Nanoscale cellulose films with different crystallinities and mesostructures--their surface properties and interaction with water

Controlled Interlayer Binding and Healing Improve the Transverse Properties of Upcycled Disposable Waste Wood

Recovery and reuse of bulk waste wood are particularly challenging because of usage defects and contaminations. Here, we present a robust and efficient strategy for regenerating used wood veneers into high-performance structural materials through micro/nano interface manipulation. Our approach involves using cellulose-based interlayers to bind together two waste wood plates without an external adhesive by partially dissolving and regenerating the interlayer using a solution of ionic liquids and dimethyl sulfoxide. The mechanical properties of the regenerated wood exceed that of natural wood, displaying over a 16 and 20 times increase in transverse tensile strength and modulus, respectively, and 4-6 times improvement in longitudinal tensile strength and modulus. Nanoscale mechanical analyses show that the improvement is possible as a result of several factors, including the robust network structure of the interlayer, the good adhesion at the wood-interlayer interface, the compacted wood structure, and the low stiffness and deformation gradients between the interlayer and the wood structure. The interlayers can be created from waste papers and wood particles by taking advantage of the nanofibrillar structure of cellulose.

Development of high-barrier composite films for sustainable reduction of non-biodegradable materials in food packaging application

Widely employed petroleum-based food packaging materials have inflicted irreparable harm on ecosystems, primarily stemming from their non-biodegradable attributes and recycling complexities. Inspired by natural nacre with a layered aragonite platelet/nanofiber/protein multi-structure, we prepared high-barrier composite films by self-assembly of cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), montmorillonite (MMT), polyvinyl alcohol (PVA) and alkyl ketene dimer (AKD). The composite films demonstrated outstanding barrier properties with oxygen vapor transmission of 0.193 g·mm·m-2·day-1 and water vapor transmission rates of 0.062 cm3·mm·m-2·day-1·0.1 MPa-1, which were significantly lower than those of most biomass-degradable packaging materials. Additionally, the impacts of mixing nanocellulose with various aspect ratios on the tensile strength and folding cycles of the films were examined. The exceptional resistance of the composite films to oil and water provides a novel and sustainable approach to reduce non-biodegradable plastic packaging.

Conceptualizing flexible papers using cellulose model surfaces and polymer particles

Cellulose, as a naturally abundant and biocompatible material, is still gaining interest due to its high potential for functionalization. This makes cellulose a promising candidate for replacing plastics. Understanding how cellulose interacts with various additives is crucial for creating composite materials with diverse properties, as it is the case for plastics. In addition, the mechanical properties of the composite materials are assumed to be related to the mobility of the additives against the cellulose. Using a well-defined cellulose model surface (CMS), we aim to understand the adsorption and desorption of two polymeric particles (core-shell particles and microgels) to/from the cellulose surface. The nanomechanics of particles and CMS are quantified by indentation measurements with an atomic force microscope (AFM). AFM topography measurements quantified particle adsorption and desorption on the CMS, while peak force AFM measurements determined the force needed to move individual particles. Both particles and the CMS exhibited pH-dependent charge behavior, allowing a tunable interaction between them. Particle adsorption was irreversible and driven by electrostatic forces. In contrast, desorption and particle mobility forces are dominated by structural morphology. In addition, we found that an annealing procedure consisting of swelling/drying cycles significantly increased the adhesion strength of both particles. Using the data, we achieve a deeper understanding of the interaction of cellulose with polymeric particles, with the potential to advance the development of functional materials and contribute to various fields, including smart packaging, sensors, and biomedical applications.

Protein Adsorption and Its Effects on Electroanalytical Performance of Nanocellulose/Carbon Nanotube Composite Electrodes

Protein fouling is a critical issue in the development of electrochemical sensors for medical applications, as it can significantly impact their sensitivity, stability, and reliability. Modifying planar electrodes with conductive nanomaterials that possess a high surface area, such as carbon nanotubes (CNTs), has been shown to significantly improve fouling resistance and sensitivity. However, the inherent hydrophobicity of CNTs and their poor dispersibility in solvents pose challenges in optimizing such electrode architectures for maximum sensitivity. Fortunately, nanocellulosic materials offer an efficient and sustainable approach to achieving effective functional and hybrid nanoscale architectures by enabling stable aqueous dispersions of carbon nanomaterials. Additionally, the inherent hygroscopicity and fouling-resistant nature of nanocellulosic materials can provide superior functionalities in such composites. In this study, we evaluate the fouling behavior of two nanocellulose (NC)/multiwalled carbon nanotube (MWCNT) composite electrode systems: one using sulfated cellulose nanofibers and another using sulfated cellulose nanocrystals. We compare these composites to commercial MWCNT electrodes without nanocellulose and analyze their behavior in physiologically relevant fouling environments of varying complexity using common outer- and inner-sphere redox probes. Additionally, we use quartz crystal microgravimetry with dissipation monitoring (QCM-D) to investigate the behavior of amorphous carbon surfaces and nanocellulosic materials in fouling environments. Our results demonstrate that the NC/MWCNT composite electrodes provide significant advantages for measurement reliability, sensitivity, and selectivity over only MWCNT-based electrodes, even in complex physiological monitoring environments such as human plasma.

Bioderived Laser-Induced Graphene for Sensors and Supercapacitors

The maskless and chemical-free conversion and patterning of synthetic polymer precursors into laser-induced graphene (LIG) via laser-induced pyrolysis is a relatively new but growing field. Bioderived precursors from lignocellulosic materials can also be converted to LIG, opening a path to sustainable and environmentally friendly applications. This review is designed as a starting point for researchers who are not familiar with LIG and/or who wish to switch to sustainable bioderived precursors for their applications. Bioderived precursors are described, and their performances (mainly crystallinity and sheet resistance of the obtained LIG) are compared. The three main fields of application are reviewed: supercapacitors and electrochemical and physical sensors. The key advantages and disadvantages of each precursor for each application are discussed and compared to those of a benchmark of polymer-derived LIG. LIG from bioderived precursors can match, or even outperform, its synthetic analogue and represents a viable and sometimes better alternative, also considering its low cost and biodegradability.

Harnessing Nature's Ingenuity: A Comprehensive Exploration of Nanocellulose from Production to Cutting-Edge Applications in Engineering and Sciences

Primary material supply is the heart of engineering and sciences. The depletion of natural resources and an increase in the human population by a billion in 13 to 15 years pose a critical concern regarding the sustainability of these materials; therefore, functionalizing renewable materials, such as nanocellulose, by possibly exploiting their properties for various practical applications, has been undertaken worldwide. Nanocellulose has emerged as a dominant green natural material with attractive and tailorable physicochemical properties, is renewable and sustainable, and shows biocompatibility and tunable surface properties. Nanocellulose is derived from cellulose, the most abundant polymer in nature with the remarkable properties of nanomaterials. This article provides a comprehensive overview of the methods used for nanocellulose preparation, structure-property and structure-property correlations, and the application of nanocellulose and its nanocomposite materials. This article differentiates the classification of nanocellulose, provides a brief account of the production methods that have been developed for isolating nanocellulose, highlights a range of unique properties of nanocellulose that have been extracted from different kinds of experiments and studies, and elaborates on nanocellulose potential applications in various areas. The present review is anticipated to provide the readers with the progress and knowledge related to nanocellulose. Pushing the boundaries of nanocellulose further into cutting-edge applications will be of particular interest in the future, especially as cost-effective commercial sources of nanocellulose continue to emerge.

Cellulose nanofiber-reinforced solid polymer electrolytes with high ionic conductivity for lithium batteries

Lithium-metal electrodes are promising for developing next-generation lithium-based batteries with high energy densities. However, their implementation is severely limited by dendritic growth during battery cycling, which eventually short-circuits the battery. Replacing conventional liquid electrolytes with solid polymer electrolytes (SPEs) can suppress dendritic growth. Unfortunately, in SPEs the high stiffness required for suppressing dendrites comes at the expense of efficient lithium-ion transport. Some polymer-based composite electrolytes, however, enable the decoupling of stiffness and ionic conductivity. This study introduces a composite SPE comprised of a relatively soft poly(ethylene oxide-co-epichlorohydrin) (EO-co-EPI) statistical copolymer with high ionic conductivity and cellulose nanofibers (CNFs), a filler with extraordinary stiffness sourced from abundant cellulose. CNF-reinforcement of EO-co-EPI increases the storage modulus up to three orders of magnitude while essentially maintaining the SPE's high ionic conductivity. The composite SPE exhibits good cycling ability and electrochemical stability, demonstrating its utility in lithium metal batteries.

The Colloidal Properties of Nanocellulose

Nanocelluloses are anisotropic nanoparticles of semicrystalline assemblies of glucan polymers. They have great potential as renewable building blocks in the materials platform of a more sustainable society. As a result, the research on nanocellulose has grown exponentially over the last decades. To fully utilize the properties of nanocelluloses, a fundamental understanding of their colloidal behavior is necessary. As elongated particles with dimensions in a critical nanosize range, their colloidal properties are complex, with several behaviors not covered by classical theories. In this comprehensive Review, we describe the most prominent colloidal behaviors of nanocellulose by combining experimental data and theoretical descriptions. We discuss the preparation and characterization of nanocellulose dispersions, how they form networks at low concentrations, how classical theories cannot describe their behavior, and how they interact with other colloids. We then show examples of how scientists can use this fundamental knowledge to control the assembly of nanocellulose into new materials with exceptional properties. We hope aspiring and established researchers will use this Review as a guide.

The Influence of Cellulose Nanocrystal Characteristics on Regenerative Silk Composite Fiber Properties

Cellulose nanocrystals (CNCs), obtained from natural resources, possess great potential as a bioderived reinforcement for natural-fiber-reinforced composites (NFRPs) due to their superior crystallinity and high aspect ratio. To elucidate the specific parameters of CNCs that significantly affect their mechanical performance, various CNCs were investigated to fabricate high-performance nanocomposite fibers together with regenerated silk fibroin (RSF). We confirmed that the high aspect ratio (~9) of the CNCs was the critical factor to increase the tensile strength and stiffness rather than the crystallinity. At a 1 vol% of CNCs, the strength and stiffness reached ~300 MPa and 10.5 GPa, respectively, which was attributed not only to a stable dispersion but also to alignment. This approach has the potential to evaluate the parameters of natural reinforcement and may also be useful in constructing high-performance NFRPs.

Understanding Nanocellulose-Water Interactions: Turning a Detriment into an Asset

Modern technology has enabled the isolation of nanocellulose from plant-based fibers, and the current trend focuses on utilizing nanocellulose in a broad range of sustainable materials applications. Water is generally seen as a detrimental component when in contact with nanocellulose-based materials, just like it is harmful for traditional cellulosic materials such as paper or cardboard. However, water is an integral component in plants, and many applications of nanocellulose already accept the presence of water or make use of it. This review gives a comprehensive account of nanocellulose-water interactions and their repercussions in all key areas of contemporary research: fundamental physical chemistry, chemical modification of nanocellulose, materials applications, and analytical methods to map the water interactions and the effect of water on a nanocellulose matrix.

Biobased Nanomaterials─The Role of Interfacial Interactions for Advanced Materials

This review presents recent advances regarding biomass-based nanomaterials, focusing on their surface interactions. Plant biomass-based nanoparticles, like nanocellulose and lignin from industry side streams, hold great potential for the development of lightweight, functional, biodegradable, or recyclable material solutions for a sustainable circular bioeconomy. However, to obtain optimal properties of the nanoparticles and materials made thereof, it is crucial to control the interactions both during particle production and in applications. Herein we focus on the current understanding of these interactions. Solvent interactions during particle formation and production, as well as interactions with water, polymers, cells and other components in applications, are addressed. We concentrate on cellulose and lignin nanomaterials and their combination. We demonstrate how the surface chemistry of the nanomaterials affects these interactions and how excellent performance is only achieved when the interactions are controlled. We furthermore introduce suitable methods for probing interactions with nanomaterials, describe their advantages and challenges, and introduce some less commonly used methods and discuss their possible applications to gain a deeper understanding of the interfacial chemistry of biobased nanomaterials. Finally, some gaps in current understanding and interesting emerging research lines are identified.

Elucidating the fine-scale structural morphology of nanocellulose by nano infrared spectroscopy

Nanoscale infrared (IR) spectroscopy and microscopy, enabling the acquisition of IR spectra and images with a lateral resolution of 20 nm, is employed to chemically characterize individual cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) to elucidate if the CNCs and CNFs consist of alternating crystalline and amorphous domains along the CNF/CNC. The high lateral resolution enables studies of the nanoscale morphology at different domains of the CNFs/CNCs: flat segments, kinks, twisted areas, and end points. The types of nanocellulose investigated are CNFs from tunicate, CNCs from cotton, and anionic and cationic wood-derived CNFs. All nano-FTIR spectra acquired from the different samples and different domains of the individual nanocellulose particles resemble a spectrum of crystalline cellulose, suggesting that the non-crystalline cellulose signal observed in macroscopic measurements of nanocellulose most likely originate from cellulose chains present at the surface of the nanocellulose particles.

Nanocellulosics in Transient Technology

Envisage a world where discarded electrical/electronic devices and single-use consumables can dematerialize and lapse into the environment after the end-of-useful life without constituting health and environmental burdens. As available resources are consumed and human activities build up wastes, there is an urgency for the consolidation of efforts and strategies in meeting current materials needs while assuaging the concomitant negative impacts of conventional materials exploration, usage, and disposal. Hence, the emerging field of transient technology (Green Technology), rooted in eco-design and closing the material loop toward a friendlier and sustainable materials system, holds enormous possibilities for assuaging current challenges in materials usage and disposability. The core requirements for transient materials are anchored on meeting multicomponent functionality, low-cost production, simplicity in disposability, flexibility in materials fabrication and design, biodegradability, biocompatibility, and environmental benignity. In this regard, biorenewables such as cellulose-based materials have demonstrated capacity as promising platforms to fabricate scalable, renewable, greener, and efficient materials and devices such as membranes, sensors, display units (for example, OLEDs), and so on. This work critically reviews the recent progress of nanocellulosic materials in transient technologies toward mitigating current environmental challenges resulting from traditional material exploration, usage, and disposal. While spotlighting important fundamental properties and functions in the material selection toward practicability and identifying current difficulties, we propose crucial research directions in advancing transient technology and cellulose-based materials in closing the loop for conventional materials and sustainability.

The influence of temperature on cellulose swelling at constant water density

We have in this paper investigated how water sorbs to cellulose. We found that both cellulose nanofibril (CNF) and cellulose nanocrystal (CNC) films swell similarly, as they are both mainly composed of cellulose. CNF/CNC films subjected to water at 0.018 kg/m³ at 25 °C and 39 °C, showed a decrease in swelling from ~ 8 to 2%. This deswelling increased the tensile index of CNF-films by ~ 13%. By molecular modeling of fibril swelling, we found that water sorbed to cellulose exhibits a decreased diffusion constant compared to bulk water. We quantified this change and showed that diffusion of sorbed water displays less dependency on swelling temperature compared to bulk water diffusion. To our knowledge, this has not previously been demonstrated by molecular modeling. The difference between bulk water diffusion (D_WW) and diffusion of water sorbed to cellulose (D_CC) increased from D_WW - D_CC ~ 3 × 10^-5 cm/s² at 25 °C to D_WW - D_CC ~ 8.3 × 10^-5 cm/s² at 100 °C. Moreover, water molecules spent less successive time sorbed to a fibril at higher temperatures.

Acoustic force spectroscopy reveals subtle differences in cellulose unbinding behavior of carbohydrate-binding modules

Protein adsorption to solid carbohydrate interfaces is critical to many biological processes, particularly in biomass deconstruction. To engineer more-efficient enzymes for biomass deconstruction into sugars, it is necessary to characterize the complex protein-carbohydrate interfacial interactions. A carbohydrate-binding module (CBM) is often associated with microbial surface-tethered cellulosomes or secreted cellulase enzymes to enhance substrate accessibility. However, it is not well known how CBMs recognize, bind, and dissociate from polysaccharides to facilitate efficient cellulolytic activity, due to the lack of mechanistic understanding and a suitable toolkit to study CBM-substrate interactions. Our work outlines a general approach to study the unbinding behavior of CBMs from polysaccharide surfaces using a highly multiplexed single-molecule force spectroscopy assay. Here, we apply acoustic force spectroscopy (AFS) to probe a Clostridium thermocellum cellulosomal scaffoldin protein (CBM3a) and measure its dissociation from nanocellulose surfaces at physiologically relevant, low force loading rates. An automated microfluidic setup and method for uniform deposition of insoluble polysaccharides on the AFS chip surfaces are demonstrated. The rupture forces of wild-type CBM3a, and its Y67A mutant, unbinding from nanocellulose surfaces suggests distinct multimodal CBM binding conformations, with structural mechanisms further explored using molecular dynamics simulations. Applying classical dynamic force spectroscopy theory, the single-molecule unbinding rate at zero force is extrapolated and found to agree with bulk equilibrium unbinding rates estimated independently using quartz crystal microbalance with dissipation monitoring. However, our results also highlight critical limitations of applying classical theory to explain the highly multivalent binding interactions for cellulose-CBM bond rupture forces exceeding 15 pN.

Nanocellulose-Based Composite Materials Used in Drug Delivery Systems

Nanocellulose has lately emerged as one of the most promising "green" materials due to its unique properties. Nanocellulose can be mainly divided into three types, i.e., cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and bacterial cellulose (BC). With the rapid development of technology, nanocellulose has been designed into multidimensional structures, including 1D (nanofibers, microparticles), 2D (films), and 3D (hydrogels, aerogels) materials. Due to its adaptable surface chemistry, high surface area, biocompatibility, and biodegradability, nanocellulose-based composite materials can be further transformed as drug delivery carriers. Herein, nanocellulose-based composite material used for drug delivery was reviewed. The typical drug release behaviors and the drug release mechanisms of nanocellulose-based composite materials were further summarized, and the potential application of nanocellulose-based composite materials was prospected as well.

Value-Added Utilization of Wheat Straw: From Cellulose and Cellulose Nanofiber to All-Cellulose Nanocomposite Film

To accelerate the high value-added usage of agricultural residue, cellulose and cellulose nanofibers (CNFs) were extracted from wheat straw and then formed into all-cellulose nanocomposite films. The acid-alkali method (AM) and the extraction method (EM) were respectively adopted to prepare wheat straw cellulose (WSC), and the TEMPO oxidation method was used to extract CNFs. The nanocomposite films were fabricated by dissolving WSC and adding different CNF contents of 0.0, 0.5, 1.5, and 3.0%. There was a better miscibility for the all-cellulose nanocomposite film prepared by EM (Composite-E) compared to that for the all-cellulose nanocomposite film prepared by AM (Composite-A). Composite-E also showed a better optical transparency than Composite-A. The thermal stability of the two RWSCs presented contrary results when the CNFs were added, indicating a higher thermal stability for Composite-E than for Composite-A. This should have determined the properties of the films in which Cellulose I and Cellulose II coexisted for the all-cellulose nanocomposite films, and the forming mechanism of Cellulose II and crystallinity were determined by the cellulose-extracting method. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy also showed that there was more Cellulose I in Composite-E than in Composite-A. The results are expected to enrich the data for deep processing of agricultural residues.

Enhanced Antimicrobial Cellulose/Chitosan/ZnO Biodegradable Composite Membrane

In this study, chitosan and sugarcane cellulose were used as film-forming materials, while the inorganic agent zinc oxide (ZnO) and natural compound phenyllactic acid (PA) were used as the main bacteriostatic components to fabricate biodegradable antimicrobial composite membranes. The water absorption and antimicrobial properties were investigated by adjusting the concentration of PA. The scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results demonstrated that the components of the composite membrane were successfully integrated. The addition of ZnO improved the mechanical and antimicrobial properties of the composite membrane, while the addition of PA with high crystallinity significantly reduced the water absorption and swelling. Moreover, the addition of 0.5% PA greatly improved the water absorption of the composite membrane. The results of antimicrobial experiments showed that PA improved the antimicrobial activity of the composite membrane against Staphylococcus aureus, Escherichia coli, Aspergillus niger and Penicillium rubens. Among them, 0.3% PA had the best antimicrobial effect against S. aureus, E. coli and A. niger, while 0.7% PA had the best antimicrobial effect against P. rubens.

Utilization of Cellulose to Its Full Potential: A Review on Cellulose Dissolution, Regeneration, and Applications

As the most abundant natural polymer, cellulose is a prime candidate for the preparation of both sustainable and economically viable polymeric products hitherto predominantly produced from oil-based synthetic polymers. However, the utilization of cellulose to its full potential is constrained by its recalcitrance to chemical processing. Both fundamental and applied aspects of cellulose dissolution remain active areas of research and include mechanistic studies on solvent-cellulose interactions, the development of novel solvents and/or solvent systems, the optimization of dissolution conditions, and the preparation of various cellulose-based materials. In this review, we build on existing knowledge on cellulose dissolution, including the structural characteristics of the polymer that are important for dissolution (molecular weight, crystallinity, and effect of hydrophobic interactions), and evaluate widely used non-derivatizing solvents (sodium hydroxide (NaOH)-based systems, N,N-dimethylacetamide (DMAc)/lithium chloride (LiCl), N-methylmorpholine-N-oxide (NMMO), and ionic liquids). We also cover the subsequent regeneration of cellulose solutions from these solvents into various architectures (fibers, films, membranes, beads, aerogels, and hydrogels) and review uses of these materials in specific applications, such as biomedical, sorption, and energy uses.

Current Opportunities and Challenges in Biopolymer Thin Film Analysis—Determination of Film Thickness

Polymer thin films with thickness below 100 nm are a fascinating class of 2D materials with commercial and research applications in many branches ranging from coatings to photoresists and insulating materials, to mention just a few uses. Biopolymers have extended the scope of polymer thin films with unique materials such as cellulose, cellulose nanocrystals, cellulose nanofibrils with tunable water uptake, crystallinity and optical properties. The key information needed in thin biopolymer film use and research is film thickness. It is often challenging to determine precisely and hence several techniques and their combinations are used. Additional challenges with hydrophilic biopolymers such as cellulose are the presence of humidity and the soft and often heterogenous structure of the films. This minireview summarizes currently used methods and techniques for biopolymer thin film thickness analysis and outlines challenges for accurate and reproducible characterization. Cellulose is chosen as the representative biopolymer.

Non-productive binding of cellobiohydrolase i investigated by surface plasmon resonance spectroscopy

Future biorefineries are facing the challenge to separate and depolymerize biopolymers into their building blocks for the production of biofuels and basic molecules as chemical stock. Fungi have evolved lignocellulolytic enzymes to perform this task specifically and efficiently, but a detailed understanding of their heterogeneous reactions is a prerequisite for the optimization of large-scale enzymatic biomass degradation. Here, we investigate the binding of cellulolytic enzymes onto biopolymers by surface plasmon resonance (SPR) spectroscopy for the fast and precise characterization of enzyme adsorption processes. Using different sensor architectures, SPR probes modified with regenerated cellulose as well as with lignin films were prepared by spin-coating techniques. The modified SPR probes were analyzed by atomic force microscopy and static contact angle measurements to determine physical and surface molecular properties. SPR spectroscopy was used to study the activity and affinity of Trichoderma reesei cellobiohydrolase I (CBHI) glycoforms on the modified SPR probes. N-glycan removal led to no significant change in activity or cellulose binding, while a slightly higher tendency for non-productive binding to SPR probes modified with different lignin fractions was observed. The results suggest that the main role of the N-glycosylation in CBHI is not to prevent non-productive binding to lignin, but probably to increase its stability against proteolytic degradation. The work also demonstrates the suitability of SPR-based techniques for the characterization of the binding of lignocellulolytic enzymes to biomass-derived polymers.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10570-021-04002-6.

Biodegradation of Functionalized Nanocellulose

Nanocellulose has attracted widespread interest for applications in materials science and biomedical engineering due to its natural abundance, desirable physicochemical properties, and high intrinsic mineralizability (i.e., complete biodegradability). A common strategy to increase dispersibility in polymer matrices is to modify the hydroxyl groups on nanocellulose through covalent functionalization, but such modification strategies may affect the desirable biodegradation properties exhibited by pristine nanocellulose. In this study, cellulose nanofibrils (CNFs) functionalized with a range of esters, carboxylic acids, or ethers exhibited decreased rates and extents of mineralization by anaerobic and aerobic microbial communities compared to unmodified CNFs, with etherified CNFs exhibiting the highest level of recalcitrance. The decreased biodegradability of functionalized CNFs depended primarily on the degree of substitution at the surface of the material rather than within the bulk. This dependence on surface chemistry was attributed not only to the large surface area-to-volume ratio of nanocellulose but also to the prerequisite surface interaction by microorganisms necessary to achieve biodegradation. Results from this study highlight the need to quantify the type and coverage of surface substituents in order to anticipate their effects on the environmental persistence of functionalized nanocellulose.

Benchmarking Cellulose Nanocrystals Part II: New Industrially Produced Materials

The demand for industrially produced cellulose nanocrystals (CNCs) has been growing since 2012, when CelluForce Inc. opened its inaugural demonstration plant with a production capacity of 1 tonne per day. Currently, there are 10 industrial CNC producers worldwide, each producing a unique material. Thus, academic researchers and commercial users alike must consider the properties of all available CNCs and carefully select the material which will optimize the performance of their desired application. To support these efforts, this article presents a thorough characterization of four new industrially produced CNCs including sulfated CNCs from NORAM Engineering and Constructors Ltd. (in cooperation with InnoTech Alberta and Alberta-Pacific Forest Industries Inc.) and Melodea Ltd., as well as carboxylated CNCs from Anomera Inc. and Blue Goose Biorefineries Inc. These materials were benchmarked against typical lab-made, sulfated CNCs. While all CNCs were similar in size, shape, crystallinity, and suspension quality, the sulfated CNCs had a higher surface charge density than their carboxylated counterparts, leading to higher colloidal stability. Additionally, significant differences in the rheological profiles of aqueous CNC suspensions, as well as CNC thermal stability and self-assembly behavior, were observed. As such, this article highlights both the subtle and significant differences between five CNC types and acts as a guide for end-users looking to optimize the performance of CNC-based materials.

Cellulose Nanomaterials in Interfacial Evaporators for Desalination: A "Natural" Choice

Herein, the recent advances in realizing highly efficient cellulose-based solar evaporators for alleviating the global water crisis are summarized. Fresh water scarcity is one of the most threatening issues for sustainable development. Solar steam generation, which harnesses the abundant sunlight, has been recognized as a sustainable approach to harvest fresh water. In contrast to synthetic polymeric materials that can pose serious negative environmental impacts, cellulose-based materials, owing to their biocompatibility, renewability, and sustainability, are highly attractive for realizing solar steam generators. The molecular and macromolecular features of cellulose and the physicochemical properties of extracted cellulose nanoparticles (cellulose nanocrystals and cellulose nanofibrils (CNF)) and natural cellulose materials (wood and bacterial nanocellulose (BNC)) that make them attractive as supporting substrate materials in solar steam generators are briefly discussed. Recent progress in designing highly efficient cellulose-based solar evaporators, including utilizing extracted cellulose nanoparticles via bottom-up assembly CNF, natural cellulose materials with intrinsic hierarchical structure (wood and BNC), and commercial planar cellulose substrates (air-laid paper, cellulose paper, and cotton fabric) is reviewed. The outstanding challenges that need to be addressed for these materials and devices to be utilized in the real-world and in overcoming global water crisis are also briefly highlighted.

Functional Materials from Nanocellulose: Utilizing Structure-Property Relationships in Bottom-Up Fabrication

It is inherently challenging to recapitulate the precise hierarchical architectures found throughout nature (such as in wood, antler, bone, and silk) using synthetic bottom-up fabrication strategies. However, as a renewable and naturally sourced nanoscale building block, nanocellulose-both cellulose nanocrystals and cellulose nanofibrils-has gained significant research interest within this area. Altogether, the intrinsic shape anisotropy, surface charge/chemistry, and mechanical/rheological properties are some of the critical material properties leading to advanced structure-based functionality within nanocellulose-based bottom-up fabricated materials. Herein, the organization of nanocellulose into biomimetic-aligned, porous, and fibrous materials through a variety of fabrication techniques is presented. Moreover, sophisticated material structuring arising from both the alignment of nanocellulose and via specific process-induced methods is covered. In particular, design rules based on the underlying fundamental properties of nanocellulose are established and discussed as related to their influence on material assembly and resulting structure/function. Finally, key advancements and critical challenges within the field are highlighted, paving the way for the fabrication of truly advanced materials from nanocellulose.

The use of model cellulose gel beads to clarify flame-retardant characteristics of layer-by-layer nanocoatings

Layer-by-Layer (LbL) assembled nanocoatings are exploited to impart flame-retardant properties to cellulosic substrates. A model cellulose material can make it possible to investigate an optimal bilayer (BL) range for the deposition of coating while elucidating the main flame-retardant action thus allowing for an efficient design of optimized LbL formulations. Model cellulose gel beads were prepared by dissolving cellulose-rich fibers followed by precipitation. The beads were LbL-treated with chitosan (CH) and sodium hexametaphosphate (SHMP). The char forming properties were studied using thermal gravimetric analysis. The coating increased the char yield in nitrogen to up to 29 % and showed a distinct pattern of micro intumescent behavior upon heating. An optimal range of 10-20 BL is observed. The well-defined model cellulose gel beads hence introduce a new scientific route both to clarify the fundamental effects of different film components and to optimize the composition of the films.

Real-time adsorption of optical brightening agents on cellulose thin films

Optical brightening agents (OBAs) are commonly used in textile and paper industry to adjust product brightness and color appearence. Continuous production processes lead to short residence time of the dyes in the fiber suspension, making it necessary to understand the kinetics of adsorption. The interaction mechanisms of OBAs with cellulose are challenging to establish as the fibrous nature of cellulosic substrates complicates acquisition of real-time data. Here, we explore the real-time adsorption of different OBAs (di, tetra- and hexasulfonated compounds) onto different cellulose surfaces using surface plasmon resonance spectroscopy. Ionic strength, surface topography and polarity were varied and yielded 0.76-11.35 mg m^-2 OBA on cellulose. We identified four independent mechanisms governing OBA-cellulose interactions. These involve the polarity of the cellulose surface, the solubility of the OBA, the ionic strength during adsorption and presence of bivalent cations such as Ca²⁺. These results can be exploited for process optimization in related industries as they allow for a simple adjustment and experimental testing procedures including performance assessment of novel OBAs.

Model Surfaces for Paper Fibers Prepared from Carboxymethyl Cellulose and Polycations

For tailored functionalization of cellulose based papers, the interaction between paper fibers and functional additives must be understood. Planar cellulose surfaces represent a suitable model system for studying the binding of additives. In this work, polyelectrolyte multilayers (PEMs) are prepared by alternating dip-coating of the negatively charged cellulose derivate carboxymethyl cellulose and a polycation, either polydiallyldimethylammonium chloride (PDADMAC) or chitosan (CHI). The parameters varied during PEM formation are the concentrations (0.1-5 g/L) and pH (pH = 2-6) of the dipping solutions. Both PEM systems grow exponentially, revealing a high mobility of the polyelectrolytes (PEs). The pH-tunable charge density leads to PEMs with different surface topographies. Quartz crystal microbalance experiments with dissipation monitoring (QCM-D) reveal the pronounced viscoelastic properties of the PEMs. Ellipsometry and atomic force microscopy (AFM) measurements show that the strong and highly charged polycation PDADMAC leads to the formation of smooth PEMs. The weak polycation CHI forms cellulose model surfaces with higher film thicknesses and a tunable roughness. Both PEM systems exhibit a high water uptake when exposed to a humid environment, with the PDADMAC/carboxymethyl cellulose (CMC) PEMs resulting in a water uptake up to 60% and CHI/CMC up to 20%. The resulting PEMs are water-stable, but water swellable model surfaces with a controllable roughness and topography.

Water Content of Polyelectrolyte Multilayer Films Measured by Quartz Crystal Microbalance and Deuterium Oxide Exchange

Water content of natural and synthetic, thin, polymer films is of considerable interest to a variety of fields because it governs properties such as ion conductivity, rigidity, porosity, and mechanical strength. Measuring thin film water content typically requires either complicated and expensive instrumentation or use of multiple instrumental techniques. However, because a quartz crystal microbalance (QCM) is sensitive to changes in mass and viscosity, deuterated solvent exchange has emerged as a simple, single-instrument, in situ method to quantify thin film water content. Relatively few studies, though, have employed this technique to measure water content of polyelectrolyte multilayers formed by layer-by-layer (LbL) assembly. In this work, poly (allyl amine) (PAH) and poly (styrene sulfonate) (PSS) films of up to nine layers were formed and the water content for each layer was measured via QCM with deuterium oxide exchange. The well-characterized nature of PAH/PSS films facilitated comparisons of the technique used in this work to other instrumental methods. Water content results showed good agreement with the literature and good precision for hydrated films thicker than 20 nm. Collectively, this work highlights the utility, repeatability, and limitations of this deuterated exchange technique in measuring the solvent content of thin films.

Design strategies, properties and applications of cellulose nanomaterials-enhanced products with residual, technical or nanoscale lignin-A review

With the increasing demand for greener alternatives to fossil-derived products, research on cellulose nanomaterials (CNMs) has rapidly expanded. The combination of nanoscale properties and sustainable attributes makes CNMs an asset in the quest for a sustainable society. However, challenges such as the hydrophilic nature of CNMs, their low compatibility with non-polar matrices and modest thermal stability, slow the development of end-uses. Combination of CNMs with amphiphilic lignin can improve the thermal stability, enhance the compatibility with non-polar matrices and, additionally, endow CNMs with new functionalities e.g., UV shielding or antioxidative properties. This article comprehensively reviews the different design strategies and their influence on properties and applications of CNMs containing lignin in various forms; either as residual lignin, added technical lignin, or nanoscale particles. The review focuses especially on the synergy created between CNMs and lignin, paving the way for new production routes and use of CNM/lignin materials in high-performance applications.

From Cellulose to Cellulose Nanofibrils-A Comprehensive Review of the Preparation and Modification of Cellulose Nanofibrils

This review summarizes the preparation methods of cellulose nanofibrils (CNFs) and the progress in the research pertaining to their surface modification. Moreover, the preparation and surface modification of nanocellulose were comprehensively introduced based on the existing literature. The review focuses on the mechanical treatment of cellulose, the surface modification of fibrillated fibers during pretreatment, the surface modification of nanocellulose and the modification of CNFs and their functional application. In the past five years, research on cellulose nanofibrils has progressed with developments in nanomaterials research technology. The number of papers on nanocellulose alone has increased by six times. However, owing to its high energy consumption, high cost and challenging industrial production, the applications of nanocellulose remain limited. In addition, although nanofibrils exhibit strong biocompatibility and barrier and mechanical properties, their high hydrophilicity limits their practical application. Current research on cellulose nanofibrils has mainly focused on the industrial production of CNFs, their pretreatment and functional modification and their compatibility with other biomass materials. In the future, with the rapid development of modern science and technology, the demand for biodegradable biomass materials will continue to increase. Furthermore, research on bio-based nanomaterials is expected to advance in the direction of functionalization and popularization.

Fabrication of all-cellulose nanocomposites from corn stalk

BACKGROUND

There is a need to help farmers and industries develop value-added composite and nanocomposite materials from agricultural residuals. Cellulose nanofibers (CNFs) were made using a TEMPO oxidation method and celluloses were prepared by acid-base method and extracting method, which were all from corn stalk, an agricultural residual. The prepared celluloses were dissolved separately in dimethylacetamide/LiCl solvent and CNFs were added at 0.0%, 0.5%, 1.5% and 3.0% to form all-cellulose nanocomposites, and then cast into films. Morphology, structure and properties of the nanocomposite films were characterized using atomic force microscopy, field emission scanning electron microscopy, thermogravimetric analysis, X-ray diffraction and mechanical testing.

RESULTS

The all-cellulose nanocomposite films with different cellulose matrices exhibited good optical transparency and layer structure. The all-cellulose nanocomposite films with cellulose prepared by the extracting method (Composite E) exhibited a higher crystallinity, better thermal stability and higher mechanical strength compared to the all-cellulose nanocomposite films with cellulose prepared by the acid-base method (Composite A).

CONCLUSIONS

The crystal structure of the all-cellulose nanocomposite films indicated the coexistence of cellulose I and cellulose II. However, in contrast to Composite A, the diffraction intensity of cellulose I in Composite E was higher than that of cellulose II. This was another reason that the mechanical properties of Composite E were superior to those of Composite A. In addition, the mechanical properties of the all-cellulose nanocomposite films were significantly different when the addition of CNFs reached 3.0% by weight, as indicated by a multiple-range comparison. © 2020 Society of Chemical Industry.

Patience is a virtue: self-assembly and physico-chemical properties of cellulose nanocrystal allomorphs

Cellulose nanocrystals (CNCs) are bio-based rod-like nanoparticles with a quickly expanding market. Despite the fact that a variety of production routes and starting cellulose sources are employed, all industrially produced CNCs consist of cellulose I (CNC-I), the native crystalline allomorph of cellulose. Here a comparative study of the physico-chemical properties and liquid crystalline behavior of CNCs produced from cellulose II (CNC-II) and typical CNC-I is reported. CNC-I and CNC-II are isolated by sulfuric acid hydrolysis of cotton and mercerized cotton, respectively. The two allomorphs display similar surface charge densities and ζ-potentials and both have a right-handed twist, but CNC-II have a slightly smaller average length and aspect ratio, and are less hygroscopic. Interestingly, the self-assembly behavior of CNC-I and CNC-II in water is different. Whilst CNC-I forms a chiral nematic phase, CNC-II initially phase separates into an upper isotropic and a lower nematic liquid crystalline phase, before a slow reorganization into a large-pitch chiral nematic texture occurs. This is potentially caused by a combination of factors, including the inferred faster rotational diffusion of CNC-II and the different crystal structures of CNC-I and CNC-II, which are responsible for the presence and absence of a giant dipole moment, respectively.

On the interaction of softwood hemicellulose with cellulose surfaces in relation to molecular structure and physicochemical properties of hemicellulose

The substantial part of the water-soluble hemicellulose fraction, obtained when processing cellulose to produce paper and other products, has so far been discarded. The aim of this work is to reveal the interfacial properties of softwood hemicellulose (galactoglucomannan, GGM) in relation to their molecular and solution structure. In this study the sugar composition of GGM was characterised by chemical analysis as well as 1D and 2D NMR spectroscopy. Previously it has been demonstrated that hemicellulose has high affinity towards cellulose and has the ability to alter the properties of cellulose based products. This study is focused on the interactions between hemicellulose and the cellulose surface. Therefore, adsorption to hydrophobized silica and cellulose surfaces of two softwood hemicellulose samples and structurally similar seed hemicelluloses (galactomannans, GMs) was studied with ellipsometry, QCM-D and neutron reflectometry. Aqueous solutions of all samples were characterized with light scattering to determine how the degree of side-group substitution and molecular weight affect the conformation and aggregation of these polymers in the bulk. In addition, hemicellulose samples were studied with SAXS to investigate backbone flexibility. Light scattering results indicated that GM polymers form globular particles while GGMs were found to form rod-like aggregates in the solution. The polysaccharides exhibit higher adsorption to cellulose than on hydrophobic surfaces. A clear correlation between the increase in molecular weight of polysaccharides and increasing adsorbed amount on cellulose was observed, while the adsorbed amount on the hydrophobic surface was fairly independent of the molecular weight. The obtained layer thickness was compared with bulk scattering data and the results indicated flat conformation of the polysaccharides on the surface.

Effect of Rhodococcus sp. pretreatment on cellulose hydrolysis of corn stalk

Pretreatment can improve the hydrolysis efficiency of cellulose, in which biological pretreatment plays an important role. In the present study, we uncovered that Rhodococcus has the ability of lignin degradation, which can decompose lignin and serve as a carbon source to meet the needs of its own growth. We used Rhodococcus to pretreat the corn stalks and evaluate the effect on cellulose hydrolysis. The concentration of reducing sugar produced by the hydrolysis of corn stalk after pretreatment of Rhodococcus is 2.95 g/L. SEM imaging showed that Rhodococcus pretreatment resulted the surface of corn stalk to be no longer complete, some lamellar structures fall off, and leave obvious traces, and obvious delamination was found at the edge of the fault. AFM imaging showed that the pretreatment changed the lignin structure of the corn stalk material surface, resulting in a higher surface roughness of 9.37. These results indicated that Rhodococcus pretreatment can improve the saccharification efficiency of cellulose by removing lignin and increasing the surface roughness of the material.

Adhesion and Stability of Nanocellulose Coatings on Flat Polymer Films and Textiles

Renewable nanocellulose materials received increased attention owing to their small dimensions, high specific surface area, high mechanical characteristics, biocompatibility, and compostability. Nanocellulose coatings are among many interesting applications of these materials to functionalize different by composition and structure surfaces, including plastics, polymer coatings, and textiles with broader applications from food packaging to smart textiles. Variations in porosity and thickness of nanocellulose coatings are used to adjust a load of functional molecules and particles into the coatings, their permeability, and filtration properties. Mechanical stability of nanocellulose coatings in a wet and dry state are critical characteristics for many applications. In this work, nanofibrillated and nanocrystalline cellulose coatings deposited on the surface of polymer films and textiles made of cellulose, polyester, and nylon are studied using atomic force microscopy, ellipsometry, and T-peel adhesion tests. Methods to improve coatings’ adhesion and stability using physical and chemical cross-linking with added polymers and polycarboxylic acids are analyzed in this study. The paper reports on the effect of the substrate structure and ability of nanocellulose particles to intercalate into the substrate on the coating adhesion.

Adsorption of xyloglucan and cellulose nanocrystals on natural fibres for the creation of hierarchically structured fibres

Green treatment of natural fibres is a major issue in paper, textile and biocomposites industries to design innovative and eco-friendly products. In this work, hierarchical structuring of flax woven fabrics by the adsorption of xyloglucan (XG) and cellulose nanocrystals (CNC) is studied. Indeed, CNC have high mechanical properties, high specific surface area and great potential for functionalization. The adsorption of XG and CNC has been investigated in terms of localization by confocal and scanning electron microscopy (SEM) and quantification through adsorption isotherms. Adhesion force measurements have also been performed by Atomic Force Microscopy (AFM). XG and CNC are homogeneously adsorbed on flax fabric and adsorption isotherms reach plateau values around 20 mg /g_fibres for both. The pre-adsorption of XG on flax fabric influences the amount of adsorbed CNC in the high concentrations and also creates entanglements and strong interactions between XG and CNC with the formation of an extensible network.

Bottom-up assembly of nanocellulose structures

Nanocelluloses, both cellulose nanofibrils and cellulose nanocrystals, are gaining research traction due to their viability as key components in commercial applications and industrial processes. Significant efforts have been made to understand both the potential of assembling nanocelluloses, and the limits and prospectives of the resulting structures. This Review focuses on bottom-up techniques used to prepare nanocellulose-only structures, and details the intermolecular and surface forces driving their assembly. Additionally, the interactions that contribute to their structural integrity are discussed along with alternate pathways and suggestions for improved properties. Six categories of nanocellulose structures are presented: (1) powders, beads, and droplets; (2) capsules; (3) continuous fibres; (4) films; (5) hydrogels; and (6) aerogels and dried foams. Although research on nanocellulose assembly often focuses on fundamental science, this Review also provides insight on the potential utilization of such structures in a wide array of applications.

Cellulose from sources to nanocellulose and an overview of synthesis and properties of nanocellulose/zinc oxide nanocomposite materials

Recently, environmental and ecological concerns are increasing due to the usage of petroleum-based products so the synthesis of ultra-fine chemicals and functional materials from natural resources is drawing a tremendous level of attention. Nanocellulose, a unique and promising natural material extracted from native cellulose, may prove to be most ecofriendly materials that are technically and economically feasible in modern times, minimizing the pollution generation. Nanocellulose has gained tremendous attention for its use in various applications, due to its excellent special surface chemistry, physical properties, and remarkable biological properties (biodegradability, biocompatibility, and non-toxicity). Various types of nanocellulose, viz. cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial nanocellulose (BNC), are deeply introduced and compared in this work in terms of sources, production, structures and properties. The metal and metal oxides especially zinc oxide nanoparticles (ZnO-NPs) are broadly used in various fields due to the diversity of functional properties such as antimicrobial and ultraviolet (UV) properties. Thus, the advancement of nanocellulose and zinc oxide nanoparticles (ZnO-NPs)-based composites materials are summarized in this article in terms of the preparation methods and remarkable properties with the help of recent knowledge and significant findings (especially from the past six years reports). The nanocellulose materials complement zinc oxide nanoparticles, where they impart their functional properties to the nanoparticle composites. As a result hybrid nanocomposite containing nanocellulose/zinc oxide composite has shown excellent mechanical, UV barrier, and antibacterial properties. The nanocellulose based hybrid nanomaterials have huge potential applications in the area of food packaging, biopharmaceuticals, biomedical, and cosmetics. Thus the functional composite materials containing nanocellulose and zinc oxide will determine the potential biomedical application for nanocellulose.

Deposition of Cellulose Nanocrystals onto Supported Lipid Membranes

The deposition of cellulose nanocrystals (CNCs) on a supported lipid bilayer (SLB) was investigated at different length scales. Quartz crystal microbalance with dissipation monitoring (QCM-D) was used to probe the bilayer formation and to show for the first time the CNC deposition onto the SLB. Specifically, classical QCM-D measurements gave estimation of the adsorbed hydrated mass and the corresponding film thickness, whereas complementary experiments using D₂O as the solvent allowed the quantitative determination of the hydration of the CNC layer, showing a high hydration value. Scanning force microscopy (SFM) and total internal reflection fluorescence microscopy (TIRF) were used to probe the homogeneity of the deposited layers, revealing the structural details at the particle and film length scales, respectively, thus giving information on the effect of CNC concentration on the surface coverage. The results showed that the adsorption of CNCs on the supported lipid membrane depended on lipid composition, CNC concentration, and pH conditions, and that the binding process was governed by electrostatic interactions. Under suitable conditions, a uniform film was formed, with thickness corresponding to a CNC monolayer, which provides the basis for a relevant 2D model of a primary plant cell wall.

Waste paper: An underutilized but promising source for nanocellulose mining

Nanocellulose has achieved an inimitable place and value in nano-materials research sector. Promising and exclusive physical, chemical and biological properties of nanocellulose make it an attractive and ideal material for various high end-user applications. Conventionally, the base material for nanocellulose i.e. cellulose is being extracted from various lignocellulosic raw materials (like wood, agro-industrial-residues, etc.) using pulping followed by bleaching sequences. As an alternate to lignocellulosic raw materials, waste paper also showed potential as a competent raw material due to its abundant availability and high cellulosic content (60-70%) with comparatively less hemicelluloses (10-20%) and lignin (5-10%) without any harsh treatments. The production yields of nanocellulose were reported to vary from 1.5% to 64% depending upon the waste papers and treatments given. The diameters of these nanocelluloses were reported in the range of 2-100 nm and crystallinity range around 54-95%. Thermal degradation of waste paper nanocellulose was varied from 187 °C to 371 °C. Although these properties are comparable with the nanocellulose obtained from lignocellulosic raw materials, yet waste paper is an underutilized source for nanocellulose preparation due to its ordinary fate of recycling, dumping and incineration. In the sight of necessity and possibility of waste paper utilization, this article reviews the outcomes of research carried out for preparation of nanocellulose using waste paper as a source of cellulose. There is a need of sincere investigation to convert this valuable waste to wealth i.e. waste papers to nanocellulose, which will be helpful in solid waste management to protect environment in economical way.