Li-bonds as both depolymerization quenchers and dynamic mediators to melt transform LA into high-performance ionoelastomers (IEs) is proposed. They feature dry networks while simultaneously combining transparency, stretchability, conductivity, self-healing ability, non-corrosive property, re-mouldability, strain-sensitivity, recyclability, and degradability. Most of the existing soft conductors' drawbacks, such as the tedious synthesis, non-renewable polymer networks, limited functions, and single-use only, are successfully solved. In addition, the multi-functions allow IEs to be used as soft sensors in human-computer interactive games and wireless remote sports assistants. Notably, the recycled IE also provides an efficient conductive filler for transparent ionic papers, which can be used to design soft transparent triboelectric nanogenerators for energy harvesting and multidirectional motion sensing. This work creates a new direction for future research involving intelligent soft electronics.

Transparent Cellulose-Based Film with High UV-Blocking Performance Fabricated by Surface Modification using Biginelli Reaction.

Efficient and sustainable ultraviolet (UV)-blocking materials are of great interest in many fields. Herein, novel cellulose-based UV-blocking films are developed via surface modification using the Biginelli reaction. The resulting films exhibited excellent visible transparency (80%) at 550 nm and superhigh UV-blocking performance, which can shield almost 100% UVA and UVB. These features are very stable even the materials are being subjected to solvents, UV irradiation, and thermal treatment. This work provides a novel and facile strategy to fabricate functional cellulose-based films with superhigh anti-ultraviolet performance.

Freely Moldable Modified Starch as a Sustainable and Recyclable Plastic.

Efficiently preparing a starch-based plastic with moisture insensitivity and toughness is a challenge to improve the high-value utilization of polysaccharide resources. Herein, a sustainable, recyclable starch-based plastic was prepared in a facile and eco-friendly way. First, starch acetoacetate (SAA) with different degrees of substitution (DSs) was synthesized by transesterification. Then, the SAA film was obtained through a solvent-free hot-pressing method. Notably, SAA with different DSs exhibited various glass transition temperatures (109-140 °C), and SAA with high DS (>0.84) was insoluble even after boiling in water for 1 h. Also, the maximum fracture strength of SAA film up to 15.5 MPa and a maximum elongation at break up to 30% were reached . In addition, the starch-based plastic film retained the original mechanical properties after three cycles of hot processing. In consideration of the facile preparation process, this protocol provided a new avenue for developing sustainable and recyclable starch-based plastics.

Starch Formates: Synthesis and Modification.

Starch can be efficiently converted into the corresponding formates homogeneously using N-formyl imidazole obtained by the reaction of 1,1'-carbonyldiimidazole and formic acid in dimethyl sulfoxide as a solvent. Starch formates are soluble in polar aprotic solvents, not susceptible against hydrolysis, and not meltable. Thermoplastics could be generated by conversion of starch formates with long-chain fatty acids exemplified by the conversion with lauroyl chloride in N,N-dimethylacetamide, leading to mixed starch laurate formates. The mixed esters show melting temperatures mainly dependent on the amount of laurate ester moieties.

Highly Stretchable and Compressible Cellulose Ionic Hydrogels for Flexible Strain Sensors.

Stretchable and compressible hydrogels based on natural polymers have received immense considerations for electronics. The feasibility of using pure natural polymer-based hydrogels could be improved if their mechanical behaviors satisfy the requirements of practical applications. Herein, we report highly stretchable (tensile strain ∼126%) and compressible (compression strain ∼80%) cellulose ionic hydrogels (CIHs) among pure natural polymer-based hydrogels including cellulose, chitin, and chitosan via chemical cross-linking based on free radical polymerization of allyl cellulose in NaOH/urea aqueous solution. In addition, the hydrogels have good transparency (transmittance of ∼89% at 550 nm) and ionic conductivity (∼0.16 mS cm-1) and can be worked at -20 °C without freezing and visual loss of transparency. Moreover, the CIHs can serve as reliable and stable strain sensors and have been successfully used to monitor human activities. Significantly, the various properties of hydrogel can be controlled through rationally adjusting the chemically cross-linked density. Our methodology will prove useful in developing the satisfied mechanical and transparent CIHs for a myriad of applications in flexible electronics.

Saccharide branched cellulose with controllable molecular structure and excellent water retention ability.

In this work, saccharide branched cellulose (saccharide b-Cel) was synthesized by combining reducing saccharides with cellulose molecules using Ugi four-component reaction (Ugi-4CR). First, the carboxyl groups required for Ugi-4CR are obtained by carboxymethylating cellulose molecules. Then, saccharide b-Cel with a controlled molecular structure is formed when the terminal aldehyde group of reducing saccharides combines with the carboxyl group and auxiliary functional group. The types of saccharides, the degree of substitution of carboxymethyl groups, and the degree of branching all affect the molecular structure of saccharide b-Cel. Through molecular structural regulation, the relationship between the branching structure and water retention ability of saccharide b-Cel was examined in detail. This work not only provides new insights into the synthesis of cellulose derivatives, but it also provides a template for the synthesis of other biomass derivatives.

Significantly improve film formability of acetylated xylans by structure optimization and solvent screening.

Acetylated xylans have great potential in fabricating functional film and coating materials, which need a good solubility/dispersibility and film formability in an easily evaporable solvent. However, the changes of film formability with degree of substitution by acetyls (DSAc) in different solvent systems for xylans have not been extensively studied, which limit the application of acetylated xylans in film materials. In this study, acetylated xylans with DSAc of 0-2 were prepared and the effects of acetyl groups on solubility/dispersibility, crystallinity and film formability of xylans in water and chloroform solvent systems were investigated. Due to the change of polarity, xylans with DSAc of 0-0.62 are only soluble in water solvents, while xylans with DSAc of 1.13-2 are only soluble in chloroform/ethanol (70/30 v/v) organic solvents. We have found that the film formability of acetylated xylans is highly related to their solubility and crystallization. Film formable xylans all had good solubility in the cast solvents. However, although with good solubility, xylans with DSAc of 0-0.3 and DSAc of 1.76-2 cannot form intact films, which is due to the forming of xylan hydrate crystals and xylan diacetate crystals. With the increase of DSAc, the mechanical property of xylan film increases initially at low DSAc and decreases at high DSAc. This study provides theoretical basis for applying xylans and their derivatives in advanced functional film and coating materials with great biocompatibility and biodegradability.

Retraction of "Fe3O4 Nanoparticles Grown on Cellulose/GO Hydrogels as Advanced Catalytic Materials for the Heterogeneous Fenton-like Reaction".

[This retracts the article DOI: 10.1021/acsomega.9b00170.].

Cellulose-based fluorescent chemosensor with controllable sensitivity for Fe3+ detection.

Polymer-based sensors, particularly those derived from renewable polymers, are gaining attention for their superior properties compared to organic small molecules. However, their complex preparation and poor, uncontrollable sensitivity have hindered further development. Herein, cellulose-based polymer photoluminescence (PL) chemosensors were fabricated using a straightforward and adjustable strategy. Specifically, water-soluble cellulose acetoacetate (CAA) was used as the substance for the in-situ synthesis of 1,4-dihydropyridine (DHPs) fluorescent rings on cellulose chains via a catalyst-free, room-temperature Hantzsch reaction. Benefiting from the synergetic through-space conjugation of DHPs rings and semi-rigid cellulose chains with heteroatoms, the sensors exhibit bright and stable PL properties. Based on this performance, the cellulose-based sensor excels in the specific recognition of Fe3+ in aqueous systems, showing exceptional selectivity, stability, and anti-interference performance due to the synergy between the inner filter effect (IFE) and intramolecular charge transfer (ICT). Theoretical calculations confirm the role of the extended π-conjugated structure at the DHPs-4 position in modulating the sensor sensitivity, achieving a low limit of detection (LOD) of 0.48 µM. Furthermore, the versatility of the Hantzsch reaction shows the potential of this strategy for developing a new generation of biomass-based polymer portable sensors for real-time and on-site detection.

Lysine-mediated surface modification of cellulose nanocrystal films for multi-channel anti-counterfeiting.

Utilizing advanced multiple channels for information encryption offers a powerful strategy to achieve high-capacity and highly secure data protection. Cellulose nanocrystals (CNCs) offer a sustainable resource for developing information protection materials. In this study, we present an approach that is easy to implement and adapt for the covalent attachment of various fluorescence molecules onto the surface of CNCs using the Mannich reaction in aqueous-based medium. Through the use of the Mannich reaction-based surface modification technique, we successfully achieved multi-color fluorescence in the resulting CNCs. The resulting CNC derivatives were thoroughly characterized by two dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D HSQC NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron (XPS) spectroscopy. Notably, the optical properties of CNCs were well maintained after modification, resulting in films exhibiting blue and red structural colors. This enables the engineering of highly programmable and securely encoded anti-counterfeit labels. Moreover, subsequent coating of the modified CNCs with MXene yielded a highly secure encrypted matrix, offering advanced security and encryption capabilities under ultraviolet, visible, and near-infrared wavelengths. This CNC surface-modification enables the development of multimodal security labels with potential applications across various practical scenarios.

Multifunctioning of carboxylic-cellulose nanocrystals on the reinforcement of compressive strength and conductivity for acrylic-based hydrogel.

Simultaneously having competitive compressive properties, fatigue-resistant stability, excellent conductivity and sensitivity has still remained a challenge for acrylic-based conductive hydrogels, which is critical in their use in the sensor areas where pressure is performed. In this work, an integrated strategy was proposed for preparing a conductive hydrogel based on acrylic acid (AA) and sodium alginate (SA) by addition of carboxylic-cellulose nanocrystals (CNC-COOH) followed by metal ion interaction to reinforce its compressive strength and conductivity simultaneously. The CNC-COOH played a multifunctional role in the hydrogel by well-dispersing SA and AA in the hydrogel precursor solution for forming a uniform semi-interpenetrating network, providing more hydrogen bonds with SA and AA, more -COOH for metal ion interactions to form uniform multi-network, and also offering high modulus to the final hydrogel. Accordingly, the as-prepared hydrogels showed simultaneous excellent compressive strength (up to 3.02 MPa at a strain of 70 %) and electrical conductivity (6.25 S m-1), good compressive fatigue-resistant (93.2 % strength retention after 1000 compressive cycles under 50 % strain) and high sensitivity (gauge factor up to 14.75). The hydrogel strain sensor designed in this work is capable of detecting human body movement of pressing, stretching and bending with highly sensitive conductive signals, which endows it great potential for multi-scenario strain sensing applications.

Passerini three-component reaction for the synthesis of saccharide branched cellulose.

In this work, we investigate a multicomponent synthetic method for combining saccharides with cellulose to produce saccharide branched cellulose (b-Cel). First, cellulose is modified conventionally using carboxymethyl to create carboxyl functional groups for multicomponent reactions. The Passerini three-component reaction (Passerini-3CR) is then used to synthesize the saccharide b-Cel, with particular attention paid to the scope of the substrate and reaction process optimization. The structure of saccharide b-Cel is regulated by modifying the carboxyl group of cellulose molecules, the kind of saccharide molecules (including glucose, galactose, lactose, cellobiose, and cellulose), and the degree of branching. The branched structure of saccharide b-Cel greatly influenced its rheological characteristics and solubility. This work presents a practical method for the synthesis of artificial branching polysaccharides and is crucial for the development of innovative materials based on biomass.

High efficiency electro- and photo-thermal conversion cellulose nanofiber-based phase change materials for thermal management.

Novel phase change materials composed of polyethylene glycol (PEG), cellulose nanofibers (CNFs) and carbon nanotubes (CNTs) were developed by an efficient and environment friendly strategy. The CNFs were modified and cross-linked by chitosan to form three-dimensional network structure, which provides strong support for the resulting CNF/CNT/PEG composites. The structure and properties of CNF/CNT/PEG composites were characterized using scanning electron microscopy, spectrums, and differential scanning calorimeter. They exhibit high latent heat (158.3 J/g), low heat loss (0.75%) and excellent photo-thermal conversion (energy storage efficiency 85.6%), electro-thermal conversion (energy storage efficiency 92.3%) properties. Due to their excellent performances, CNF/CNT/PEG composites have great potential to be used as thermal management materials.

Nanolignin-based high internal phase emulsions for efficient protection of curcumin against UV degradation.

As an emulsifier, lignin exhibits excellent UV resistance on drug-loaded emulsion systems for drug delivery. However, due to the structural variation and complexity of lignins from various origins, their UV shielding performance varies with the techniques for lignin extraction, which impacts properties and the protection efficiency of lignin-based HIPEs (high internal phase emulsions). In this work, lignin nanoparticles, prepared from three lignin preparations of Eucalyptus, were used in HIPEs delivery systems to protect curcumin from degradation by UV radiation. Structures of the lignin preparations were characterized using 2D HSQC (heteronuclear single-quantum coherence) NMR (nuclear magnetic resonance), 31P NMR, and GPC (gel permeation chromatography). The residual curcumin level after 36 h UV exposure in the nanolignin-based HIPEs was over 72 %, much higher than that (< 10 % after 24 h UV exposure) in the oil phase without lignin, indicating that the nanolignin-based HIPEs with enhanced UV shielding ability protect curcumin better. Of the three lignin preparations, AL (alkali lignin), with the lowest molecular weight, highest contents of phenolic hydroxyl and carboxyl groups, and highest S/G ratio, displayed the best anti-UV radiation ability and the most uniform nanoparticle size.

Bio-inspired synthesis of amino acids modified sulfated cellulose nanofibrils into multivalent viral inhibitors via the Mannich reaction.

Virus cross-infection via surfaces poses a serious threat to public health. Inspired by natural sulfated polysaccharides and antiviral peptides, we prepared multivalent virus blocking nanomaterials by introducing amino acids to sulfated cellulose nanofibrils (SCNFs) via the Mannich reaction. The antiviral activity of the resulting amino acid-modified sulfated nanocellulose was significantly improved. Specifically, 1 h treatment with arginine modified SCNFs at a concentration of 0.1 g/mL led to a complete inactivation of the phage-X174 (reduction by more than three orders of magnitude). Atomic force microscope showed that amino acid-modified sulfated nanofibrils can bind phage-X174 to form linear clusters, thus preventing the virus from infecting the host. When we coated wrapping paper and the inside of a face-mask with our amino acid-modified SCNFs, phage-X174 was completely deactivated on the coated surfaces, demonstrating the potential of our approach for use in the packaging and personal protective equipment industries. This work provides an environmentally friendly and cost-efficient approach to fabricating multivalent nanomaterials for antiviral applications.

Color-Tunable, Excitation-Dependent, and Water Stimulus-Responsive Room-Temperature Phosphorescence Cellulose for Versatile Applications.

Smart-response materials with ultralong room-temperature phosphorescence (RTP) are highly desirable, but they have rarely been described, especially those originating from sustainable polymers. Herein, a variety of cellulose derivatives with 1,4-dihydropyridine (DHP) rings are synthesized through the Hantzsch reaction, giving impressive RTP with a long lifetime of up to 1251 ms. Specifically, the introduction of acetoacetyl groups and DHP rings promotes the spin-orbit coupling and intersystem crossing process; and multiple interactions between cellulose induce clustering and inhibit the nonradiative transitions, boosting long-live RTP. Furthermore, the resulting transparent and flexible cellulose films also exhibit excitation-dependent and color-tunable afterglows by introducing different extended aromatic groups. More interestingly, the RTP performance of these films is sensitive to water and can be repeated in response to wet/dry stimuli. Inspired by these advantages, the RTP cellulose demonstrates advanced applications in information encryption and anti-counterfeiting. This work not only enriches the photophysical properties of cellulose but also provides a versatile platform for the development of sustainable afterglows.

Facile fabrication of cellulose-based hydrophobic paper via Michael addition reaction.

The inherent highly hydrophilic feature of cellulose-based paper hinders its application in many fields. Herein, a cellulose-based hydrophobic paper was fabricated based on surface chemical modification. Firstly, the hydrophobic acrylate components were bonded to the cellulose acetoacetate (CAA) fibers to obtain CAA graft acrylate (CAA-X) fibers through Michael addition reaction. Subsequently, CAA-X fibers were processed into paper via wet papermaking technology. The resulting paper exhibited good hydrophobic performance (water contact angle was up to 135°) with an air permeability of 24.8 µm/Pa·s. The hydrophobicity of paper was very stable and remained even after treating with different solvents. Moreover, the hydrophobic properties of this paper could be adjusted by changing the type of acrylate component. It should be noted that the surface modification strategy has no obvious effects on the whiteness (79.8%), writing, and printing properties of the cellulose fibers. Thus, it is a simple, benign, and efficient strategy for the construction of cellulose-based hydrophobic paper, which has great potential to be used in paper tableware, oil-water separation, watercolor protection, and food packaging fields.

Liquid metal and Mxene enable self-healing soft electronics based on double networks of bacterial cellulose hydrogels.

Liquid metal (LM) nanodroplets and MXene nanosheets are integrated with sulfonated bacterial nanocellulose (BNC) and acrylic acid (AA). Upon fast sonication, AA polymerization leads to a crosslinked composite hydrogel in which BNC exfoliates Mxene, forming organized conductive pathways. Soft conducting properties are achieved in the presence of colloidally stable core-shell LM nanodroplets. Due to the unique gelation mechanism and the effect of Mxene, the hydrogels spontaneously undergo surface wrinkling, which improves their electrical sensitivity (GF = 8.09). The hydrogels are further shown to display interfacial adhesion to a variety of surfaces, ultra-elasticity (tailorable elongation, from 1000 % to 3200 %), indentation resistance and self-healing capabilities. Such properties are demonstrated in wearable, force mapping, multi-sensing and patternable electroluminescence devices.