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Nanocellulose was extracted from short bast fibers, from hemp ( Cannabis sativa L.) plants harvested at seed maturity, non-retted, and mechanically decorticated in a defibering apparatus, giving non-aligned fibers. A chemical pretreatment with NaOH and HCl allowed the removal of most of the non-cellulosic components of the fibers. No bleaching was performed. The chemically pretreated fibers were then refined in a beater and treated with a cellulase enzyme, followed by mechanical defibrillation in an ultrafine friction grinder. The fibers were characterized by microscopy, infrared spectroscopy, thermogravimetric analysis and X-ray diffraction after each step of the process to understand the evolution of their morphology and composition. The obtained nanocellulose suspension was composed of short nanofibrils with widths of 5-12 nm, stacks of nanofibrils with widths of 20-200 nm, and some larger fibers. The crystallinity index was found to increase from 74% for the raw fibers to 80% for the nanocellulose. The nanocellulose retained a yellowish color, indicating the presence of some residual lignin. The properties of the nanopaper prepared with the hemp nanocellulose were similar to those of nanopapers prepared with wood pulp-derived rod-like nanofibrils.

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 chemistry principles. The presence of the drug is confirmed by several characterization tools and methods such as Raman spectroscopy, elemental analysis, Dynamic Nuclear Polarization enhanced NMR. This technique allows enhancing the sensitivity of NMR 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., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The aim of this work was to study the cellulose fibers deconstruction by twin-screw extrusion with in situ enzymatic hydrolysis via bioextrusion, for cellulose nanofibrils (CNF) production. Cellulose pulp was extruded with an optimized screw profile, with or without (reference) the addition of an enzymatic solution. An increase of crystallinity index from 67.0% to 73.7% and decrease of DP from 1003 to 419 were observed with bioextrusion. Direct activity measurements of the enzyme confirmed its activity during the process (sugar content increasing from 0.07 ± 0.004 to 2.38 ± 0.003 mg/mL) and after the process (specific activities around 0.20 CMCU/mL). Enzymes were not deactivated during bioextrusion and could be recycled. CNF properties were higher with bioextrusion compared to reference (respective quality indices of 55.5 ± 2.7 and 39.8 ± 2.8), with a lower energy consumption. This proof of concept could be optimized for the industrial production of highly concentrated CNF., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2020. Published by Elsevier Ltd.)

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 CO 2 eq/kg, while all impacts of cellulosic fiber-based materials are below 1.5 kg CO 2 eq/kg., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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/m 2  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., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

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., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

An active ink composed of cellulose nanofibrils and silver nanowires was deposited on flexible and transparent polymer films using the bar coating process, achieving controlled thicknesses ranging from 200 nm up to 2 μm. For 350 nm thick coating on polyethylene terephthalate films, high transparency (75.6% transmittance) and strong reduction of bacterial growth equal to 89.3% and 100% was noted respectively against Gram-negative Escherichia Coli and Gram-positive Staphylococcus Aureus bacteria using AATCC contact active standard test. Retained antibacterial activity was found with films produced by reverse gravure roll-to-roll process, showing the promising capability of this antibacterial solution to be deployed industrially. Finally, the same ink was also deposited on polylactic acid substrate to investigate barrier properties: for 350 nm thick coating, a reduction of 49% of oxygen transmission rate (dry conditions) and 47% reduction of water vapor transmission rate was noted, proving the enhanced barrier properties of the coatings., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study investigates the adsorption of a block copolymer composed of a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) cationic polyelectrolyte and a poly(di(ethylene glycol) methyl ethermethacrylate) (PDEGMA) on oxidized cellulose nanocrystals (TO-CNCs) to produce hydrogels. PDMEAMA- b-PDEGMA was synthesized by atom-transfer radical polymerization. The extent and dynamics of the adsorption of PDMAEMA- b-PDEGMA on TO-CNCs were determined by electromechanical microbalance and optical techniques. Electrostatic adsorption was identified on TO-CNCs with the quaternized block copolymer. Small-angle neutron scattering experiments were performed to investigate the polymer behavior on the TO-CNC surfaces. Depending on the temperature, block copolymer induces the aggregation of nanocrystals after adsorption by connecting CNCs bundles with block copolymer chains. A reversible liquid-to-gel transition, triggered by temperature, was clearly detected by rheological measurements for the copolymer-CNC mixtures. At the optimal copolymer to CNC ratio the viscosity increased by 4 orders of magnitude at low shear rates. These stimuli-responsive CNC-based materials could be used as injectable biomedical systems.

Thin cellulose nanofiber (CNF) nanostructured substrates with varying roughness, stiffness (Young's modulus), porosity, and swelling properties were produced by varying the conditions used during fabrication. It was shown that with increased heat exposure, CNF substrate porosity in an aqueous state decreased while Young's modulus in a water submerged state increased. In this study, the adhesion and viability of mesenchymal stem cells (MSCs) cultured on this CNF substrate will be presented. Viability of D1/BALBc MSCs were assessed for 24 and 48 h, and it was shown that depending on the CNF substrate the viability varied significantly. The adhesion of MSCs after 6 and 24 h was conditional on material mechanical properties and porosity of the CNF in cell culture conditions. These results suggest that material properties of CNF nanostructured substrate within the aqueous state can be easily tuned with curing step without any chemical modification to the CNF and that these changes can affect MSC viability in cell culture.

Recent focus on the preparation of antimicrobial surfaces using cellulose nanofibers (CNF) has gained considerable attention. In this work, functionalization of CNF films in 100% aqueous solution with three different aminosilanes, including 3-aminopropyl trimethoxysilane (APMS), 2-aminoethyl 3-aminopropyl trimethoxysilane (DAMS)and 3-2-(2-aminoethylamino) ethylamino propyl-trimethoxysilane (TAMS) is reported for the fabrication of contact active antimicrobial materials. Grafted CNF films were comprehensively characterized by FTIR, TGA, contact angle, elemental analysis, solid-state 29 Si NMR, FEG-SEM and SEM-EDX. It was found that all the silanes were grafted on the surface of nanofibers without any change in the morphology or fibril structure through different grafting efficiency, depending on the aminoalkyl chain length. The effect of variable aminoalkyl length and initial grafting concentration was analyzed against gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) by qualitative and quantitative standards. The most promising results were obtained with 3-2-(2-aminoethylamino) ethylamino propyl-trimethoxysilane at very low concentration which completely restrict bacterial growth after 24h with Gram-positive bacteria. This study, for the first time, established the relationship between the aminoalkyl chain length and its corresponding antibacterial activity., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Current investigations deal with new surface functionalization strategy of nanocrystalline cellulose-based substrates to impart active molecule release properties. In this study, cellulose nanocrystals (CNC) were surface-functionalized with β-cyclodextrin (β-CD) using succinic acid (SA) and fumaric acid (FA) as bridging agents. The main objective of this surface modification performed only in aqueous media was to obtain new active materials able to release antibacterial molecules over a prolonged period of time. The reactions were conducted by immersing the CNC film into a solution composed of β-CD, SA and FA, leading to CNC grafting. The materials were characterized by infrared spectroscopy (FT-IR), Quartz crystal microbalance-dissipation (QCM-D), AFM and phenolphthalein (PhP) was used to determine the efficiency of CNC grafting with β-CD. The results indicated that β-CD was successfully attached to the CNC backbone through the formation of ester bonds. Furthermore, carvacrol was entrapped by the attached β-CD and a prolonged release was confirmed. In particular, CNC grafted to β-CD in the presence of FA was selected as the best solution. The antibacterial activity and the controlled release were studied for this sample. Considerably longer bacterial activity against B. subtilis was observed for CNC grafted to β-CD compared to CNC and CNC-FA, confirming the promising impact of the present strategy., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this study, a composite film based on TEMPO-oxidized cellulose nanofibers (TOCN), polyvinyl alcohol (PVA) and polypyrrole (PPy) was synthesized in situ by a chemical polymerization, resulting in the induced absorption of PPy on the surface of the TOCN. The composite films were investigated with scanning electron microscopy, thermogravimetric analysis, contact angle measurements, mechanical tests, and evaluation of antibacterial properties. The developed composite has nearly identical Young modulus (3.4GPa), elongation (2.6%) and tensile stress (about 51MPa) to TOCN even if PPy, which as poor properties by itself, was incorporated. From the energy-dispersive X-ray spectroscopy (EDX) results, it was shown that PPy is mainly located on the composite surface. Results confirmed by an increase from 54.5 to 83° in contact angle, an increased heat protection (Thermogravimetric analysis) and a decrease in surface energy. The nanocomposites were also evaluated for antibacterial activity against bacteria occasionally found in food: Gram-positive Bacillus subtilis (B. subtilis) and Gram-negative bacteria Escherichia coli (E. coli). The results indicate that the nanocomposites are effective against all of the bacteria studied as shown by the decrease of 5.2logcolonyformingunits (CFU) for B. subtilis and 6.5logCFU for E. coli. Resulting in the total destruction of the studied bacteria. The perfect match between the resulting inhibition zone and the composite surface area has demonstrated that our composite was contact active with a slight leaching of PPy. Our composite was successful as an active packaging on meat (liver) as bacteria were killed by contact, thereby preventing the spread of possible diseases. While it has not been tested on bacteria found in medicine, TOCN/PVA-PPy film may be able to act as an active sterile packaging for surgical instruments., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Cellulose nanofibers (CNFs) were recently investigated for the elaboration of new functional food-packaging materials. Their nanoporous network was especially of interest for controlling the release of active species. Qualitative release studies were conducted, but quantification of the diffusion phenomenon observed when the active species are released from and through CNF coating has not yet been studied. Therefore, this work aims to model CNF-coated paper substrates as controlled release system for food-packaging using release data obtained for two model molecules, namely caffeine and chlorhexidine digluconate. The applied mathematical model - derived from Fickian diffusion - was validated for caffeine only. When the active species chemically interacts with the release device, another model is required as a non-predominantly diffusion-controlled release was observed. From caffeine modeling data, a theoretical active food-packaging material was designed. The use of CNFs as barrier coating was proved to be the ideal material configuration that best meets specifications., (Copyright © 2016. Published by Elsevier Ltd.)

Improving thermal stability of TEMPO-oxidized cellulose nanofibrils (TOCNs) is a major challenge for the development and preparation of new nanocomposites. However, thermal degradation of TOCNs occurs at 220 °C. The present study reports a simple way to improve thermal stability of TOCNs by the heat-induced conversion of ionic bonds to amide bonds. Coupling amine-terminated polyethylene glycol to the TOCNs is performed through ionic bond formation. Films are produced from the dispersions by the casting method. Infrared spectroscopy and thermogravimetric analysis confirm conversion of ionic bonds to amide bonds for the modified TOCN samples after heating. As a result, improvement of TOCNs' thermal stability by up to 90 °C is successfully achieved., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Surface functionalization of cellulose nanocrystals (CNCs) aims to improve their properties. The main objective of this study was the esterification of the surface of CNCs using nontoxic resin acids, rosin. The structural and morphological modifications of CNC nanorods were characterized by (13)C NMR and Fourier transform infrared spectroscopy, atomic force microscopy, and X-ray diffraction analyses. The properties of functionalized CNCs were evaluated by thermogravimetric analysis and contact-angle measurements. The results indicate that the esterification proceeded from the surface of the CNC. The antimicrobial activities of the modified and neat CNC were investigated; the rosin-grafted CNC exhibited a strong antibacterial activity against Gram-negative bacteria and a modest antibacterial activity against Gram-positive bacteria., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Cellulose nanocrystals (CNC) and starch nanocrystals (SNC) were grafted by ozone-initiated free-radical polymerisation of styrene in a heterogeneous medium. Surface functionalisation was confirmed by infrared spectroscopy, contact angle measurements, and thermogravimetric and elemental analysis. X-ray diffraction and scanning electron microscopy showed that there was no significant change in the morphology or crystallinity of the nanoparticles following ozonolysis. The grafting efficiency, quantified by (13)C NMR, was greater for SNC, with a styrene/anhydroglucose ratio of 1.56 compared to 0.25 for CNC. The thermal stability improved by 100°C. The contact angles were 97° and 78° following the SNC and CNC grafting, respectively, demonstrating the efficiency of the grafting in changing the surface properties even at low levels of surface substitution. The grafting increased the compatibility with the polylactide, and produced nanocomposites with improved water vapour barrier properties. Ozone-mediated grafting is thus a promising approach for surface functionalisation of polysaccharide nanocrystals., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In the last decade, a new fiber pretreatment has been proposed to make easy cellulose fibrillation into microfibrils. In this context, different surface cationized MFC was prepared by optimizing the experimental parameters for cellulose fibers pretreatment before fibrillation. All MFCs were characterized by conductometric titration to establish degree of substitution, field emission gun scanning electron microscopy (FEG-SEM), atomic force microscopy (AFM) and optical microscopy assessed the effect of pretreatment on the morphology of the ensuing MFCs. Antibacterial activities of neat and cationized MFC samples were investigated against Gram positive bacteria (Bacillus subtilis, Staphylococcus aureus) and Gram negative bacteria (Escherichia coli). The CATMFC sample at DS greater than 0.18 displayed promising results with antibacterial properties without any leaching of quaternary ammonium into the environment. This work proved the potential of cationic MFCs with specific DS for contact active antimicrobial surface applications in active food packaging, medical packaging or in health and cosmetic field., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Contact active surfaces are an innovative tool for developing antibacterial products. Here, the microfibrillated cellulose (MFC) surface was modified with the β-lactam antibiotic benzyl penicillin in aqueous medium to prepare antimicrobial films. Penicillin was grafted on the MFC surface using a suspension of these nanofilaments or directly on films. Films prepared from the penicillin-modified MFC were characterized by Fourier transform infrared spectroscopy, contact angle measurements, elemental analysis, and X-ray photoelectron spectroscopy and tested for antibacterial activity against the Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Penicillin-grafted MFC films exhibited successful killing effect on Gram-positive bacteria with 3.5-log reduction whereas bacteriostatic efficiency was found in penicillin-grafted MFC suspension. The zone of inhibition test and leaching dynamic assay demonstrated that penicillin was not diffused into the surrounding media, thus proving that the films were indeed contact active. Thus, penicillin can be chemically bound to the modified substrate surface to produce promising nonleaching antimicrobial systems.

A simple method to produce biobased iridescent pigments from cellulose nanocrystal (CNC) films is reported. The process consists of forming nanostructured films from a CNC liquid-crystalline suspension and an appropriate dry grinding. The features of the iridescent pigments are described; they have a flake-like morphology with a thickness of 25 μm. However, because of the presence of sulfate groups, thermal degradation and high redispersion in water occur, which affect the iridescent property of these biobased pigments. To overcome such limitations, two post-treatments are proposed. The sulfate ester groups are removed from the iridescent pigments with vacuum overdrying. The mass loss of iridescent pigment in water is reduced with an increase of the ionic strength in the aqueous medium by NaCl addition. These post-treatments have proven to be efficient and engineered pigments based on CNC films can be used to add anticounterfeiting features to packaging manufactured by classical paper techniques or extrusion., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

An environmentally friendly and simple method, named SolReact, has been developed for a solvent-free esterification of cellulose nanocrystals (CNC) surface by using two nontoxic carboxylic acids (CA), phenylacetic acid and hydrocinnamic acid. In this process, the carboxylic acids do not only act as grafting agent, but also as solvent media above their melting point. Key is the in situ solvent exchange by water evaporation driving the esterification reaction without drying the CNC. Atomic force microscopy and X-ray diffraction analyses showed no significant change in the CNC dimensions and crystallinity index after this green process. The presence of the grafted carboxylic was characterized by analysis of the "bulk" CNC with elemental analysis, infrared spectroscopy, and (13)C NMR. The ability to tune the surface properties of grafted nanocrystals (CNC-g-CA) was evaluated by X-ray photoelectron spectroscopy analysis. The hydrophobicity behavior of the functionalized CNC was studied through the water contact-angle measurements and vapor adsorption. The functionalization of these bionanoparticles may offer applications in composite manufacturing, where these nanoparticles have limited dispersibility in hydrophobic polymer matrices and as nanoadsorbers due to the presence of phenolic groups attached on the surface.

Nanofibrillated cellulose (NFC) and their derivatives were prepared using three chemical surface modification strategies. All grafting was characterized by FTIR and contact angle measurements in order to evaluate the efficiency of grafting. Antibacterial activities of neat and grafted samples were investigated against two kinds of bacteria (i.e. Gram+ (Staphylococcus aureus) and Gram- (Klebsiella pneumoniae)). All the grafted samples displayed promising results with at least bacteriostatic effect or bactericidal properties. They also strongly enhanced the photo-catalytic antimicrobial effect of TiO2. This study proves that it is better to use grafted NFC either alone or for functionalization with TiO2 if anti-bacterial properties are desired. The cellulose backbone is known to be easily biodegradable in different biodegradation conditions and environments. The chemical surface modifications applied on NFC in the present work did not negatively influence this valuable property of cellulose but help for monitoring this property, which could be very useful for paper, packaging and composites., (Copyright © 2014 Elsevier B.V. All rights reserved.)

This study aims to develop a high-performance delivery system using microfibrillated cellulose (MFC)-coated papers as a controlled release system combined with the well-known drug delivery agent, β-cyclodextrin (βCD). Chlorhexidine digluconate (CHX), an antibacterial molecule, was mixed with a suspension of MFC or a βCD solution or mixed with both the substances, before coating onto a cellulosic substrate. The intermittent diffusion of CHX (i.e., diffusion interrupted by the renewal of the release medium periodically) was conducted in an aqueous medium, and the release mechanism of CHX was elucidated by field emission gun-scanning electron microscopy, SEM, NMR, and Fourier transform infrared analyses. According to the literature, both βCD and MFC are efficient controlled delivery systems. This study indicated that βCD releases CHX more gradually and over a longer period of time compared to MFC, which is mainly due to the ability of βCD to form an inclusion complex with CHX. Furthermore from the release study, a complementary action when the two compounds were combined was deduced. MFC mainly affected the burst effect, while βCD primarily controlled the amount of CHX released over time. In this paper, two different types of controlled release systems are proposed and compared. Depending on the final application, the use of βCD alone would release low amounts of active molecules over time (slow delivery), whereas the combination of β-cyclodextrin and MFC would be more suitable for the release of higher amounts of active molecules over time (rapid delivery)., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The crystallization, mechanical and biodegradation properties of poly(lactic acid)/natural rubber/cellulose nanocrystals (CNC) bionanocomposites were evaluated. Three types of CNC were used in this study, one unmodified (CNC), long alkyl chain grafted CNC (C18-g-CNC) and PLA grafted CNC (PLA-g-CNC). The CNC modifications determined the affinity of the nanocrystals toward the polymers and reflected on the ultimate properties. Interestingly, PLA-g-CNC acted as a nucleating agent for the PLA matrix in the bio-based PLA/NR blend. Good mechanical properties were reported, as the bionanocomposites maintained a high elongation at break for a concentration up to 3 wt.% of cellulose nanocrystals. Moreover, the disintegration study confirmed that the materials completely disintegrated after one month in compost., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

PLA/NR/cellulose nanowhisker composites were prepared using three types of cellulose nanocrystals (CNC), i.e. unmodified CNC obtained from acid hydrolysis of microcrystalline cellulose and two surface modified CNC. The two modification reactions, consisting on the grafting of long alkyl chains and of PLA chains onto the cellulose nanocrystals were carried out in order to facilitate the incorporation of the nanocrystals in the PLA/NR blend. A novel processing method was optimized combining solvent casting and extrusion in order to obtain a homogeneous dispersion of the nanofillers in the blend. The CNC modifications determined their location in the PLA/NR blend and influenced its morphology., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Cellulose nanocrystals have been prepared by acid hydrolysis of Luffa cylindrica fibers. The acid-resistant residue consisted of rod-like nanoparticles with an average length an diameter around 242 and 5.2nm, respectively (aspect ratio around 46). These cellulose nanocrystals have been used as a reinforcing phase for the processing of bio-nanocomposites using polycaprolactone (PCL) as matrix. To promote interfacial filler/matrix interactions the surface of cellulose nanocrystals was chemically modified with n-octadecyl isocyanate (C(18)H(37)NCO). Evidence of the grafting was supported by infrared spectroscopy and elemental analysis. X-ray diffraction analysis was used to confirm the integrity of cellulose nanocrystals after chemical modification. Both unmodified and chemically modified nanocrystals were used to prepare nanocomposites. The thermal properties of these materials were determined from differential scanning calorimetry and their mechanical behavior was evaluated in both the linear and non-linear range., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The present study reports for the first time a method to obtain water redispersible dried NFC using freeze-drying. No chemical surface modification was required to get this kind of product. Salt addition (sodium chloride: NaCl) strategy has been selected to block and then to regenerate hydrogen bonds during the drying and the redispersion steps, respectively. Several samples were produced at different pH (i.e., 4, 6, 8, and 10). All the redispersed NFC were characterized by different techniques (e.g., FE-SEM, XRD, EPMA-EDX) to check the effect of salt on NFC aggregation. The interactions between NFC and NaCl at different pH conditions have been discussed and the rheology of the redispersed NFC suspension has been performed. All the results prove a perfect water redispersion at pH 8 and exactly similar suspension is obtained after water dispersion of dried NFC following our procedure. These results are very promising for increasing application of NFC.

Interest in microfibrillated cellulose (MFC) has been increasing exponentially. During the last decade, this bio-based nanomaterial was essentially used in nanocomposites for its reinforcement property. Its nano-scale dimensions and its ability to form a strong entangled nanoporous network, however, have encouraged the emergence of new high-value applications. In previous years, its mode of production has completely changed, as many forms of optimization have been developed. New sources, new mechanical processes, and new pre- and post-treatments are currently under development to reduce the high energy consumption and produce new types of MFC materials on an industrial scale. The nanoscale characterization possibilities of different MFC materials are thus increasing intensively. Therefore, it is critical to review such MFC materials and their properties. Moreover, very recent studies have proved the significant barrier properties of MFC. Hence, it is proposed to focus on the barrier properties of MFC used in films, in nanocomposites, or in paper coating., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Cellulose nanocrystals (or whiskers) and microfibrillated cellulose (MFC) were successfully obtained from sisal fibers and modified with n-octadecyl isocyanate (C(18)H(37)NCO) using two different methods with one innovation that consists of an in situ solvent exchange procedure. The surface chemical modification was characterized by elemental analysis, as well as FTIR and XPS spectroscopies. The crystalline structure of both unmodified and modified nanoparticles was investigated through X-ray diffraction measurements. It was shown that the efficiency of the chemical modification is strongly dependent on the nature of the nanoparticle with explanation linked to specific area, ability of peeling, and solvent dispersion. The surface chemical modification with n-octadecyl isocyanate allows dispersion of the nanoparticles in organic solvents and may allow processing of nanocomposite films from a casting/evaporation technique for a broad range of polymeric matrices.

In the present work, nanowhiskers and microfibrillated cellulose (MFC) both extracted from sisal were used to reinforce polycaprolactone (PCL). We report the influence of the nanoparticle's nature on the mechanical and thermal properties of the ensuing nanocomposites. The surface of both the nanoparticles was chemically modified to improve their compatibilization with the polymeric matrix. N-Octadecyl isocyanate (C18H37NCO) was used as the grafting agent. PCL nanocomposite films reinforced with sisal whiskers or MFC (raw or chemically modified) were prepared by film casting. The thermal behavior (Tg, Tm, Tc, and degree of crystallinity) and the mechanical properties of the nanocomposites in both the linear and the nonlinear range were determined using differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA), and tensile tests, respectively. Significant differences were reported according to the nature of the nanoparticle and amount of nanofillers used as reinforcement. It was also proved that the chemical treatment clearly improves the ultimate properties of the nanocomposites.

The biocompatibility and very high specific area of cellulose nanofibrils (CNF) are properties of high interest for the development of active substrates for new medical device development. Enzyme pretreated CNF (CNF-e) can be self-organized into nanostructured membranes that are suitable for active principle ingredients (API) encapsulation through adsorption phenomena. In addition, tunable surface chemistry of CNF-e, allow for covalent immobilization of API. In this work, ciprofloxacin is integrated to CNF-e membranes according to two different strategies. The first one relies only on adsorption mechanisms; ciprofloxacin is encapsulated in the bulk before the membrane formation by solvent casting. The influence of the membrane properties and preparation parameters such as grammage, thickness and drying technique, are assessed with water uptake measurements and API release experiments. The second strategy deals with the covalent immobilization of ciprofloxacin directly onto CNF-e membrane. The two kinds of membranes are then compared in terms of antibacterial activity, in both static and dynamic conditions. Thick CNF-e membranes loaded with adsorbed ciprofloxacin that were overdried (2 h, 150 °C) prove to be more resistant in liquid medium and present a more prolonged drug release. However, these membranes rapidly lost their antibacterial activity, while CNF-e membranes with covalently immobilized ciprofloxacin remain contact active for several days. These 100% CNF active nanostructured membranes can be used as new wound dressing for topical application. [ABSTRACT FROM AUTHOR]

A novel type of acetylated cellulose nanofibre (CNF) was extracted successfully from sisal fibres using chemical methods. Initially, a strong alkali treatment was used to swell the fibres, followed by a bleaching step to remove the residual lignin and finally an acetylation step to reduce the impact of the intermolecular hydrogen bonds in the nanocellulose. The result of this sequence of up-scalable chemical treatments was a pulp consisting mainly of micro-sized fibres, which allowed simpler handling through filtration and purification steps and permitted the isolation of an intermediate product with a high solids content. An aqueous dispersion of CNF could be obtained directly from this intermediate pulp by simple magnetic stirring. As a proof of concept, the dispersion was used directly for preparing a highly translucent CNF film, illustrating that there are no large aggregates in the prepared CNF dispersion. Finally, CNF films with alkali extracts were also prepared, resulting in flatter films with an increased mass yield and improved mechanical strength. [ABSTRACT FROM AUTHOR]