High-Performance and Moisture-Stable Cellulose–Starch Nanocomposites Based on Bioinspired Core–Shell Nanofibers

Recent Progress of Biodegradable Polymer Package Materials: Nanotechnology Improving Both Oxygen and Water Vapor Barrier Performance

Biodegradable polymers have become a topic of great scientific and industrial interest due to their environmentally friendly nature. For the benefit of the market economy and environment, biodegradable materials should play a more critical role in packaging materials, which currently account for more than 50% of plastic products. However, various challenges remain for biodegradable polymers for practical packaging applications. Particularly pertaining to the poor oxygen/moisture barrier issues, which greatly limit the application of current biodegradable polymers in food packaging. In this review, various strategies for barrier property improvement are summarized, such as chain architecture and crystallinity tailoring, melt blending, multi-layer co-extrusion, surface coating, and nanotechnology. These strategies have also been considered effective ways for overcoming the poor oxygen or water vapor barrier properties of representative biodegradable polymers in mainstream research.

A novel salt-barrier method of preparation flexible temperature resistant full-component nanocellulose membranes

With the simplification and diversification of separation technologies, nanocellulose membranes have become widely used as insulating materials. Recently, study of nanocellulose membrane modification has become a hot topic. However, the application of nanocellulose membrane has been limited due to their inadequate heat resistance and flexibility. Herein, based on the pyrolytic and thermoplastic properties of cellulose, we innovatively introduced a salt barrier scheme to regulate the degree of hydrogen bonding and thermoplastic bonding between fibers. This was achieved by adding a salt barrier agent, NaCl, in the middle of the nanocellulose to prepare and obtain flexible, high-temperature-resistant nanocellulose film materials. The full-component cellulose films thus prepared exhibited high tensile strength (8 MPa), excellent flexibility (105 mN), high electrical breakdown strength (67 KV/mm), and volume resistivity meeting the standard of insulation materials (3.23 × 1013 Ω·m). This scheme adheres to the principles of low cost, green, non-toxic and non-hazardous, providing a brand new approach for the research and development of high temperature resistant cellulose membrane materials, which is of significant commercial value and industrialization prospect.

Residual Strain and Nanostructural Effects during Drying of Nanocellulose/Clay Nanosheet Hybrids: Synchrotron X-ray Scattering Results

Cellulose nanofibrils (CNF) with 2D silicate nanoplatelet reinforcement readily form multifunctional composites by vacuum-assisted self-assembly from hydrocolloidal mixtures. The final nanostructure is formed during drying. The crystalline nature of CNF and montmorillonite (MTM) made it possible to use synchrotron X-ray scattering (WAXS, SAXS) to monitor structural development during drying from water and from ethanol. Nanostructural changes in the CNF and MTM crystals were investigated. Changes in the out-of-plane orientation of CNF and MTM were determined. Residual drying strains previously predicted from theory were confirmed in both cellulose and MTM platelets due to capillary forces. The formation of tactoid platelet stacks could be followed. We propose that after filtration, the constituent nanoparticles in the swollen, solid gel already have a "fixed" location, although self-assembly and ordering processes take place during drying.

Formation of Core-Sheath Polymer Fibers by Free Surface Spinning of Aqueous Two-Phase Systems

Core-sheath fibers have numerous applications ranging from composite materials for advanced manufacturing to materials for drug delivery and regenerative medicine. Here, a simple and tunable approach for the generation of core-sheath fibers from immiscible solutions of dextran and polyethylene oxide is described. This approach exploits the entanglement of polymer molecules within the dextran and polyethylene oxide phases for free surface spinning into dry fibers. The mechanism by which these core-sheath fibers are produced after contact with a solid substrate (such as a microneedle) involves complex flows of the phase-separating polymer solutions, giving rise to a liquid-liquid core-sheath flow that is drawn into a liquid bridge. This liquid bridge then elongates into a core-sheath fiber through extensional flow as the contacting substrate is withdrawn. The core-sheath structure of the fibers produced by this approach is confirmed by attenuated total reflection Fourier-transform infrared spectroscopy and confocal microscopy. Tuning of the core diameter is also demonstrated by varying the weight percentage of dextran added to the reservoir from which the fibers are formed.

Efficient Softening and Toughening Strategies of Cellulose Nanofibril Nanocomposites Using Comb Polyurethane

Cellulose nanofibrils (CNFs) have attracted attention as building blocks for sustainable materials owing to their high performance and the advantages of their abundant natural resources. Bioinspired CNF/polymer nanocomposites, consisting of a soft polymer phase and a high fraction (>50 wt %) of CNF reinforcement, have been focused on excellent mechanical properties, including Young's modulus, mechanical strength, and toughness, mimicking the energy dissipation system in nature. However, efficient softening and toughening with a small amount of the soft phase is still a challenge because a large amount of the polymer phase (nearly 50%) is still required to provide ductility and toughness. Here, we describe a topological strategy in the polymer phase for efficient toughening of bioinspired CNF nanocomposites with a water-soluble comb polyurethane (PU). The comb PU provided higher elongation at break and more efficient flexibility for the nanocomposite than the linear PU, even at a small content. Moreover, CNF nanocomposites with 30 wt % of PU content and tetrabutylammonium as bulky counterions showed enhanced toughness (180% higher) and strain at break (250% higher) when compared to pure CNF due to the promotion of slippage between nanofibrils. Scanning electron microscopy (SEM) images of the fracture surface for CNF/comb PU nanocomposites displayed the pull-out of mesoscale layers and nanofibrils, supporting that the comb topology promotes the slippage between fibrils. Furthermore, the rheological study revealed that the comb PU has an entanglement plateau modulus lower than linear PU by 1 order of magnitude, related to the loosened entanglements. Our study establishes an efficient softening and toughening strategy while using small amounts of polymer phase addition, promoting interfibrillar slippage with the loosely entangled comb PU phase.

Blends of sodium deoxycholate-based poly(ester ether)urethane ionomer and hydroxypropylcellulose with mucosal adhesiveness

New mucoadhesive blends of sodium deoxycholate-based poly(ester ether)urethane ionomer (PU) and hydroxypropyl cellulose (HPC) are prepared. The presence of the intermolecular interactions between the polymeric components has been investigated by FTIR spectroscopy indicating their miscibility in the solid phase. DSC studies also revealed a single glass transition of the blends, which is indicative of miscibility of PU and HPC in the amorphous phase. The amount of HPC in the blends influences strongly the physicochemical and mucoadhesion/bioadhesion properties. It was found that the value of area attributed to ordered hydrogen bonding (FTIR), the onset temperature values of thermal degradation in N₂ flow (TG/DTG), the values of the sorption capacity (Dynamic Vapor Sorption-DVS), the values of the apparent viscosity (rheological measurements) and mucoadhesion/bioadhesion properties increased by increasing the HPC content in the blends. Complex viscosity revealed shear thinning behavior for all the studied solutions evidencing the contributive role of polymer viscoelasticity on mucoadhesion. It was found that both G' and G" increase with an increase in angular frequency and G">G' which is characteristic for liquid-like (sol state) behavior for all blended solutions and this behavior is helpful in the adhesion with mucosa surface. Mucoadhesion of PU/HPC blends was assessed in the stomach mucosa at pH 2.6 and 37 °C. Bioadhesion test was performed at pH 7.4 and 37 °C and revealed a stronger interaction of PU/HPC blends with cellulose membrane than with stomach mucosa. The similar nature of the HPC and cellulose membrane determines additional adhesion forces and implicity high adhesion properties. The HPC component increases the hydrophilicity of the blends as DVS analysis revealed, but also leads to hydrolytic degradation. FTIR spectroscopy analysis was used to evaluate the hydrolytic stability in acid (pH 2.6) and slightly alkaline (pH 7.4) PBS media and a mechanism of degradation has been proposed.

Wood hemicelluloses exert distinct biomechanical contributions to cellulose fibrillar networks

Hemicelluloses, a family of heterogeneous polysaccharides with complex molecular structures, constitute a fundamental component of lignocellulosic biomass. However, the contribution of each hemicellulose type to the mechanical properties of secondary plant cell walls remains elusive. Here we homogeneously incorporate different combinations of extracted and purified hemicelluloses (xylans and glucomannans) from softwood and hardwood species into self-assembled networks during cellulose biosynthesis in a bacterial model, without altering the morphology and the crystallinity of the cellulose bundles. These composite hydrogels can be therefore envisioned as models of secondary plant cell walls prior to lignification. The incorporated hemicelluloses exhibit both a rigid phase having close interactions with cellulose, together with a flexible phase contributing to the multiscale architecture of the bacterial cellulose hydrogels. The wood hemicelluloses exhibit distinct biomechanical contributions, with glucomannans increasing the elastic modulus in compression, and xylans contributing to a dramatic increase of the elongation at break under tension. These diverging effects cannot be explained solely from the nature of their direct interactions with cellulose, but can be related to the distinct molecular structure of wood xylans and mannans, the multiphase architecture of the hydrogels and the aggregative effects amongst hemicellulose-coated fibrils. Our study contributes to understanding the specific roles of wood xylans and glucomannans in the biomechanical integrity of secondary cell walls in tension and compression and has significance for the development of lignocellulosic materials with controlled assembly and tailored mechanical properties.

Hemicelluloses are an essential constituent of plant cell walls, but the individual biomechanical roles remain elusive. Here the authors report on the interaction of wood hemicellulose with bacterial cellulose during deposition and explore the resultant fibrillar architecture and mechanical properties.

Best Practice for Reporting Wet Mechanical Properties of Nanocellulose-Based Materials

Nanocellulose-based materials and nanocomposites show extraordinary mechanical properties with high stiffness, strength, and toughness. Although the last decade has witnessed great progress in understanding the mechanical properties of these materials, a crucial challenge is to identify pathways to introduce high wet strength, which is a critical parameter for commercial applications. Because of the waterborne fabrication methods, nanocellulose-based materials are prone to swelling by both adsorption of moist air or liquid water. Unfortunately, there is currently no best practice on how to take the swelling into account when reporting mechanical properties at different relative humidity or when measuring the mechanical properties of fully hydrated materials. This limits and in parts fully prevents comparisons between different studies. We review current approaches and propose a best practice for measuring and reporting mechanical properties of wet nanocellulose-based materials, highlighting the importance of swelling and the correlation between mechanical properties and volume expansion.

An Organic/Inorganic Nanocomposite of Cellulose Nanofibers and ZnO Nanorods for Highly Sensitive, Reliable, Wireless, and Wearable Multifunctional Sensor Applications

Organic and inorganic one-dimensional nanomaterials were synthesized and combined into a nanocomposite film for a wearable sensor. Reproducible ZnO nanorod (NR) synthesis was achieved by the addition of an appropriate amount of water. Cellulose nanofibers (CNFs) were used due to their porous matrix formation. The interconnected channels of brittle ZnO NRs were well-fabricated in the flexible network of CNFs. The surface morphology, thermal, and mechanical properties of the CNF/ZnO NR nanocomposite film were characterized. The interfacial interactions between these two nanomaterials were also studied. The nanocomposite film is sufficiently flexible so that it shows no electrical resistance changes even after repeated bending tests with a minimum bending radius of 1.5 mm. In addition, ZnO NRs with different lengths were synthesized. The composite of longer ZnO NRs and CNF showed 2.8 × 10³ times higher photocurrent and responsivity performance. The humidity sensing performance of the composite was also suggested. The CNF/ZnO NR film shows reasonable electrical signal changes enabling the evaluation of a calibration curve. Finally, a smart band including a CNF/ZnO NR film sensor was fabricated and connected to a smartphone by Bluetooth. These results open an avenue for developing wearable sensors by overcoming the brittleness of inorganic materials.

Effects of Cellulose Nanocrystals and Cellulose Nanofibers on the Structure and Properties of Polyhydroxybutyrate Nanocomposites

One of the major obstacles for polyhydroxybutyrate (PHB), a biodegradable and biocompatible polymer, in commercial applications is its poor elongation at break (~3%). In this study, the effects of nanocellulose contents and their types, including cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) on the crystallization, thermal, and mechanical properties of PHB composites were systematically compared. We explored the toughening mechanisms of PHB by adding CNCs and cellulose CNFs. The results showed that when the morphology of bagasse nanocellulose was rod-like and its content was 1 wt %, the toughening modification of PHB was the best. Compared with pure PHB, the elongation at break and Young’s modulus increased by 91.2% and 18.4%, respectively. Cellulose nanocrystals worked as heterogeneous nucleating agents in PHB and hence reduced its crystallinity and consequently improved the toughness of PHB. This simple approach could potentially be explored as a strategy to extend the possible applications of this biopolymer in packaging fields.

Core-Shell Fibers: Design, Roles, and Controllable Release Strategies in Tissue Engineering and Drug Delivery

The key attributes of core-shell fibers are their ability to preserve bioactivity of incorporated-sensitive biomolecules (such as drug, protein, and growth factor) and subsequently control biomolecule release to the targeted microenvironments to achieve therapeutic effects. Such qualities are highly favorable for tissue engineering and drug delivery, and these features are not able to be offered by monolithic fibers. In this review, we begin with an overview on design requirement of core-shell fibers, followed by the summary of recent preparation methods of core-shell fibers, with focus on electrospinning-based techniques and other newly discovered fabrication approaches. We then highlight the importance and roles of core-shell fibers in tissue engineering and drug delivery, accompanied by thorough discussion on controllable release strategies of the incorporated bioactive molecules from the fibers. Ultimately, we touch on core-shell fibers-related challenges and offer perspectives on their future direction towards clinical applications.

The Impact of Lignin Structural Diversity on Performance of Cellulose Nanofiber (CNF)-Starch Composite Films

Lignin fractions having different molecular weights and varied chemical structures isolated from kraft lignins of both softwood and hardwood via a sequential solvent fractionation technique were incorporated into a tunicate cellulose nanofibers (CNF)—starch mixture to prepare 100% bio-based composite films. The aim was to investigate the impact of lignin structural diversity on film performance. It was confirmed that lignin’s distribution in the films was dependent on the polarity of solvents used for fractionation (acetone > methanol > ethanol > ethyl acetate) and influenced the optical properties of the films. The –OH group content and molecular weight of lignin were positively related to film density. In general, the addition of lignin fractions led to decrease in thermal stability and increase in Young’s modulus of the composite films. The modulus of the films was found to decrease as the molecular weight of lignin increased, and a higher amount of carboxyl and phenolic –OH groups in the lignin fraction resulted in films with higher stiffness. The thermal analysis showed higher char content formation for lignin-containing films in a nitrogen atmosphere with increased molecular weight. In an oxygen atmosphere, the phenol content, saturated side chains and short chain structures of lignin had impacts on the maximum decomposition temperature of the films, confirming the relationship between the chemical structure of lignin and thermo-oxidative stability of the corresponding film. This study addresses the importance of lignin diversities on composite film performance, which could be helpful for tailoring lignin’s applications in bio-based materials based on their specific characteristics.

Sugar palm nanofibrillated cellulose (Arenga pinnata (Wurmb.) Merr): Effect of cycles on their yield, physic-chemical, morphological and thermal behavior

Nanofibrillated cellulose (NFCs) were extracted from sugar palm fibres (SPS) in two separate stages; delignification and mercerization to remove lignin and hemicellulose, respectively. Subsequently, the obtained cellulose fibres were then mechanically extracted into nanofibres using high pressurized homogenization (HPH). The diameter distribution sizes of the isolated nanofibres were dependent on the cycle number of HPH treatment. TEM micro-images displayed the decreasing trend of NFCs diameter, from 21.37 to 5.5 nm when the number of cycle HPH was increased from 5 to 15 cycles, meanwhile TGA and XRD analysis showed that the degradation temperature and crystallinity of the NFCs were slightly increased from 347 to 347.3 °C and 75.38 to 81.19% respectively, when the number of cycles increased. Others analysis also were carried on such as FT-IR, FESEM, AFM, physical properties, zeta potential and yield analysis. The isolated NFCs may be potentially applied in various application, such as tissue engineering scaffolds, bio-nanocomposites, filtration media, bio-packaging and etc.

Use of Ginger Nanofibers for the Preparation of Cellulose Nanocomposites and Their Antimicrobial Activities

Ginger residues left after the extraction of active ingredients from ginger rhizomes are considered to be a bio-waste, available in abundance and very rarely used. Extraction and isolation of natural nanofibers from the agro-waste is economical, environmentally benign, and an alternate strategy to replace synthetic fibers. Here, we report, for the first time, the isolation of ginger nanofibers (GNF) from ginger rhizomes spent by acid hydrolysis and followed by high-pressure homogenization. Scanning electron microscopy was utilized to identify the surface morphology of the GNF and the widths ranged between 130 to 200 nm. Structural analysis of GNF was identified by Fourier transform infrared spectroscopy, Differential scanning calorimetry, and X-ray diffraction methods. This GNF was used to make natural nanocomposites by the solvent-casting method reinforcement, using potato starch (PS) and tapioca starch (TS), and was characterized through various methods. These composites were prepared by the addition of 1, 3, 5, and 7 weight % of GNF with PS or TS. Among these, 5% of the GNF composites of these starches showed very high mechanical properties. The antibacterial test showed that the bionanocomposites with 5% GNF exhibited good antibacterial activity against Bacillus cereus, Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium, due to the addition of GNF in the biopolymer matrices. The viable use of GNF from the unexploited ginger agro-waste would create additional profit and it would help to diminish a large amount of waste generation. Thus, the developed bio-composite could also be employed for development of packing materials and be used in medical applications, such as wound healing pads and medical disposables.

Preserving Cellulose Structure: Delignified Wood Fibers for Paper Structures of High Strength and Transparency

To expand the use of renewable materials, paper products with superior mechanical and optical properties are needed. Although beating, bleaching, and additives are known to improve industrially produced Kraft pulp papers, properties are limited by the quality of the fibers. While the use of nanocellulose has been shown to significantly increase paper properties, the current cost associated with their production has limited their industrial relevance. Here, using a simple mild peracetic acid (PAA) delignification process on spruce, we produce hemicellulose-rich holocellulose fibers (28.8 wt %) with high intrinsic strength (1200 MPa for fibers with microfibrillar angle smaller than 10°). We show that PAA treatment causes less cellulose/hemicellulose degradation and better preserves cellulose nanostructure in comparison to conventional Kraft pulping. High-density holocellulose papers with superior mechanical properties (Young's modulus of 18 GPa and ultimate strength of 195 MPa) are manufactured using a water-based hot-pressing process, without the use of beating or additives. We propose that the preserved hemicelluloses act as "glue" in the interfiber region, improving both mechanical and optical properties of papers. Holocellulose fibers may be affordable and applicable candidates for making special paper/composites where high mechanical performance and/or optical transmittance are of interest.

Current progress in production of biopolymeric materials based on cellulose, cellulose nanofibers, and cellulose derivatives

Cellulose has attracted considerable attention as the strongest potential candidate feedstock for bio-based polymeric material production. During the past decade, significant progress in the production of biopolymers based on different cellulosic forms has been achieved. This review highlights the most recent advances and developments in the three main routes for the production of cellulose-based biopolymers, and discusses their scope and applications. The use of cellulose fibers, nanocellulose, and cellulose derivatives as fillers or matrices in biocomposite materials is an efficient biosustainable alternative for the production of high-quality polymer composites and functional polymeric materials. The use of cellulose-derived monomers (glucose and other platform chemicals) in the synthesis of sustainable biopolymers and functional polymeric materials not only provides viable replacements for most petroleum-based polymers but also enables the development of novel polymers and functional polymeric materials. The present review describes the current status of biopolymers based on various forms of cellulose and the scope of their importance and applications. Challenges, promising research trends, and methods for dealing with challenges in exploitation of the promising properties of different forms of cellulose, which are vital for the future of the global polymeric industry, are discussed. Sustainable cellulosic biopolymers have potential applications not only in the replacement of existing petroleum-based polymers but also in cellulosic functional polymeric materials for a range of applications from electrochemical and energy-storage devices to biomedical applications.

Template-Guided Assembly of Silk Fibroin on Cellulose Nanofibers for Robust Nanostructures with Ultrafast Water Transport

The construction of multilength scaled hierarchical nanostructures from diverse natural components is critical in the progress toward all-natural nanocomposites with structural robustness and versatile added functionalities. Here, we report a spontaneous formation of peculiar "shish kebab" nanostructures with the periodic arrangement of silk fibroin domains along straight segments of cellulose nanofibers. We suggest that the formation of these shish kebab nanostructures is facilitated by the preferential organization of heterogeneous (β-sheets and amorphous silk) domains along the cellulose nanofiber driven by modulated axial distribution of crystalline planes, hydrogen bonding, and hydrophobic interactions as suggested by all-atom molecular dynamic simulations. Such shish kebab nanostructures enable the ultrathin membrane to possess open, transparent, mechanically robust interlocked networks with high mechanical performance with up to 30 GPa in stiffness and 260 MPa in strength. These nanoporous robust membranes allow for the extremely high water flux, up to 3.5 × 10⁴ L h^-1 m^-2 bar^-1 combined with high rejection rate for various organic molecules, capability of capturing heavy metal ions and their further reduction into metal nanoparticles for added SERS detection capability and catalytic functionalities.

High-Strength Nanocomposite Aerogels of Ternary Composition: Poly(vinyl alcohol), Clay, and Cellulose Nanofibrils

Clay aerogels are foam-like materials with potential to combine high mechanical performance with fire retardancy. However, the compression strength of these aerogels is much lower than theoretically predicted values. High-strength aerogels with more than 95% porosity were prepared from a ternary material system based on poly(vinyl alcohol), montmorillonite clay platelets, and cellulose nanofibrils. A hydrocolloidal suspension of the three components was subjected to freeze-drying so that a low-density aerogel foam was formed. Cell structure was studied by field-emission scanning electron microscopy. Interactions at the molecular scale were observed by X-ray diffraction and Fourier transform infrared spectroscopy. Cross-linking was carried out using glutaraldehyde or borax, and moisture stability was investigated. These biobased ternary aerogels showed compression strength much better than that of previously studied materials and also showed strength higher than that of high-performance sandwich foam cores such as cross-linked polyvinyl chloride foams.

Extraction and modification of cellulose nanofibers derived from biomass for environmental application

Cellulose nanofibers obtained from various plants and microbial sources, their extraction methods and various environmental applications are discussed.

High wet-strength, thermally stable and transparent TEMPO-oxidized cellulose nanofibril film via cross-linking with poly-amide epichlorohydrin resin

TEMPO-oxidized cellulose nanofibrils (TOCNs) films cross-linked with different dosages of polyamide epichlorohydrin resin (PAE) show a great water-resistance and thermal stability.

Nanocellulose, a tiny fiber with huge applications

Nanocellulose is of increasing interest for a range of applications relevant to the fields of material science and biomedical engineering due to its renewable nature, anisotropic shape, excellent mechanical properties, good biocompatibility, tailorable surface chemistry, and interesting optical properties. We discuss the main areas of nanocellulose research: photonics, films and foams, surface modifications, nanocomposites, and medical devices. These tiny nanocellulose fibers have huge potential in many applications, from flexible optoelectronics to scaffolds for tissue regeneration. We hope to impart the readers with some of the excitement that currently surrounds nanocellulose research, which arises from the green nature of the particles, their fascinating physical and chemical properties, and the diversity of applications that can be impacted by this material.

Probing Anisotropic Surface Properties of Molybdenite by Direct Force Measurements

Probing anisotropic surface properties of layer-type mineral is fundamentally important in understanding its surface charge and wettability for a variety of applications. In this study, the surface properties of the face and the edge surfaces of natural molybdenite (MoS2) were investigated by direct surface force measurements using atomic force microscope (AFM). The interaction forces between the AFM tip (Si3N4) and face or edge surface of molybdenite were measured in 10 mM NaCl solutions at various pHs. The force profiles were well-fitted with classical DLVO (Derjaguin-Landau-Verwey-Overbeek) theory to determine the surface potentials of the face and the edge surfaces of molybdenite. The surface potentials of both the face and edge surfaces become more negative with increasing pH. At neutral and alkaline conditions, the edge surface exhibits more negative surface potential than the face surface, which is possibly due to molybdate and hydromolybdate ions on the edge surface. The point of zero charge (PZC) of the edge surface was determined around pH 3 while PZC of the face surface was not observed in the range of pH 3-11. The interaction forces between octadecyltrichlorosilane-treated AFM tip (OTS-tip) and face or edge surface of molybdenite were also measured at various pHs to study the wettability of molybdenite surfaces. An attractive force between the OTS-tip and the face surface was detected. The force profiles were well-fitted by considering DLVO forces and additional hydrophobic force. Our results suggest the hydrophobic feature of the face surface of molybdenite. In contrast, no attractive force between the OTS-tip and the edge surface was detected. This is the first study in directly measuring surface charge and wettability of the pristine face and edge surfaces of molybdenite through surface force measurements.

Holocellulose Nanofibers of High Molar Mass and Small Diameter for High-Strength Nanopaper

Wood cellulose nanofibers (CNFs) based on bleached pulp are different from the cellulose microfibrils in the plant cell wall in terms of larger diameter, lower cellulose molar mass, and modified cellulose topochemistry. Also, CNF isolation often requires high-energy mechanical disintegration. Here, a new type of CNFs is reported based on a mild peracetic acid delignification process for spruce and aspen fibers, followed by low-energy mechanical disintegration. Resulting CNFs are characterized with respect to geometry (AFM, TEM), molar mass (SEC), and polysaccharide composition. Cellulose nanopaper films are prepared by filtration and characterized by UV-vis spectrometry for optical transparency and uniaxial tensile tests. These CNFs are unique in terms of high molar mass and cellulose-hemicellulose core-shell structure. Furthermore, the corresponding nanopaper structures exhibit exceptionally high optical transparency and the highest mechanical properties reported for comparable CNF nanopaper structures.

Highly alkynyl-functionalization of cellulose nanocrystals and advanced nanocomposites thereof via click chemistry

Advanced nanocomposites were developed from alkynylated cellulose nanocrystals and the reactive polymer matrix via Huisgen click chemistry.