In this project, nanocomposite films and coatings, based on renewable resources, were prepared. A hemicellulose biopolymer, based on xylan, was used as the matrix, and cellulose nanowhiskers (CNWs), as the functional additive. The xylan based matrix is an oxygen, grease and aroma barrier, making it a suitable raw material for packaging applications. Cellulose nanowhiskers were used to improve the mechanical properties and thermal stability of the hemicellulose while improving the barrier properties at high relative humidity. The focus of this thesis was processing and characterization of xylan based nanocomposites’ films and coatings. Two grades of xylans, A and B, and food contact approved plasticizer were used to prepare homogeneous films and coatings of nanocomposites, containing 2.5, 5 and 10 wt% of CNWs. The microscopy study showed no aggregations of CNWs in micro scale. Crosslinking was efficiently performed on A films and coatings, and a crosslinking density of about 70% was obtained. X-ray diffraction studies revealed a semicrystalline structure for A matrices and an amorphous one for B. The addition of CNWs resulted in an increase of crystallinity in both A and B samples. Dynamic mechanical thermal analysis showed that addition of whiskers tended to increase the storage modulus at high temperature (90°C) region. Furthermore, crosslinking as well as small amounts of whiskers (2.5 to 5 wt%) resulted in a shift of tan δ peak of nanocomposites to higher temperatures. Mechanical testing revealed a trend of improved mechanical stability in nanocomposites with small amounts of whiskers, whereas the Young’s modulus, maximum strain and maximum stress increased. However, the mechanical properties decreased at 10 wt% CNW content, probably due to aggregation of whiskers. Moreover, barrier tests, like crisp bag, grease permeability and especially oxygen permeability, indicated improved barrier properties of the materials at moist conditions. In general, improvements in barrier and mechanical performance of the material were observed, resulting from combination of CNW addition and crosslinking. / <p>Validerat; 20111121 (anonymous)</p>

Au niveau académique et industriel, les nanocelluloses connaissent un engouement toujours grandissant. Ce projet de thèse explore la modification chimique des nanofibrilles de cellulose (CNF) pour des applications médicales. Des drogues et prodrogues de principes actifs (PA) ont été liées de manière covalente ou adsorbées sur des films ou des suspensions de CNF. Pour l’immobilisation covalente, une première stratégie d’estérification en milieu aqueux a été utilisée sur des films de CNF. Les propriétés antibactériennes contre des bactéries à gram positif et à gram négatif, ainsi que l’activité par contact prolongée de ces films, ont été démontrés. La seconde stratégie a porté sur la modification des suspensions de CNF au travers d’une procédure multi-étape (amidation puis chimie click), à nouveau en phase aqueuse. Des outils de caractérisation innovants comme la résonance magnétique nucléaire (RMN) dopée par polarisation dynamique nucléaire (PDN), ont permis de compléter les techniques classiques pour prouver le succès du greffage chimique. L’adsorption de PA sur les films et suspensions de CNF a été menée en parallèle de l’immobilisation covalente. Ensuite, les films de CNF avec des PA greffés ou adsorbés ont été utilisés pour développer des dispositifs médicaux pour application cutanée. Quant aux suspensions de CNF avec PA greffé ou adsorbé, elles ont été intégrées à des matrices de collagène pour créer de nouveaux prototypes de réparation pariétale. Leur activité antibactérienne et leurs propriétés de relargage contrôlé confirment l’intérêt de ces composites pour le design de dispositifs médicaux innovants.Mot-clés: nanocellulose, nanofibrilles de cellulose, fonctionnalisation, dispositif médical, activité antibactérienne, relargage contrôlé / In line with the ever-increasing academic and industrial interest for wood derived nanocellulose, the present work investigated the chemical surface modification of cellulose nanofibrils (CNFs) for biomedical application. Drugs and pro-drugs of active principle ingredients (APIs) were covalently immobilized or adsorbed onto CNFs films or suspensions. For covalent immobilization, the first strategy selected calls for water-based and single step esterification of CNF films. The resulting materials demonstrated antibacterial activity against both gram-positive and gram-negative bacterial strains, with a prolonged contact-active effect. In the second strategy, CNFs suspensions were modified through a multistep reaction, involving amidation and click chemistry, still water-based. Highly innovative characterization tools, such as dynamic nuclear polarization (DNP) enhanced nuclear magnetic resonance (NMR), complemented well-established techniques to confirm the success of grafting. In parallel to covalent immobilization, an adsorption strategy was also adopted, on both CNFs films and suspensions. Then, the CNF films with grafted or adsorbed APIs were used for preparing 100% CNF medical devices for topical applications. Another component of this work used CNF suspensions with grafted or adsorbed APIs were embedded in collagen matrices to prepare model medical device of soft tissue repair implants. Antibacterial activity against both aerobic and anaerobic bacteria, together with controlled release properties were assessed confirming that such composites present the expected active properties, and can be used for the design of innovative medical devices.Key words: nanocellulose, cellulose nanofibrils, functionalization, medical devices, antibacterial activity, drug release

L'auteur n'a pas fourni de résumé de moins de 4000 caractères en français / L'auteur n'a pas fourni de résumé de moins de 4000 caractères en anglais

Nature creates high performance materials under modest conditions, i.e., neutral pH and ambient temperature and pressure. One of the most significant materials is the plant cell wall. The plant cell wall is a composite of oriented cellulose microfibrils reinforcing a lignin/hemicellulose matrix. In principle, the plant cell wall composite is designed much like a synthetic fiber-reinforced polymer composite. Unlike synthetic composites, the plant cell wall has an excellent combination of high modulus, strength, toughness and low density that originates in the optimal interactions between the biopolymers. Therefore, to produce high performance composites, a unique route may be to mimic a biological system like the plant cell wall. The present work focuses on understanding the thermodynamics of biopolymer assembly to exploit the process in vitro. In our system, we use an already polymerized nanocellulose template and polymerize phenolic monomers on the template using a peroxidase enzyme. In the first part, we have polymerized phenol using horseradish peroxidase (HRP) in the presence of TEMPO-oxidized nanocellulose. Similar to native plant cell wall structures, the polyphenol-nanocellulose composite had intimate mixing of polyphenol and cellulose at the nanoscale with the presence of cellulose promoting a uniquely organized structure. The obtained composite material showed synergy that enhanced the thermal stability, hydrophobicity, and possibly mechanical properties. In the second part, monolignol coniferyl alcohol was polymerized in the presence of nanocellulose by the same procedure. A comparison between the polyphenol composite and poly(coniferyl alcohol) (PCA) composite revealed that the propanyl substitution imparted flexibility to the PCA molecules so that they could bend and form a hollow globule structure to envelope nanocellulose inside. Polyphenol could not do this because of its rigidity. / Master of Science

Nanocellulose has gained lots of attentions in recent years due to the development of nanotechnology. Thousands of publications have been reported about the fabrication, characterization and application of nanocellulose, among which most of the nanocelluloses were fabricated from the microcrystalline cellulose (MCC) or pulp, and only two methods about the nanocellulose fabrication have been reported, i.e. sulphuric acid hydrolysis and mechanical treatment. The sulphuric acid method can only obtain low yield of nanocellulose and the mechanical treatment can not fabricate nanocellulose with high crystallinity index (CI) and well separation. These problems limit the scale up of nanocellulose to industrial area. Moreover, none of works has reported the application of nanocellulose for the modification of natural fibres and only a few works reported the reinforcement of epoxy with nanocellulose. In this this research, we fabricated nanocellulose directly from hemp fibres by employing oxidation/sonication method with the aim to solve the main problems of nanocellulose fabrication with sulphuric acid hydrolysis or mechanical. By using this method the yield of nanocellulose could up to 54.11 % and the crystallinity of nanocellulose was 86.59 %. In order to expand the application of nanocellulose, we investigated the modification of natural fibres (hemp) with nanocellulose and the fabrication of nanocomposite. Two-step modification, i.e. dodecyltrimethylammonium bromide (DTAB) pretreatment and nanocellulose modification, was used to modify hemp fibres. In this process, we systematically investigated the deformation of hemp fibres, revealed the mechanism of deformation on the mechanical property of single fibre by using Fourier transform infrared spectroscopy (FTIR) and investigated the effect of deformation on the hemp fibre modification with nanocellulose by using energy dispersive X-ray (EDX). The two-step modification increased the mechanical properties of hemp fibres significantly. Compared with raw hemp fibres, the modulus, tensile stress and tensile strain of the two-step nanocellulose modified hemp fibres increase by 36.13 %, 72.80 % and 67.89 %, respectively. Moreover, two-step modification facilitated the improvement of interfacial property of fibres. This novel natural fibre modification provides new clue to exploit nanocellulose as a green chemical agent for natural fibres modification. We modified nanocellulose by using curing agent of epoxy---diethylenetriamine (DETA). This modification could increase the dispersity of nanocellulose in epoxy and reinforce epoxy. Compared with epoxy, the modulus, tensile stress and tensile strain of the modified nanocellulose/epoxy nanocomposite increased 1.42 %, 15.44 % and 27.47 %, respectively.

Yes / Cementitious composites, the most abundant human-made materials in the world, are challenged to be more sustainable, durable and cost-effective to adapt to the development of structural engineering, economy and environment. Owing to their excellent strength, toughness and durability, nano-fillers reinforced cementitious materials have attracted broad attention in civil engineering researches and applications. However, it is worth noting that nano-fillers reinforced cementitious materials achieve their proprieties by using of different industrial nano-fillers, i.e., graphenes, carbon nanotubes, carbon nanofibers, etc. Although the properties of conventional cementitious materials are improved, the incorporation of the above nano-fillers are high cost and environmental footprint. Different from high-energy consuming carbon nanofillers, nanocellulose is one of the biomass-derived nanofillers with excellent nanometer properties, biological performances and composite effects, and it has proved to be a promising green filler to enhance the mechanical properties, durability and functional properties and lower the carbon footprint of cementitious composites. Therefore, this paper provides an overview on biomass-derived nanocellulose modified cementitious composites, mainly focusing on their fabrication, properties (early performance, mechanical performance, durability, and functional performance) and applications. It also concludes with an outline of some future opportunities and challenges in the development of biomass-derived nanocellulose modified cementitious composites.

Le projet de thèse a permis de proposer des stratégies "verte" pour la modification chimique de nanofibrilles de cellulose (CNF) afin de leur conférer des propriétés antimicrobiennes. Sept différentes CNF fonctionnalisées ont été produites en tenant compte des principes de développement durable et de la faisabilité industrielle dans le domaine des emballages de nouvelles générations. Dans un premier temps, les CNF ont été fonctionnalisées avec de la cyclodextrine pour contrôler le relargage de molécules actives. Dans d'autres stratégies, des surfaces antimicrobiennes par contact ont été préparées en greffant des molécules naturelles ou en suivant les principes de biomimétisme. Les résultats sont très prometteurs et permettent l'obtention de surface clairement antimicrobienne sans relargage de molécules. Des caractérisations de grandes qualités ont confirmé ces greffages (par exemple, XPS, RMN, QCM-D) ainsi que les propriétés antimicrobiennes (par rapport à la S.aureus ou E.Coli). Une des meilleurs stratégies utilisant des CNF greffées avec des antibiotiques, a été produites à l'échelle laboratoire mais aussi implémentée à l'échelle semi-industrielle, avec pour objectif final la production d'emballages médicaux limitant les maladies nosocomiales. / The present investigation has developed efficient green strategies for the chemical modification of cellulose nanofibers (CNF), in order to impart antimicrobial activities. Seven different functionalized CNF was produced in this context keeping in mind sustainability and industrial feasibility within new generation packaging field. First, CNF was designed with cyclodextrin to control the release of natural active molecules. In other strategies, non-leaching contact active antimicrobial surfaces were prepared using natural active molecules or following biomimetic approaches. Results are very promising and allow obtaining efficient antimicrobial surface without any release. High level characterizations confirm surface grafting (e.g. XPS, QCM-D, NMR) and anti-microbial efficiency (S.aureus, E.Coli). One of the best strategies using antibiotic grafted CNF was produced at lab scale but also implemented at semi industrial scale. The final idea was to produce medical packages limiting the cross contamination in hospitals.

Ce projet vise à développer de nouvelles encres à base de nanofils d’argent et de nanocellulose pour des applications conductrices et transparentes. Les nanocelluloses, nanoparticules issues de la cellulose, sont de deux types : les nanocristaux de cellulose (NCC) et les nanofibrilles de cellulose (NFC) et possèdent des propriétés bien spécifiques. Ce travail a consisté d’une part (i) à utiliser la forme tubulaire et rigide des NCC pour produire des nanotubes d’argents par synthèse chimique, avant leur formulation en encre et d’autre part (ii) à utiliser les propriétés d’enchevêtrement des NFC flexibles pour stabiliser des nanofils d’argent commerciaux, habituellement instables en suspension. Les divers résultats de ce projet ont permis d’aboutir à la formulation brevetée et à la commercialisation d’une encre conductrice à base d’une faible quantité d’argent et de NCC et de deux encres conductrices et transparentes à base de NFC et de nanofils d’argent. Les interactions physico-chimiques et la stabilité colloïdale de ces suspensions hybrides ont été étudiée de manière fondamentale, tout en développant des formulations adaptées à divers procédés d’impression, que ce soit à échelle laboratoire mais aussi industrielle. / This project aims at developing new conductive inks based on nanocellulose and silver nanowires for transparent and conductive applications. Nanocellulose are nanoparticles extracted from the cellulose and two kinds currently exist: the cellulose nanocrystals (CNC) and the cellulose nanofibrils (CNF). This project have evaluated on one hand the ability of using tubular rigid CNC as template for producing silver nanorods, prior their formulation into conductive inks. On the other hand, the ability of using flexible and entangled CNF to stabilize commercial silver nanowires, usually unstable in suspension, was investigated. The results of this project lead to the patented formulation and commercialization of one low silver content conductive ink based on silver and CNC and two conductive transparent ink based on CNF and silver nanowires. Physico-chemical interactions and colloidal stability of such hybrid suspension have been scientifically studied meanwhile printing process adapted formulation have been successfully designed and tested at laboratory scale but also industrial scale.

L’originalité de ce travail est d’étudier la contribution des nanocelluloses pour lafonctionnalisation des papiers spéciaux. Il y a deux types de nanocellulose, les nanocristauxde cellulose (NCCs) et les microfibrilles de cellulose (MFCs). Il en résulte des propriétésdifférentes à l’état de suspension et à l’état sec. La propriété des MFCs de former un réseaud’enchevêtrement est utilisée pour la dispersion des particules. L’auto-assemblage des NCCsa permis d’élaborer des films iridescents. Ces films ont été considérés comme couchesmodèles puis ensuite mis en oeuvre dans le procédé de fabrication des papiers. Il a été proposéavec succès d’utiliser les MFCs dans le couchage pour réduire la quantité de pigmentsopacifiants pour les papiers minces, et de fabriquer des pigments iridescents pour obtenir despropriétés d’anti-contrefaçon. Ces approches ont été validées à l’échelle laboratoire mais aussipilote. / The original feature of this work is to investigate the contribution of two families ofnanocellulose for their application within specialty papers. It exists two families ofnanocellulose, i.e. Cellulose Nanocrystals (CNCs) and Cellulose Nanofibers (CNFs). It resultsin different properties in suspension and solid states. CNFs with their ability to formentangled network are used as dispersive network for particles. In contrast, the self-assemblyproperties of CNC are used to obtain iridescent films. First, the films based on nanocellulosewere considered as model layers. Then, results were implemented at the industrial scalewithin the papermaking process. It is proposed to use CNF based coating for savingopacifying pigments in lightweight paper, and manufacturing iridescent pigment to impartanti-counterfeiting properties. These sustainable and cost-effective approaches were thenvalidated at pilot scale.

Ce projet s’est focalisé sur l’ajout de nouvelles propriétés à des papiers grâce à l’utilisation de nanocelluloses fonctionnelles. Ces nanocelluloses sont des nanoparticules extraites du bois qui peuvent être divisées en deux catégories : les nanofibrilles de cellulose (CNFs) et les nanocristaux de cellulose (CNCs). Ce travail s’est essentiellement penché sur l’utilisation des CNFs. Leur réactivité chimique a été utilisée afin de les fonctionnaliser avec des organotrialkoxysilanes. C’est aussi leur fort enchevêtrement ainsi que la grande viscosité de ces CNFs en suspension qui ont été utilisés afin de synthétiser des petites particules de silsesquioxane pour rendre le matériau final antimicrobien et (super)hydrophobe. Les connaissances obtenues à travers l’étude sur des films modèle de CNFs ont ensuite été appliquées au couchage du papier. Ces CNFs fonctionnelles ont donc été évaluées pour le développement d’un papier possédant une surface antimicrobienne, anti-adhérente, barrière aux graisses ou superhydrophobe. / The aim of this work is to implement new properties to a paper based material via the use of functional nanocelluloses. Nanocelluloses are nanoparticles extracted from wood and distinguished in two categories: Cellulose Nanofibrils (CNFs) and Cellulose Nanocrystals (CNCs). This work has only been carried out with CNFs. The chemical reactivity of CNFs was used to functionalize them with organotrialkoxysilanes. The entangled network and highly viscous suspension of CNFs was also used to synthesize silsesquioxane particles with limited size to impart (super)hydrophobic and antimicrobial properties. Knowledge obtained through the study of model CNFs films was then applied to paper based material coating. The functional CNFs were evaluated for its use in an antimicrobial, anti-adherent, greaseproof or superhydrophobic paper surface.