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openaire: EC/H2020/788489/EU//BioELCell Natural biopolymers have become key players in the preparation of biodegradable food packaging. However, biopolymers are typically highly hydrophilic, which imposes limitations in terms of barrier properties that are associated with water interactions. Here, we enhance the barrier properties of biobased packaging using multilayer designs, in which each layer displays a complementary barrier function. Oxygen, water vapor, and UV barriers were achieved using a stepwise assembly of cellulose nanofibers, biobased wax, and lignin particles supported by chitin nanofibers. We first engineered several designs containing CNFs and carnauba wax. Among them, we obtained low water vapor permeabilities in an assembly containing three layers, i.e., CNF/wax/CNF, in which wax was present as a continuous layer. We then incorporated a layer of lignin nanoparticles nucleated on chitin nanofibrils (LPChNF) to introduce a complete barrier against UV light, while maintaining film translucency. Our multilayer design which comprised CNF/wax/LPChNF enabled high oxygen (OTR of 3 ± 1 cm3/m2·day) and water vapor (WVTR of 6 ± 1 g/m2·day) barriers at 50% relative humidity. It was also effective against oil penetration. Oxygen permeability was controlled by the presence of tight networks of cellulose and chitin nanofibers, while water vapor diffusion through the assembly was regulated by the continuous wax layer. Lastly, we showcased our fully renewable packaging material for preservation of the texture of a commercial cracker (dry food). Our material showed functionality similar to that of the original packaging, which was composed of synthetic polymers.

This perspective gives an overview of recent progress in thefield of photocured polymer composites based on variousforms of nanocelluloses, with a focus on cellulose nanofibrils. The manufacturing processes and performances of these nanocellulosecomposites are detailed, comprising solvent-assisted mixing processes, emulsification, coating and casting processes, preformimpregnation, and 3D printing. Attention is also paid to life-cycle engineered approaches to improve their sustainability. Thesematerialsfind applications in numerous domains, primarily as protective coatings but also as diffusion barrier composites andfilmsfor packaging and encapsulation of electronics, as composite hydrogels for biomedical applications, and as membranes for battery technologies.

openaire: EC/H2020/788489/EU//BioELCell Funding Information: This work received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 788489, ‘BioElCell’). J.J.R. is the recipient of an Australian Research Council Future Fellowship (project no. FT210100669) funded by the Australian government and JSPS Fellowship P20373 from the Japanese Society for the Promotion of Science. B.L.T. is the recipient of the Khalifa University of Science and Technology (KUST) Faculty Startup Project (Project: FSU-2022-021). Publisher Copyright: © 2022, Springer Nature Limited. The unprecedented accumulation of plastic waste forms a serious threat to the biosphere, and current recycling efforts are not living up to their promise. Replacements for synthetic plastics are therefore critically needed, which has led to a rapid growth in research surrounding the development of sustainable materials, such as bioproducts. Still, commercialization has been limited, as knowledge gaps separating publicly funded research from industrial implementation need to be overcome. The food-packaging sector is currently undergoing drastic transformations in phasing out plastics and can therefore provide a blueprint for catalysing the adoption of bioproducts that could be applicable to other sectors. Non

Cellulose nanocrystals (CNCs) are ideal rheological modifiers for aqueous oil and gas extraction fluids. CNCs are typically produced with sulfuric acid and their aqueous suspensions have uniform and predictable properties under ambient conditions; however, drastic changes occur at elevated temperatures. Herein, the effects of high temperature treatments (ranging from 80 to 180 °C for 1 h to 7 days) on the properties (including uniformity, colloidal stability, and color) of sulfated, phosphated, and carboxylated CNC suspensions were studied. Additionally, cellulose molecular weight, and CNC surface charge content and crystallinity index were quantified before and after heating. CNCs underwent few morphological changes; their molecular weight and crystallinity index were largely unchanged under the conditions tested. Their surface charge content, however, was significantly decreased after heat treatment which resulted in loss of colloidal stability and aggregation of CNCs. The largest change in suspension properties was observed for sulfated CNCs whereas CNCs with a combination of sulfate and phosphate esters, or carboxylate groups, were less affected and maintained colloidal stability at higher temperatures. In fact, desulfation was found to occur rapidly at 80 °C, while many carboxylate groups persisted at temperatures up to 180 °C; calculated rate constants (based on second order kinetics) suggested that desulfation is 20 times faster than decarboxylation but with a similar activation energy. Overall, this study elucidates CNC suspension behavior after heat exposure and demonstrates routes to produce CNCs with improved high temperature performance.

International audience; Today’s environmental concerns are pressuring industries to substitute paper-based materials in place of plastics in many sectors including packaging. However, assembling papers and paperboards using environmentally friendly solutions remains a technological challenge. In this context, ultrasonic (US) welding is an alternative to adhesives. In this work, the potential of US welding to assemble folding boxboards was investigated. Folding boxboards are commonly coated to enhance printability. This coating is generally composed of mineral pigments (85 to 90%) and polymer binders (10 to 12%). This study evaluated whether the presence of the coating layer allows the assembly of paperboards by US welding. Results indicated that welding coated folding boxboards is possible provided that coating weight and binder content are high enough. The mechanical performances of the welded boards met the requirements of most packaging applications. Adhesion in the welded joint resulted from a combination of thermoplastic (melting and flowing of the binder) and thermoset (degradation reactions) effects. However, it was not possible to assemble coated folding boxboards without degrading the welding zone. While the materials and process need to be optimized, this work represents a big step forward toward the adhesive-free assembling of paper-based materials.

There is an ever-increasing interest toward utilizing nanocellulose as barrier coatings and films, and recent studies have underlined the efficiency of using innovative fibrillation processes such as twin-screw extrusion with an enzymatic pretreatment for producing nanocellulose suspensions with solid contents as high as 20 wt %, which can lead to faster coating speeds and reduced drying energy costs. The current work aims at understanding the factors that influence high-throughput processability of high-solid-content nanocellulose during roll-to-roll coating. The rheological properties of 12.5, 10, and 7.5 wt % suspensions were evaluated across a wide range of shear rates and geometries (rotational, pipe, and slot). The influence of dispersants [carboxymethyl cellulose (CMC) and sodium polyacrylate (NaPA)] on the rheology and coating quality was assessed. A Casson-power-cross model is proposed to explain the rheological behavior across a wide shear rate range and is used to predict useful parameters, viz., yield stress, transition shear rate, and power-law index at high shear rates. Finally, a 12.5 wt % nanocellulose suspension with CMC or NaPA dispersant was roll-to-roll-coated on paperboard using a slot-die applicator. CMC addition had a positive influence on the yield stress, thixotropy, and water release and, therefore, resulted in a better mineral oil and grease barrier of the coated samples compared to the rest.

TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl)-oxidized cellulose nanofibrils (T-CNF) and silver nanowires (Ag NWs) were formulated as active inks. Their rheological properties were investigated to design optimal conditions for processing by the screen-printing process, with the aim of preparing antibacterial patterns. Rheological experiments mimicking the screen-printing process were applied to different ink formulations to investigate their thixotropic and viscosity properties. The experiments conducted at 1wt% total mass content and different ratios of T-CNF/Ag NWs showed that the recovery (%), the recovery time and the viscosity are formulation dependent. A ratio 2:1 (T-CNF/Ag NWs) and total mass content of 2.5wt% were then selected to prepare an ink suitable for screen printing. Printing defects were corrected by addition of water-soluble polymer hydroxypropyl methylcellulose (HPMC). The selected formulation printed on flexible polyethylene terephthalate (PET) substrate displayed a 67.4% antibacterial activity against E. coli in a standard contact active test, with a transparency superior to 70%, proving the promising features of the developed solution for active packaging applications.

Characterizing the mechanical properties of polymer coatings typically requires access to specialty equipment, the analysis through which can be tedious despite instrumental precision. An alternative method reported in the literature, strain-induced elastic buckling instability for mechanical measurements (SIEBIMM), is a high throughput, facile yet accurate method, used to characterize the Young’s modulus of supported films and coatings. SIEBIMM can easily be implemented in both academic and industrial settings. Hypothesis: We hypothesize that the SIEBIMM method has an upper coating thickness limit beyond which the assumptions and practicality of the method are no longer valid. Experiments: The Young’s moduli of model polyvinyl alcohol coatings (on polydimethylsiloxane substrates) with thicknesses ranging from 67 nm to 40 µm were determined using the SIEBIMM method and the data were subjected to a rigorous statistical analysis. Findings: SIEBIMM could accurately characterize coatings up to 35 µm thick. The Young’s modulus of all coatings ≤ 35 µm was 1.6 ± 0.1 GPa at 50% RH, which agreed with free-standing polyvinyl alcohol films measured by traditional tensile testing. For the method to be used on thicker coatings, it is essential to consistently measure coating thickness and buckling wavelength at the same location to minimize potential error.

In the current context, the development of bio-based and high-performance materials is one of the main research priorities. This study aims to combine the outstanding properties of cellulose nanofibrils (CNFs) or nanocrystals (CNCs) with those of bio-based poly(lactic acid) (PLA). Three-phase multilayered materials (TMLs) were built up by complexing a dry CNF- or CNC-based film with two PLA sheets, using a heat-pressing process. Before the preparation of the nanocellulosic films, CNFs and CNCs were modified by the adsorption of a rosin-based nanoemulsion. The rosin mixture as a natural compound is of interest because of its low cost, renewability, hydrophobicity, and its antimicrobial and antioxidant properties. After demonstrating the efficiency of the complexing procedure, we investigated the barrier properties of the multilayered materials against both oxygen and water vapor, with highly encouraging results. In fact, the presence of nanocellulose as an inner layer between the two PLA films significantly enhanced the oxygen barrier, with a decrease in oxygen permeability comprised between 84 and 96% and between 44 and 50% for neat nanocelluloses and nanocelluloses with rosins as the inner layer, respectively. On the other hand, the antioxidant properties of the final multilayered materials including rosins were highlighted, with a highly encouraging radical scavenging activity close to 20%. Because of the simplicity and the efficiency of the proposed method, this study paves the way toward the development of hybrid multimaterials that could be highly attractive for food packaging applications.

In this study, the grafting of 1-methyl-3-phenylpropylamine (1-M-3-PP) on cellulose nanocrystals (CNCs) via a two-step reaction route was investigated and compared with physico-chemical surface adsorption. The first step involved subjecting CNCs to a 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO)-mediated oxidation. The carboxylic groups present on recovered oxidized TEMPO-CNC were quantified by several characterization methods (conductometric titration, elemental analysis, and X-ray photoelectron spectroscopy), and a degree of oxidation close to 0.2 was found. The second step was an amidation reaction carried out in an aqueous medium under mild conditions and in the presence of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC)/N-hydroxysuccinimide (NHS) as catalyst. The recovered modified CNCs after amidation reaction with 1-M-3-PP (CNC-1-M-3-PP) were extensively washed and then characterized. The amount of grafted molecules was determined by several techniques like X-ray photoelectron spectroscopy (XPS), and the calculated degree of substitution was found to be close to 0.05 with respect to the bulk CNC. This low amount is sufficient to enhance the modified CNC dispersion and their colloidal stabilization in organic solvents, allowing the preparation of nanocomposites. Furthermore, such CNC-1-M-3-PP units with aromatic molecules attached to it can find applications in barrier materials in which the sorption of aromatic molecules can be very useful.

The aim of this work is to study and compare the influence of different nanofibrillation processes on the properties of cellulose nanofibers from wheat straw, and analyze the effect of the lignin in the nanocellulose quality and on the characteristics of the films produced. Wheat straw was subjected to a soda (NaOH) pulping process to obtain unbleached cellulosic pulp. The cellulosic pulp was bleached with NaClO2 in order to remove the lignin of the fiber. Both bleached and unbleached pulps were used to obtain nanocellulose using mechanical pretreatment (PFI refining) and treatments, (high pressure homogenization, twin-screw extruder and ultrafine friction grinder). The effect of the nanofibrillation treatments and the residual lignin content on cellulose nanofiber production was analyzed by means of a deep characterization. A multi-factorial quality index was used to score the cellulose nanofibers produced to enable a benchmarking study between different sources, processes and characteristics. In addition, an energetic study of the production process was carried out for the different treatments. The different nanofibers were used to produce cellulose nanofiber-based films and characterized in order to establish a relationship between the characteristics of cellulose nanofibers and the characteristics of the final product.

International audience; High barrier and mechanically resistant three-dimensional (3D) cellulosic objects were produced using cellulose nanofibrils (CNF) and the molded cellulose process. The main objective is to improve properties of objects made by molding conventional papermaking fibers such as egg box. This well-known process, currently used for the production of low-end cellulose packaging, was simulated using 3Dprinted polycarbonate porous molds, dewatering, and heat compression stages. CNF produced by twin screw extrusion, which possess good barrier properties and transparency, were used as the base material, and different methods were used to form the cellulosic mats. Different drying techniques were tested in order to produce a transparent object and minimize the shrinkage of CNF upon drying, that is, oven-drying, thermopressing, microwave-drying, freeze-drying, or a combination. CNF cellulosic mats were easily formed, but due to the important shrinkage of CNF, none of the mat formation or drying techniques yielded transparent and dimensionally stable 3D objects.; Des objets cellulosiques tridimensionnels (3D) avec hautes propriétés barrière et mécaniquement résistants ont été produits à l'aide de nanofibrilles de cellulose (CNF) et du procédé de moulage de la cellulose. L'objectif principal est d'améliorer les propriétés des objets fabriqués par moulage de fibres papetières classiques telles que la boîte à œufs. Ce procédé bien connu, actuellement utilisé pour la production d'emballages cellulosiques bas de gamme, a été simulé à l'aide de moules poreux en polycarbonate imprimés en 3D, d'étapes de déshydratation et de compression thermique. Le CNF produit par extrusion à double vis, qui possède de bonnes propriétés de barrière et de transparence, a été utilisé comme matériau de base, et différentes méthodes ont été utilisées pour former les matelas cellulosiques. Différentes techniques de séchage ont été testées afin de produire un objet transparent et de minimiser le rétrécissement du CNF lors du séchage, c'est-à-dire le séchage au four, le thermopressage, le séchage par micro-ondes, la lyophilisation ou une combinaison. Les matelas cellulosiques CNF se formaient facilement, mais en raison du rétrécissement important du CNF, aucune des techniques de formation ou de séchage du tapis n'a donné des objets 3D transparents et dimensionnellement stables.

openaire: EC/H2020/788489/EU//BioELCell Funding Information: The authors would like to thank S-Fly and Die Wurm Farm for providing the raw materials needed for this study and Tuyen Nguyen for the fluidization of the different ChNFs. LGP2 is part of the LabEx Tec 21 (Investissements d’Avenir - grant agreement no. ANR-11-LABX-0030) and of the PolyNat Carnot Institute (Investissements d’Avenir - grant agreement no. ANR-16-CARN-0025-01). This work was supported by Grenoble INP, “Bourse Présidence”, and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 788489). O.J.R. also acknowledges the Canada Excellence Research Chair initiative and the Canada Foundation for Innovation (CFI). Support from the Austrian Biorefinery Center Tulln (ABCT) is gratefully acknowledged. Publisher Copyright: © 2021 American Chemical Society. Nowadays, environmental concerns make us rethink the way that we live and eat. In this regard, alternative protein sources are emerging; among them, insects are some of the most promising alternatives. Insect farming is still an infant industry, and to improve its profitability and environmental footprint, valorization of the byproducts will be a key step. Chitin as the main polysaccharide in the exoskeleton of insects has a great potential in this regard and can be processed into high value-added materials. In this study, we extracted and fibrillated chitin fibers from fly larvae (Hermetia illucens) and compared them with commercial chitin from shrimp shells. A mix of chitin and cellulose fibers was also extracted from mealworm farming waste. The purified chitinous fibers from different sources had similar chemical structures as shown by Fourier transform infrared and nuclear magnetic resonance spectroscopies. After mechanical fibrillation, the nanostructures of the different nanofibers were similar with heights between 9 and 11 nm. Chitin nanofibers (ChNFs) from fly larvae presented less nonfibrillated fiber bundles than the shrimp-derived analogue, pointing toward a lower recalcitrance of the fly larvae. ChNF suspensions underwent different film-forming protocols leading to films with tensile strengths of 83 ± 7 and 71 ± 4 MPa for ChNFs from shrimp and fly, respectively. While the effect of the chitin source on the mechanical properties of the films was demonstrated to be negligible, the presence of cellulose nanofibers closely mixed with ChNFs in the case of mealworm led to films twice as tough. Our results show for the first time the feasibility of producing ChNFs from insect industry byproducts with high potential for valorization and integral use of biomass.

Phosphorylated cellulose nanofibrils (CNFs) were produced using a twin-screw extruder (TSE). The energy efficiency was compared with that of an ultra-fine grinder (UFG). CNFs at different solid contents were produced (10 wt% for the TSE and 2 wt% for the UFG), and their quality was compared using several characterization tests, such as optical microscopy, atomic force microscopy or MorFi fiber analyser. CNF nanopapers with high a Young’s modulus (14 GPa) and high transparency were successfully manufactured using CNFs produced by the TSE. The efficiency of the TSE was improved by using phosphorylated pulp instead of mechano-enzymatically treated pulp. The results show that phosphorylated CNFs can be easily produced at the industrial scale via twin-screw extrusion and present new functionalities such as fire-retardant properties, which are useful in many applications.

In this study, an innovative and green process to produce cellulose nanofibers (CNFs) is proposed. CNFs are usually produced via mechanical, enzymatic, and/or chemical treatment such as (2,2,6,6-te...

Cellulose nanofibrils (CNF) are renewable bio-based materials with high specific area, which makes them ideal candidates for multiple emerging applications including for instance on-demand drug release. However, in-depth chemical and structural characterization of the CNF surface chemistry is still an open challenge, especially for low weight percentage of functionalization. This currently prevents the development of efficient, cost-effective and reproducible green synthetic routes and thus the widespread development of targeted and responsive drug-delivery CNF carriers. We show in this work how we use dynamic nuclear polarization (DNP) to overcome the sensitivity limitation of conventional solid-state NMR and gain insight into the surface chemistry of drug-functionalized TEMPO-oxidized cellulose nanofibrils. The DNP enhanced-NMR data can report unambiguously on the presence of trace amounts of TEMPO moieties and depolymerized cellulosic units in the starting material, as well as coupling agents on the CNFs surface (used in the heterogeneous reaction). This enables a precise estimation of the drug loading while differentiating adsorption from covalent bonding (∼1 wt% in our case) as opposed to other analytical techniques such as elemental analysis and conductometric titration that can neither detect the presence of coupling agents, nor differentiate unambiguously between adsorption and grafting. The approach, which does not rely on the use of 13C/15N enriched compounds, will be key to further develop efficient surface chemistry routes and has direct implication for the development of drug delivery applications both in terms of safety and dosage., DNP-enhanced solid-state NMR unravels the surface chemistry of functionalized nanocellulose.

The breakdown and buildup mechanisms in concentrated cellulose nanocrystal (CNC) suspensions under shear and during relaxation upon cessation of shear were accessed by small-angle X-ray and light scattering combined with rheometry. The dynamic structural changes over nanometer to micrometer lengthscales were related to the well-known three-regime rheological behavior. In the shear-thinning regime I, the large liquid crystalline domains were progressively fragmented into micrometer-sized tactoids, with their cholesteric axis aligned perpendicular to the flow direction. The viscosity plateau of regime II was associated to a further disruption into submicrometer-sized elongated tactoids oriented along the velocity direction. At high shear rate, regime III corresponded to the parallel flow of individual CNCs along the velocity direction. Upon cessation of flow, the relaxation process occurred through a three-step buildup mechanisms: i) a fast reassembling of the individual CNCs into a nematic-like organization established up to micrometer lengthscales, ii) a slower formation of oriented large cholesteric domains, and iii) their isotropic redistribution.

International audience; Several naturally occurring biological systems, such as bones, nacre or wood, display hierarchical architectures with a central role of the nanostructuration that allows reaching amazing properties such as high strength and toughness. Developing such architectures in man-made materials is highly challenging, and recent research relies on this concept of hierarchical structures to design high-performance composite materials. This review deals more specifically with the development of hierarchical fibres by the deposition of nano-objects at their surface to tailor the fibre/matrix interphase in (bio)composites. Fully synthetic hierarchical fibre reinforced composites are described, and the potential of hierarchical fibres is discussed for the development of sustainable biocomposite materials with enhanced structural performance. Based on various surface, microstructural and mechanical characterizations, this review highlights that nano-objects coated on natural fibres (carbon nanotubes, ZnO nanowires, nanocelluloses) can improve the load transfer and interfacial adhesion between the matrix and the fibres, and the resulting mechanical performances of biocomposites. Indeed, the surface topography of the fibres is modified with higher roughness and specific surface area, implying increased mechanical interlocking with the matrix. As a result, the interfacial shear strength (IFSS) between fibres and polymer matrices is enhanced, and failure mechanisms can be modified with a crack propagation occurring through a zig-zag path along interphases.

This paper presents optical transparent CPW antennas designed for 5G telecommunications obtained by an additive printing process. This optical transparency has been obtained by meshing the antenna. The influence of the meshing strategy on the antenna performances is explored, by investigating two geometrical models of antennas and in three different meshing. The adaptation, radiation performance and optical transmittance have been characterized. The best trade-off between transparency and radiation performance is presented through a plot connecting the realized gain and the optical transparency. The square meshing features the best trade-off with more than 65% of optical transparency for 2 dBi in realized gain.

International audience; TEMPO-Oxidized cellulose nanofibrils (toCNF), in the form of highly entangled network such as membrane or cryogels, have proven to be of interest for various applications, including drug release or purification by pollutant adsorption. β-Cyclodextrins (β-CDs) have the ability to form inclusion complexes with large amount of hydrophobic molecules, and are considered as a promising way to bring new functionalities to these materials, by reducing drug burst release effect or improving the pollutant adsorption properties. The study of the adsorption β-CDs onto toCNF is then crucial to design toCNF/β-CDs materials, but is very complex due to the chemical proximity between these compounds. In this study, we develop toCNF cryogels containing various types of β-CDs derivatives by physical adsorption. Different protocols for analyzing the interactions between these compounds, such as Isothermal Titration Calorimetry (ITC), Quartz-Crystal Microbalance with dissipation monitoring (QCM-d) and a Phenolphthalein-based protocol (PhP protocol) have been performed. Adsorption between β-CD and toCNF was proven at two different temperatures with ITC. QCM-d measurements allowed measuring adsorption of different β-CDs derivatives onto toCNF, with higher adsorption measured for the modified β-CDs, and with estimated binding capacity ranging from 13.4 to 47.6 μmol/g toCNF. PhP protocol allowed us to monitor the amount of β-CDs released in aqueous environment, highlighting a lower release for modified β-CDs onto toCNF, and the results were consistent with the estimated binding capacity. This quantification of the binding adsorption capacity of various β-CDs is key results for optimizing the design of toCNF/β-CDs materials.

The interest toward nanocellulose materials has exponentially grown in recent years. Their scope of applicability is wide and diversified, from emulsion to mechanical reinforcement. The ability of nanocellulose to be used as a substrate or as a dispersing agent is increasingly exploited in the production of flexible electronics and more recently in electromagnetism and radio frequencies (RF) application. Furthermore, in the meantime, the development of more eco-friendly electronic devices is required to answer current societal and political challenges. Both aspects hence make of nanocellulose a high potential material for electronic field and especially for electromagnetism and RF. The aim of this chapter is thus to give a broad overview of the use of nanocellulose in two field applications: electromagnetic interference shielding and RF devices.

The application of sensitive gas sensors manufactured in high volume at low cost is of great interest due to an extensive array of potential applications. Such areas include industrial processing, biotechnology and intelligent food packaging. This work reports a straightforward and versatile technique using screen-printing and drop-casting processes, to produce gas sensors on a flexible plastic substrate, based on a combination of metal organic framework and graphene-carbon materials. We demonstrate a sensitive and stable ammonia sensor (4.6% maximal response) over a range from 20 to 100 ppm. The sensitivity of the optimized formulation is 36 times higher than a carbon–graphene only sensor and makes the developed devices suitable for intelligent packaging. The sensor production process is fast, reliable and low-cost and so there is a strong potential for the process principles to be adapted industrially for a different gas target or application.

International audience; In this study, a new approach to optimize the cellulose nanocrystals (CNCs) extraction using acidic natural deep eutectic solvents (NADES) was introduced using, for the first time, design of experiment method. Choline chloride:oxalic acid dihydrate with a molar ratio of 1:1 was used to extract CNCs. Then, three most important parameters were varied to design the experiment: (i) cotton fibre concentrations, (ii) temperature and (iii) treatment time. Two outcomes were studied: the CNC yield and the crystallinity. The mathematical model for crystallinity perfectly described the experiments, while the model for CNC yield provided only a tendency. For a reaction time of 6 h at 95°C with a fibre concentration of 2%, the expected optimum CNC yield was approximately 35.5 ± 2.7% with a crystallinity index of 80 ± 1%. The obtained experimental results confirmed the models with 43.6 ± 1.9% and 81 ± 1% for the CNC yield and the crystallinity index, respectively. This study shows that it is possible to predict the CNC yield CNC and their crystallinity thanks to predictive mathematical models, which gives a great advantage to consider in the near future a scale up of the extraction of cellulose nanocrystals using this original family of green solvents.

International audience; This work is focused on the modification of the interphase zone in short flax fibres / polypropylene (PP) composites by a bio-inspired modification of fibres called “nanostructuration” that uses the adsorption of biomass by-products, i.e. cellulose nanocrystals (CNC) and xyloglucan (XG), to create hierarchical flax fibres. The wettability and interfacial adhesion study reveals a strong decrease in the polar character of CNC modified flax fibres, hence increasing the work of adhesion with PP. Moreover, combining XG/CNC modified interphases with MAPP coupling agent enhances the ultimate mechanical properties of biocomposites with higher tensile strength and work of rupture, and modifies failure mechanisms as revealed by in situ micro-mechanical tensile SEM experiments. Bio-based hierarchical composites inspired by naturally occurring nanostructures open a new path for the development of sustainable composites with enhanced structural properties.

openaire: EC/H2020/788489/EU//BioELCell Cellulose (CNF) and chitin (ChNF) nanofibers are known to form materials that are both tough and strong. In this study, we hypothesize that the inertness of networks produced from CNF and ChNF makes them ideal templates for heterogeneous reactions and in situ formation of nanoarchitectures. We expand nanoparticle templating on polysaccharide colloids by introducing a new and facile process that leads to the growth of organic nanoparticles on CNF and ChNF in aqueous media. The process, based on solvent shifting supported on solid interfaces, is demonstrated by direct observation of lignin nanoparticles that are further used for their photocatalytic activity. Importantly, the dynamics of nanoparticle nucleation and growth is correlated with the surface chemistry of the templating nanopolysaccharides. Electrostatic repulsion between the deprotonated lignin molecules and the slightly negative CNF support led to limited adsorption and was effective in producing free (nonbound) lignin nanoparticles (28 ± 7 nm) via precipitation. In contrast, the stronger interfacial interactions between the positively charged ChNF and lignin molecules facilitated instantaneous and extensive lignin adsorption, followed by nucleation and growth into relatively larger nanoparticles (46 ± 17 nm). The latter were homogeneously distributed and strongly coupled to the ChNF support. Overall, we introduce lignin nanoparticle nucleation and growth on renewable nanopolysaccharides, offering an effective route toward in situ synthesis of highly functional fibrils and related cohesive films that offer a great potential in packaging and other applications.

Nowadays, drug encapsulation and drug release from cellulose nanofibrils systems are intense research topics, and commercial grades of cellulose nanomaterials are currently available. In this work we present an ester-containing prodrug of metronidazole that is covalently bound to cellulose nanofibrils in aqueous suspension through a two-step immobilization procedure involving green chemistr y principles. The presence of the drug is confirmed by several characterization tools and methods such as Raman spectroscopy, elemental analysis, Dy-namic Nuclear Polarization enhanced NM R . This technique allow s enhancing the sensitivity of NM R by several orders of magnitude. It has been used to study cellulose nanofibrils substrates and it appears as the ultimate tool to confirm the covalent nature of the binding through thiol-yne click chemistry. Moreover, the ester function of the immobilized prodrug can be cleaved by specific enzyme activity thus allowing controlled drug release.

International audience; In this work, we present an innovative strategy for the grafting of an antibacterial agent onto nanocellulose materials in supercritical carbon dioxide (scCO2). Dense cellulose nanofibril (CNF) nanopapers were prepared and subsequently functionalized in supercritical carbon dioxide with an aminosilane, N-(6-aminohexyl)aminopropyltrimethoxysilane (AHA-P-TMS). Surface characterization (X-ray photoelectron spectroscopy, contact angle, ζ-potential analysis) evidenced the presence of the aminosilane. The results show that the silane conformation depends on the curing process: a nonpolycondensed conformation of grafted silane with the amino groups facing outwards was favored by curing in an oven, while the curing step performed in scCO2 yielded CNF structures with the alkyl chain facing outwards. The grafted nanopapers exhibited antibacterial activity, and no antibacterial agent was released into the media. Furthermore, these materials proved to benefit from low cytotoxicity. This study offers a proof of concept for the covalent grafting of active species on nanocellulose structures and the control of aminosilane orientation using a green and controlled approach. These newly designed materials could be used for their antibacterial activity in the biomedical field. Thus, perspectives for topical administration and design of wound dressing could be envisaged.

We report on gelatin films incorporating rosin-grafted cellulose nanocrystals (r-CNCs), which fulfill the most relevant requirements for antimicrobial packaging applications. Transparent gelatin/r-CNCs bionanocomposite films (0.5–6 wt% r-CNCs) were obtained by solution casting and displayed high UV-barrier properties, which were superior to the most used plastic packaging films. The gelatin/r-CNCs films exhibited a moderate water vapor permeability (0.09 g mm/m2 h kPa), and high tensile strength (40 MPa) and Young's modulus (1.9 GPa). The r-CNCs were more efficient in improving the optical, water vapor barrier and tensile properties of gelatin films than conventional CNCs. Grafting of rosin on CNCs resulted in an antimicrobial nanocellulose that inhibited the growth of Staphylococcus aureus and Escherichia coli. The antibacterial properties of r-CNCs were sustained in the gelatin films, as demonstrated by agar diffusion tests and proof-of-principle experiments involving cheese storage. Overall, the incorporation of r-CNCs as active fillers in gelatin films is a suitable approach for producing novel eco-friendly, antimicrobial packaging materials., This research was made possible thanks to the facilities of the Laboratory of Pulp and Paper 479 Science and Graphic Arts (LGP2) that is part of the LabEx Tec 21 (Investissements d'Avenir - grant 480 agreement n°ANR-11-LABX-0030) and of PolyNat Carnot Institute (Investissements d'Avenir - 481 grant agreement n° ANR-16-CARN-0025- 0), and Plant Macromolecule Research Center 482 (CERMAV) for the support to this work. This study was financed in part by CNPq, SISNANO 26 483 (MCTI), FINEP, Embrapa AgroNano research network (Embrapa), Coordenação de 484 Aperfeiçoamento de Pessoal de Nível Superior - Brazil (CAPES) [Finance Code 001] and by the 485 São Paulo Research Foundation (FAPESP) [grant numbers 2016/03080-2, 2017/18725-2 and 486 2018/00278-2, 2018/10899-4, 2018/22214-6, 2018/18953-8]. We would like to thank Berthine 487 Khelifi , Cécile Sillard and Thierry Encinas from Grenoble Institute of Technology for their 488 expertise in providing SEM imaging, XPS and XRD analyses, respectively.

International audience; 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 /gfibres 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.

Crosslinking with genipin increases the acidic stability of chitosan-based materials, opening an opportunity to explore new applications. In this work, the viability of using chitosan-genipin solutions on cellulose-based materials coating was studied. Non-calendered paper and cardboard were used as raw materials. Different number of chitosan-genipin coating layers (1, 3, 6, 20, and 30) were applied and their influence on the materials mechanical, physicochemical, and barrier properties was studied. The small thickness and basis weight of non-calendered paper resulted in an inefficient adhesion of chitosan-genipin coating to the cellulose fibers. However, in cardboard, chitosan-genipin created a dense layer onto the cellulosic-fibers surface without impairing their mechanical properties. It conferred a greenish color, whose intensity increased with the layers number. The chitosan-genipin coating decreased the cardboard air and water vapor permeability up to 71 % and 52 %, respectively, and acted as a physical barrier for cardboard compounds leaching, being suitable for covering cellulose-based materials. published

Cellulose nanofibrils were efficiently produced from eucalyptus fibers using a combined NaOH and enzymatic treatment followed by a pilot scale grinding process. The structural changes of fibers were assessed after NaOH treatments at 5, 10 and 15 wt% concentrations. A progressive shift from a cellulose I to a cellulose II crystalline structure was observed with X-ray diffraction (XRD) and nuclear magnetic resonance (NMR). The further enzymatic hydrolysis was improved for the NaOH treated samples. The increase of crystallinity indices due to enzymatic hydrolysis was of + 4.7 %, + 3.5 %, and +10.3 % for samples treated with NaOH 5, 10 and 15 wt% respectively, and DP values were drastically reduced to 340, 190 and 166 respectively. A morphological analysis underlined an optimum with the combination of NaOH 10 wt% and enzymatic hydrolysis. This treatment followed by the grinding process resulted in CNF with a rigid structure, with diameters ranging from 10 to 20 nm and lengths between 150 and 350 nm. A multi-scale analysis enabled to study the impact of this combined treatment on CNF properties and energy consumption. A decrease in mechanical properties of nanopapers was observed for the combined treatment and NaOH treatment alone compared to enzymatic hydrolysis alone, with Young's modulus of 8.94, 4.84 and 11.21 GPa respectively. However, optical properties were improved, with transmittance values of 42.2, 15.4 and 7.1 % respectively. This new pretreatment can therefore lead to CNF with tunable properties depending on the application, with possible industrialization thanks to the reduction of energy needs.

This short communication describes the climate change impacts of using cellulose, and more precisely cellulosic fiber-based materials, in food packaging, representing current and emerging industrial state of the art technology, without specific reference to current scientific advances. First, the different types of cellulosic fiber-based packaging materials, which can be used to replace fossil-based packaging materials, are presented for flexible and rigid applications. The focus is on technological solutions with packaging properties that enable the protection of commonly sold food products. The manufacturing processes associated with these cellulosic fiber-based materials is described and the environmental impact assessment of 4 selected case studies presented: stand-up pouches, flexible flow wraps, frozen or chilled food trays, and molded pulp lids. A simplified eco-design Life Cycle Assessment (LCA) was then performed to compare each solution with its fossil-based counterpart. Differences and similarities between the various cellulosic solutions have been identified. Furthermore, the assessment confirms that cellulosic fiber-based materials have reduced environmental impacts as compared to fossil-based counterparts, if a similar packaging weight is obtained. Indeed, all impacts of plastics are between 3 and 5 kg CO2eq/kg, while all impacts of cellulosic fiber-based materials are below 1.5 kg CO2eq/kg.

International audience; This study presents the impregnation in supercritical carbon dioxide (scCO 2) of nanocellulose-based structures with thymol as a natural antimicrobial molecule to prepare bioactive biosourced materials. First, cellulose nanofibrils (CNFs) were used to produce four types of materials (nanopapers, cryogels from water or tert-butyl alcohol suspensions and aerogels) of increasing specific surface area up to 160 m 2 .g-1 thanks to the use of different processes, namely vacuum filtration, freeze-drying and supercritical drying. Secondly, these CNF-based structures were impregnated with thymol in scCO 2 medium using relatively low temperature and pressure of 40°C and 100 bars during 1 hour. The amount of impregnated thymol in the different CNF-materials was investigated by fluorescence spectroscopy, 13 C NMR analysis and gas

International audience; The recent emergence of bio-based nanocomposites makes perfect sense from a technical and environmental point of view. Cellulose nanocrystals (CNCs) are novel bio-based nanomaterials with a wide range of beneficial properties. Their biodegradability, crystallinity, high surface area, and mechanical strength, as well as their highly reactive surface, make them ideal materials as nanofillers in polymeric matrices. However, most the bio-based polymers are hydrophobic, and the hydrophilicity of CNC is therefore a challenge to their incorporation in such matrices. In this study, a new procedure for surface modification of CNC with long aliphatic chains [lauric acid (12 carbons) and stearic acid (18 carbons)] was developed that limits the use of petro-chemicals and facilitates their potential recycling. A study of the dispersion state of CNC in acetone was performed first. Then, grafting efficiency was highlighted by several techniques and quantification of the amount of grafted fatty chains was investigated. Degrees of substitution on the bulk and on the surface of the CNC were calculated between 0.1 and 0.3, which provided enough grafted functions to confer hydrophobic behavior to modified CNCs, as highlighted by the increasing of contact angle from 65° for neat CNC to 80° after modification. Finally, conservation of CNC crystalline structure and morphology was proved by both X-ray diffraction and transmission electron microscopy analyses. Modified CNCs exhibit a crystallinity index close to 86% and length of approximately 350 nm. Thus, crystalline hydrophobic cellulosic nanomaterials were prepared using a more environmentally friendly procedure than those classically found in the literature.

International audience; Cellulose nanocrystals (CNCs) are used to design nanocomposites because of their high aspect ratio and their outstanding mechanical and barrier properties. However, the low compatibility of hydrophilic CNCs with hydrophobic polymers remains a barrier to their use in the nanocomposite field. To improve this compatibility, poly(glycidyl methacrylate) (PGMA) was grafted from CNCs containing α-bromoisobutyryl moieties via surface-initiated atom transfer radical polymerization. The novelty of this research is the use of a reactive epoxy-containing monomer that can serve as a new platform for further modifications or crosslinking. Polymer-grafted CNC-PGMA-Br prepared at different polymerization times were characterized by XRD, DLS, FTIR, XPS and elemental analysis. Approximately 40 % of the polymer at the surface of the CNCs was quantified after only 1 h of polymerization. Finally, nanocomposites prepared with 10 wt% CNC-PGMA-Br as nanofillers in a poly(lactic acid) (PLA) matrix exhibited an improvement in their compatibilization based on SEM observation.

International audience; Depuis les années 90, un important développement des polymères et renforts biosourcés et biodégradables a été observé. Par exemple, le secteur de l’automobile souhaite développer des structures plus légères et augmenter la fraction biosourcée dans ses composites. Les fibres végétales sont d’excellentes candidates avec des propriétés intrinsèques très intéressantes. Il est connu que les propriétés thermomécaniques des matériaux biocomposites dépendent fortement de l’interface fibre/matrice. En revanche, la plupart des matrices polymères sont hydrophobes et apolaires, ce qui implique une très faible adhésion interfaciale avec les fibres naturelles possédant des surfaces majoritairement hydrophiles [1]. L’enjeu de ce travail consiste à créer une interphase hiérarchique plus forte et cohésive dans les biocomposites en assemblant des nanocristaux de cellulose (CNC) avec du xyloglucane (XG) sur un tissu de lin industriel. Le but étant l’augmentation de la quantité de surface disponible des fibres et le renforcement de l’interphase grâce aux dimensions et aux propriétés mécaniques des CNC [2]. Le biopolymère XG est quant à lui utilisé comme agent interfacial entre les fibres de lin et les CNC. Il possède en effet une forte affinité avec la cellulose [3]. Dans cette étude, nous détaillons le comportement en adsorption du XG et des CNC sur un tissu de lin industriel par différentes techniques : microscopie confocale et isothermes d’adsorption (Figure 1). De plus, nous étudions l’effet de cette fonctionnalisation par la mouillabilité des fibres de lin (Tensiomètre K100SF) ainsi que la microstructure (MEB), la micromécanique (IFSS par déchaussement de fibres) et les propriétés mécaniques des biocomposites lin/epoxy (tests de traction longitudinal et transverse).