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Cellulose cryogels are promising eco-friendly materials that exhibit low density, high porosity, and renewability. However, the applications of these materials are limited by their lower mechanical and water resistance compared to petrochemical-based lightweight materials. In this work, nanocelluloses were functionalized with cationic and anionic groups, and these nanomaterials were combined to obtain strong and water-resilient cryogels. To prepare the cryogels, anionic and cationic micro- and nanofibrils (CNFs) were produced at three different sizes and combined in various weight ratios, forming electrostatic complexes. The complex phase was concentrated by centrifugation and freeze-dried. Porous and open cellular structures were assembled in all compositions tested (porosity >90 %). Compressive testing revealed that the most resistant cryogels (1.7 MPa) were obtained with equivalent amounts of negatively and positively charged CNFs with lengths between 100 and 1200 nm. The strength at this condition was achieved as CNF electrostatic complexes assembled in thick cells, as observed by synchrotron X-ray tomography. In addition to mechanical strength, electrostatic complexation provided remarkable structural stability in water for the CNF cryogels, without compromising their biodegradability. This route by electrostatic complexation is a practical strategy to combine and concentrate nanocelluloses to tailor biodegradable lightweight materials with high strength and wet stability.

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The development of flexible and porous materials to control antibacterial delivery is a pivotal endeavor in medical science. In this study, we aimed to produce long and defect-free fibers made of zein and hydroxypropyl methylcellulose acetate succinate (HPMCAS) to be used as a platform for the release of metronidazole (MDZ) and metronidazole benzoate (BMDZ) to be potentially used in periodontal treatment. Microfibers prepared via electrospinning under a 2:3 (w/w) zein to HPMCAS ratio, containing 0.5 % (w/w) poly(ethylene oxide) (PEO) and 1 % (w/w) cellulose nanofibril (CNF) were loaded with 40 % (w/w) MDZ, 40 % (w/w) BMDZ, or a combination of 20 % (w/w) of each drug. The addition of CNF improved the electrospinning process, resulting in long fibers with reduced MDZ and BMDZ surface crystallization. MDZ- and BMDZ-incorporated fibers were semicrystalline and displayed commendable compatibility among drugs, nanocellulose and polymeric chains. Release tests showed that zein/HPMCAS/PEO fibers without CNF and with 20 % (w/w) MDZ/ 20 % (w/w) BMDZ released the drug at a slower and more sustained rate compared to other samples over extended periods (up to 5 days), which is a favorable aspect concerning periodontitis treatment.

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Cellulose nanomaterials (CNs) are promising green materials due to their unique properties as well as their environmental benefits. Among these materials, cellulose nanofibrils (CNFs) and nanocrystals (CNCs) are the most extensively researched types of CNs. While they share some fundamental properties like low density, biodegradability, biocompatibility, and low toxicity, they also possess unique differentiating characteristics such as morphology, rheology, aspect ratio, crystallinity, mechanical and optical properties. Therefore, numerous comparative studies have been conducted, and recently, various studies have reported the synergetic advantages resulting from combining CNF and CNC. In this review, we initiate by addressing the terminology used to describe combinations of these and other types of CNs, proposing "hybrid cellulose nanomaterials" (HCNs) as the standardized classifictation for these materials. Subsequently, we briefly cover aspects of properties-driven applications and the performance of CNs, from both an individual and comparative perspective. Next, we comprehensively examine the potential of HCN-based materials, highlighting their performance for various applications. In conclusion, HCNs have demonstraded remarkable success in diverse areas, such as food packaging, electronic devices, 3D printing, biomedical and other fields, resulting in materials with superior performance when compared to neat CNF or CNC. Therefore, HCNs exhibit great potential for the development of environmentally friendly materials with enhanced properties.

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We review the recent progress that have led to the development of porous materials based on cellulose nanostructures found in plants and other resources. In light of the properties that emerge from the chemistry, shape and structural control, we discuss some of the most promising uses of a plant-based material, nanocellulose, in regenerative medicine. Following a brief discussion about the fundamental aspects of self-assembly of nanocellulose precursors, we review the key strategies needed for material synthesis and to adjust the architecture of the materials (using three-dimensional printing, freeze-casted porous materials, and electrospinning) according to their uses in tissue engineering, artificial organs, controlled drug delivery and wound healing systems, among others. For this purpose, we map the structure-property-function relationships of nanocellulose-based porous materials and examine the course of actions that are required to translate innovation from the laboratory to industry. Such efforts require attention to regulatory aspects and market pull. Finally, the key challenges and opportunities in this nascent field are critically reviewed.

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Cellulose nanofibrils (CNFs) have emerged as a potential alternative to synthetic polymers in packaging applications owing to their oxygen and grease barrier performance, as well as their strong mechanical properties. However, the performance of CNF films relies on the inherent characteristics of fibers, which undergo changes during the CNF isolation process. Understanding these variations in characteristics during CNF isolation is crucial for tailoring CNF film properties to achieve optimum performance in packaging applications. In this study, CNFs were isolated by endoglucanase-assisted mechanical ultra-refining. The alterations in the intrinsic characteristics of CNFs and their impact on CNF films were systematically investigated by considering the degree of defibrillation, enzyme loading, and reaction time through a design of experiments. Enzyme loading had a significant influence on the crystallinity index, crystallite size, surface area, and viscosity. Meanwhile, the degree of defibrillation greatly affected the aspect ratio, degree of polymerization, and particle size. CNF films prepared from CNFs isolated under two optimized scenarios (casting and coating applications) exhibited remarkable properties, including high thermal stability (approximately 300 °C), high tensile strength (104 - 113 MPa), excellent oil resistance (kit n°12), and low oxygen transmission rate (1.00 - 3.17 cc·m-2.day-1). Therefore, endoglucanase pretreatment can aid in obtaining CNFs with lower energy consumption, resulting in films that possess higher transmittance, superior barrier performance, and reduced surface wettability compared to control samples without enzymatic pretreatment and other unmodified CNF films reported in the literature, all while maintaining mechanical and thermal performance without significant loss.

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Rheological parameters of cellulose nanofibril dispersions (CNF) are relevant and commonly used as quality control for producing of this type of material. These parameters are affected by morphological features and size distribution of the nanofibrils. Understanding the effect of size distribution is essential for analyzing the rheological properties, viscosity control, performance of CNFs, and potential dispersion applications. This study aims at comprehending how the morphological characteristics of the CNFs and their size distribution affect the rheological behavior of dispersions. The CNF dispersions were fractionated by size, obtaining six fractions of each, which were analyzed for their morphology and rheology (viscosity, intrinsic viscosity). In the dilute region, the viscosity and intrinsic viscosity behavior of CNF dispersions are linear concerning the size distribution present in the dispersion. In the semi-dilute region, the size of the fibrils and the fiber aggregates have a relevant effect on the viscosity behavior of CNF dispersions, which are satisfactorily related (R2 = 0.997) using the rule of logarithmic additivity of the dispersion viscosities of size fractions.

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Chemical modification in surface of cellulose nanofibrils CNFs (20 nm) from an endemic and non-significant value-added, Argentine bamboo, was developed. The modification in the CNFs was carried out with three simple routes using a low molecular weight polylactic acid synthesized in our laboratory (PLA1). The first step comprises of protection of the hydroxyl groups of PLA1 through a benzoylation (PLA1Bz). The next step consisted of the activation of carboxyl groups using thionyl chloride and the last reaction was the grafting of the modified PLA onto the CNFs (PLA1Bz-g-CNF). The covalently functionalization is confirmed by spectroscopically techniques as well as PLA1Bz-g-CNFs were characterized by thermal analyses. The PLA1Bz-g-CNFs were taken up such as nanocharges to improve properties of compatibilization and changing surface properties in films based on PLA. The comparison between the films with PLA1Bz-g-CNFs with respect to the physic mixture of the components (PLA1Bz/CNF), shows an improvement in the thermal, mechanical, and surface properties of the material, particularly when 5% of PLA1Bz-g-CNFs was added. The dispersive (γS D) component of film is increased in 36.1 mN/m respect to 29.3 mN/m from the films obtained with the physic mixture nanofibrils without modification and a plasticizing effect was noticed in the final material.

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Mineral fillers hinder cellulosic fiber bonding and thus limit the increase of filler content in paper. Herein, precipitated calcium carbonate (PCC)/cellulose nanofibrils (CNF) composites were fabricated by a facile and efficient strategy, i.e., co-refining process (CRP). During this process, CNF and PCC were activated by mechanochemical effect and formed encapsulation structure by calcium ion coordination and hydrogen bonding. The encapsulation structure and H-bond/ionic coordination interactions not only endowed the composite with excellent size stability but also enhanced interfacial interaction between composite fillers and cellulosic fibers. Compare with the paper filled with only PCC, PCC + CNF mixture, the tensile index of the cellulosic paper containing PCC/CNF composite was increased by 44.48% and 12.14%, respectively. These results not only provide a facile and scalable approach to increase interaction between cellulosic fiber and mineral filler but also create more possibilities for special paper-based materials with requiring high content of inorganic materials.

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The growing demand for products with lower environmental impact and the extensive applicability of cellulose nanofibrils (CNFs) have received attention due to their attractive properties. In this study, bio-based films/nanopapers were produced with CNFs from banana tree pseudostem (BTPT) wastes and Eucalyptus kraft cellulose (EKC) and were evaluated by their properties, such as mechanical strength, biodegradability, and light transmittance. The CNFs were produced by mechanical fibrillation (after 20 and 40 passages) from suspensions of BTPT (alkaline pre-treated) and EKC. Films/nanopapers were produced by casting from both suspensions with concentrations of 2% (based in dry mass of CNF). The BTPT films/nanopapers showed greater mechanical properties, with Young's modulus and tensile strength around 2.42 GPa and 51 MPa (after 40 passages), respectively. On the other hand, the EKC samples showed lower disintegration in water after 24 h and biodegradability. The increase in the number of fibrillation cycles produced more transparent films/nanopapers and caused a significant reduction of water absorption for both raw materials. The permeability was similar for the films/nanopapers from BTPT and EKC. This study indicated that attractive mechanical properties and biodegradability, besides low cost, could be achieved by bio-based nanomaterials, with potential for being applied as emulsifying agents and special membranes, enabling more efficient utilization of agricultural wastes.

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During the last two decades cellulosic nanomaterials have been the subject of much research around the world. Moreover, in the last few years, increasing industrial interest on the field enabled the setting-up of the first facilities producing commercial quantities of nanocelluloses; whereas a number of inventions involving cellulose nano-objects are claimed every year. In this context, the current article describes the recent evolution (from 2010 till 2017) of published patents which explicitly include in their title, abstract and/or claims references to cellulose nano-objects such as cellulose nanocrystals, cellulose nanofibrils and bacterial nanocellulose. Results evidence the astonishing increase in nanocellulose patents since 2010, and specially within the last three years surveyed (i.e. 2015-2017), when published documents accounted for ca. 70 % of the total number of patents published since 2010. Besides patent timelines, data is analysed in terms of patent owners, countries of application, and citing number.

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The morphology of cellulose nanofibrils (CNFs), the rheological characteristics of their dispersions, and the corresponding relationships, are fundamental for understanding the properties of the material. This work aims at understanding how the morphological characteristics of the CNFs affect the rheology of the dispersions in the dilute region and to establish a relationship between both properties. A strong relationship was observed between the intrinsic viscosity of the CNF dispersions and their aspect ratio, which can be correlated through the expression ρ[η]=0.051p1.85. When comparing the model obtained in this work to the wormlike chain model, it was possible to verify that these models are independent of the flexibility of the CNFs. Regarding the fibrillation process, the dynamic viscosity only reflects part of the behavior of the morphological properties of the CNFs and does not provide reliable data that would allow these characteristics to be inferred, while the intrinsic viscosity does allow this relationship.

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BACKGROUND: The rising concern with environmental preservation has led to increasing interest in biodegradable polymer composites from renewable sources, such as cellulose and its derivatives. The use of nanocellulose is an innovative food packaging trend. DISCUSSION: This paper presents an overview and discusses the state of the art of different nanocellulose materials used in food and food packaging, and identifies important patents related to them. It is important to consider that before marketing, new products must be proven safe for consumers and the environment. CONCLUSION: Several packaging materials using nanocellulose have been developed and shown to be promising for use as active and intelligent materials for food packaging. Other nanocellulose products are under investigation for packaging and may enter the market in the near future. Many countries have been adjusting their regulatory frameworks to deal with nanotechnologies, including nanocellulose packaging.

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Cocoa shell was evaluated as a precursor for cellulose nanofibrils (NFCs) using mechanical defibrillation. Its morphology was analysed using optical microscopy and scanning electron microscopy with field emission. Rheological and mechanical behaviour were evaluated through flow curves with a strain rate ranging from 0 to 300 s-1 at 25 °C and by means of oscillatory frequency sweeps (0.01 Hz-10 Hz) and shear stress (3 Pa). The thermal-mechanical behaviour was determined by a temperature sweep with a heating rate of 3 °C min-1 and a temperature range of 25 °C-100 °C. Micrographs identified the presence of protoxilem with a mean diameter of 23.34 nm. The flow curve showed the characteristic behaviour of a pseudoplastic fluid. The storage module (G') and the loss modulus (G″) were dependent on the frequency applied, indicating that the material exhibits a weak gel characteristic. The viscoelastic characteristics were influenced by temperature. Therefore, cocoa shell is a new alternative in the production of nanocellulose.

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The objective of this work was to prepare bio-based thin films and evaluate the additions of magnetite and glycerol on the physico-chemical (flexibility, wettability and barrier properties) and dielectric properties of cellulose/chitosan-based films. The films were prepared by solution casting and presented a suitable dispersion of the constituents observed by SEM and FTIR. The films were thermally stable up to 150 °C and had a higher flexibility, wettability and lower barrier properties upon addition of glycerol. The calculated dielectric constant (εr) for the composite films was based on measurements of capacitance, at 100 and 1000 Hz, with the additions of magnetite and glycerol more than doubling the εr increasing the charge storage capacity. The bio-based thin films have potential to be used as insulators in capacitors on the production of green electronics thus, reducing toxic and nonrenewable e-waste generation.

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Fique fibers are extracted from Furcraea spp. leaves, with 5% average mass yield, using mechanical decortication. Juice, pulp and tow, the by-products of this process, amount 95% of the leaf weight and are considered waste. We extracted cellulose nanofibrils (CNF) from Fique tow, via ultrasound-assisted TEMPO followed by mechanical disintegration with sonication. Fique CNF exhibit diameters around 100 nm, degree of oxidation (DO) of 0.27 and surface charge density (σ) of 1.6 mmol/g. Fique CNF aqueous suspensions show optical birefringence and high colloidal stability due to a high ζ potential (-53 mV). The morphology, chemical structure, crystallinity and phase transitions of Fique CNF were studied using FESEM, IR-ATR, XRD and TGA. We observed that the delignification pretreatment and the TEMPO reaction assisted by ultrasound significantly increase Fique CNF σ and ζ potential, in contrast with the oxidation carried out without ultrasound or with raw (lignified) tow.

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Commercialization of cellulose nanofibrils (CNFs) involves addressing various challenges. Among them, wet storage and transport of CNFs due to their irreversible agglomeration when dehydrated (i.e., hornification) is a pressing issue, as it increases transportation costs. Various alternatives have been proposed in literature, some of which require the use of high-energy treatments to facilitate their redispersion after drying, while others may be inadequate when applied to food and pharmaceutical applications. The present work examines a new approach that involves using poly (vinyl alcohol) (PVA) as a capping agent to redisperse CNFs. Different CNF to PVA ratios were used, and redispersed samples were analyzed in terms of their morphological, physicochemical and rheological properties to assess changes occurring during processing. Results show that the ratio of CNFs to PVA affects the final properties of the redispersed product, when the ratio 1:2.5 was used, the redispersed product closely resembles the never dried sample.

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This paper investigates the use of an aqueous dispersion of polyethylene copolymer with a relatively high content of acrylic acid as a compatibilizer and as an alternative medium to obtain polyethylene CNF nanocomposites. The CNF content was varied from 1 to 90wt% and the appearance, optical, thermal, mechanical and rheological properties, as well the morphology of the films were evaluated. The PE/CNF films are transparent up to 20wt% of NFC indicating a good dispersion of CNF, but a poor distribution, with PE-rich and CNF-rich regions observed by SEM. Improved mechanical properties were achieved, with a 100% and 15,900% increase in the Young's modulus with 1wt% and 90wt% NFC, respectively. The rheological behavior indicated good melt processability. According to these results, aqueous polyolefin dispersions seem to be a promising, easy and relatively fast route for obtaining cellulose/polyolefins nanocomposites with low to high contents of cellulose nanofibrils.