The development of a new class of alternative plastics has been encouraged in the past few years due to the serious environmental issues, such as toxicity and carbon dioxide emissions. Hence, the introduction of renewable, biodegradable, and biocompatible materials is becoming critical as substituents of conventional synthetic plastics. To design a new system of novel TEMPO-oxidized cellulose nanofibrils (TOCNs)/graphene oxide (GO) composite, the 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation was utilized to disintegrate never-dried wood nanofibrillated cellulose (NFC). GO was incorporated through high intensity homogenization and ultrasonication with varying degree of oxidation (0.5X, 1X, and 2X) of NFC and GO percent loadings: 0.4, 1.2, and 2.0wt %. As a result, despite the presence of carboxylate groups and graphene oxide (GO), X-ray diffraction (XRD) test showed the crystallinity of the bio-nanocomposite was not altered. Scanning electron microscopy (SEM) was used to characterize their morphologies. In addition, the thermal stability of TOCN/GO composite decreased upon oxidation level, and dynamic mechanical analysis (DMA) signified strong intermolecular interactions with the improvement in Young's storage modulus, and tensile strength. Fourier transform infrared spectroscopy (FTIR) was employed to see the hydrogen bonds between GO and cellulosic polymer matrix. The oxygen transmission rate (OTR) of TOCN/GO composite decreased. The water vapor permeability (WVP) was not significantly affected by the reinforcement with GO, but the moderate oxidation enhanced the barrier properties. Ultimately, the newly fabricated TOCN/GO composite can be utilized in a wide range of life science applications, such as food and medical industries. / Master of Science / In recent years, petroleum-based polyolefins have been contributing to severe environmental issues. With this in perspective, the development of a new class of alternative plastics has been encouraged. Hence, the introduction of renewable, biodegradable, and biocompatible materials is becoming critical as a substitute for non-degradable synthetic plastics. In this study, a new system of novel cellulose-based plastic composites was designed by incorporating carbon nanofillers at various percent loadings and different degree of surface modification of the plastics. These treatments are the economical way to achieve the targeted properties for industrial applications, exhibiting the obvious improvement in tensile strength due to the strong interaction between nanofillers and cellulose. In addition, water vapor and oxygen barrier properties play significant roles in food packaging since food decay is vulnerable to these two factors. The barrier performance was enhanced by hindering the permeation of oxygen gases, whereas the water vapor permeability was not significantly affected by the reinforcement with carbon nanofillers. Ultimately, the newly fabricated cellulose plastic can be utilized in various applications, especially, such as the pharmaceutical and biomedical areas, packaging for food and goods, and agriculture due to their high availability, sustainability, and biodegradability.

Au cours de ce travail de thèse, la Cellulose Nanofibrillée (CNF) a été isolée à partir de fibres de paille d’avoine puis modifiée chimiquement par des alcoxysilanes en milieu aqueux. La CNF silylée a ensuite été utilisée pour élaborer de nouveaux matériaux composites et mousses biosourcés.Le chapitre I présente quelques aspects généraux concernant les nanocelluloses, en particulier la NFC et ses applications dans le domaine des matériaux composites et des mousses.Le chapitre II est consacré à la fonctionnalisation de la CNF par le méthyltriméthoxysilane - choisi comme alcoxysilane modèle - ainsi qu’à la caractérisation du matériau silylé. Plusieurs paramètres réactionnels (pH, temps de réaction, concentration initiale en silane) ont été étudiés et optimisés, à partir de deux protocoles expérimentaux distincts. Les modifications ont été caractérisées à l’échelle moléculaire par différentes techniques physico-chimiques. Les propriétés des nanofibrilles silylées, comme la morphologie, cristallinité, mouillabilité, hygro-copicité et stabilité thermique, ont ensuite été évaluées.Dans le chapitre III, l’impact de la silylation sur les propriétés mécaniques et hygroscopiques de composites à matrice acide poly(lactique) ou matrice polydiméthylsiloxane chargés en NFC a été évalué.Pour finir, l’impact de la silylation sur les propriétés de mousses élaborées à partir de NFC lyophilisées a été étudié dans le chapitre IV (porosité, propriétés en compression, conductivité thermique, mouillabilité, hygroscopicité et oléophilicité). / In this thesis, nanofibrillated cellulse (NFC) has been isolated from oat straw and chemically modified by alkoxysilanes in water medium. Silylated NFC has been subsequently used to elaborate novel biobased composite materials and foamsChapter I presents some general aspects about nanocelluloses – in particular Nanofibrillated Cellulose (NFC) - and their use in composite materials and foams.Chapter II is dedicated to the functionalization of NFC by methyltrimethoxysilane - chosen as a model silane - and to the comprehensive examination of the silylated material. Reaction conditions such as pH, reaction time and initial silane concentration have been particularly in-vestigated and optimized using two distinct experimental protocols. The modifications have been characterized at the molecular level by various physicochemical techniques. The proper-ties of the silylated nanofibrils i.e. the morphology, crystallinity, wettability, hygroscopicity and thermal stability, have been subsequently examined. Chapter III investigates the impact of silylation on the mechanical and hygroscopic properties of NFC-reinforced composites prepared with two distinct polymeric matrices: poly(lactic acid) (PLA) and polydimethylsiloxane (PDMS).Chapter IV examines the impact of silylation on the properties of NFC-foams prepared by freeze drying, in particular on the porosity, compressive properties, thermal conductivity, wet-tability, hygroscopicity and oleophilicity.

Ce projet vise à développer un nouveau procédé de fabrication de nanofibrilles de cellulose (NFC) à fort taux de matière sèche et en consommant peu d’énergie. L’extrusion bi-vis, technique industrielle, efficace énergétiquement et facilement adaptable fut ainsi utilisée pour produire des NFC à 20%. En diminuant considérablement la teneur en eau, cette nouvelle stratégie permet de diminuer le coût du transport, d’améliorer le stockage et d’élargir leur domaine d’application. Ce travail a consisté (i) à développer de nouveaux prétraitements chimiques des fibres de celluloses, respectueux de l’environnement pour faciliter la fibrillation de la cellulose et produire des NFC fonctionnelles de qualité, (ii) à optimiser les conditions d’extrusion ainsi que le profil de vis et (iii) à préparer des matériaux à partir de cette nouvelle matière. Quatre prétraitements chimiques ont été identifiés comme facilement industrialisables et ensuite optimisés. La nanofibrillation par extrusion a été ensuite simulée par un logiciel pour obtenir des conditions d’extrusion optimisées. La production de NFC de qualité à l’échelle semi-industrielle a été validée. Différentes applications ont été envisagées pour ces nouvelles NFC à fort taux de matière sèche. / This project aims at developing a new process to produce high solid content cellulose nanofibrils (CNF) decreasing the energy consumption and preserving the high quality compared to classic processes. Twin screw extrusion (TSE), industrially well-known, energy efficient and highly adaptable technique, was optimized to produce CNF at 20 wt% solid content. By decreasing considerably the water content, this new strategy improves the transport cost, the storage and widening the field of application and formulation. The objectives were to (i) develop new green pretreatments of cellulose fibers to facilitate the fibrillation and produce high quality functionalized CNF, (ii) optimize TSE screw profile and conditions to produce CNF and (iii) prepare new materials made of this new type of CNF. Four chemical pretreatments of cellulose fibers have been identified as industrially feasible, leading to high quality functionalized CNF and were widely studied and optimized. The nanofibrillation by TSE was simulated using a simulation software and TSE conditions were then successfully optimized. This cost-effective approach was validated at semi-industrial scale. Finally, different new applications with this new grade of CNF were considered.

As nonoceluloses são partículas com pelo menos uma dimensão menor que 100 nm. A produção delas a partir de materiais lignocelulósicos tem obtido grande destaque nos últimos anos. A celulose nanocristalina (CNC) é tradicionalmente produzida através da hidrólise ácida, utilizando alta concentração de ácido, grande volume de água e com baixo rendimento. A celulose nanofibrilada (CNF) é produzida pela desfibrilação mecânica de polpas celulósicas com alto consumo de energia. Por outro lado, embora a produção industrial de etanol 2G já tenha começado, com as primeiras plantas de produção em escala espalhadas pelo mundo, a hidrólise enzimática completa da celulose para este fim não é economicamente viável e gera um resíduo rico em celulose e altamente recalcitrante, que poderia ser utilizado para produzir nanoceluloses, que tem alto valor agregado. Neste contexto, este estudo investigou a viabilidade técnica da produção das nanoceluloses (CNC e CNF) integradas ao processo de produção de açúcares fermentescíveis para a produção de etanol 2G a partir do bagaço de cana-de-açúcar. Incialmente, em uma planta piloto de produção de etanol 2G, o bagaço foi pré-tratado por explosão a vapor, que gerou a celulignina que foi deslignificada com NaOH. A polpa celulósica gerada foi tratada com peróxido de hidrogênio em meio alcalino para realizar a remoção da lignina residual. Os materiais gerados pelo pré-tratamento e pelo processo de polpação em meio alcalino foram caracterizados quando sua composição química e hidrolisados com diferentes cargas de enzimas. Os resultados mostraram a eficiência dos pré-tratamentos aplicados ao bagaço de cana-de-açúcar causando o enriquecimento em celulose e a diminuição do teor lignina e de hemiceluloses, acarretando um maior acesso das enzimas a celulose. O estudo do efeito das cargas enzimáticas, do aumento da carga de sólidos e do sistema de agitação, resultou em conversões de celulose em torno de 80%, atingindo concentrações acima de 120 g/L. Utilizando o resíduo de hidrólise da polpa celulósica, foram obtidas as nanoceluloses. A CNC apresentou tamanho médio de partículas de 679 nm, índice de cristalinidade de 54%, diâmetros mais frequentes entre 55 e 65 nm e rendimento de aproximadamente 48%. A CNF apresentou tamanho médio de 722 nm e diâmetros com maior frequência em torno de 60 nm, e rendimento de aproximadamente 38%. As suspensões aquosas de CNC e CNF apresentaram baixa estabilidade, quando monitoradas através do potencial zeta. / Nanocelluloses are particles with at least one dimension smaller than 100 nm. Their production from lignocellulosic materials has gained prominence in recent years. Cellulose nanocrystals (CNC) is traditionally produced through acid hydrolysis using high acid concentration, high water volume and results in low yield. Cellulose nanofibrils (CNF) is produced by mechanical defibrillation of cellulosic pulps with high energy consumption. On the other hand, despite the fact the production of 2G ethanol has already reached commercial production, with the first commercial facilities around the worldwide, complete enzymatic hydrolysis of cellulose for this purpose is not economically viable and generates a highly recalcitrant residue rich in cellulose and, which could be used to produce nanocelluloses, high-added value products. In this context, this study investigated the technical viability of obtaining nanocelluloses integrated into the production process of fermentable sugars to obtain 2G ethanol from sugarcane bagasse. Initially, at a pilot plant for production of2G ethanol, sugarcane bagasse was pre-treated by steam explosion, generating cellulignin, which was delignified with NaOH. The resulting cellulosic pulp was treated with hydrogen peroxide in an alkaline medium to remove residual lignin. The materials generated after the pre-treatment and the pulping process in alkaline medium were characterized regarding their chemical composition and then hydrolyzed with different loads of enzymes. The results showed that the pre-treatments applied to the bagasse caused the enrichment in cellulose and the decrease of lignin and hemicelluloses contents, leading to a greater access of the enzymes to cellulose. The enzymatic charges used in the experiments, which were evaluated in combination with the increase of the solids loading together with the change of the agitation system, resulted in a cellulose conversion of around 80%, reaching concentrations above 120 g/L. Using the hydrolysis residue of the cellulosic pulp, nanocelluloses were obtained. The CNC showed a mean particle size of 679 nm, crystallinity index of 54%, diameters between 55 and 65 nm and a yield of about 48%. The CNF displayed an average particle size of 722 nm and diameters with higher frequency around 60 nm. The aqueous suspensions of CNC and CNF showed low stability when monitored through the zeta potential.

Nanocellulose has received considerable interest during the last decade because it is renewable and biodegradable, and has excellent mechanical properties, nanoscale dimensions and wide functionalization possibilities. It is considered to be a unique and versatile platform on which new functional materials can be based. This thesis focuses on nanocellulose from wood (NFC) and from Cladophora algae (CNC), functionalized with surface charges or coated with the conducting polymer polypyrrole (PPy), aiming to study the influence of synthesis processes on structural and electrochemical properties of such materials and assess their biocompatibility. The most important results of the work demonstrated that 1) CNC was oxidized to the same extent using electrochemical TEMPO-mediated oxidation as with conventional TEMPO processes, which may facilitate easier reuse of the reaction medium; 2) NFC and CNC films with or without surface charges were non-cytotoxic as assessed by indirect in vitro testing. Anionic TEMPO-CNC films promoted fibroblast adhesion and proliferation in direct in vitro cytocompatibility testing, possibly due to its aligned fibril structure; 3) Rinsing of PPy-coated nanocellulose fibrils, which after drying into free-standing porous composites are applicable for energy storage and electrochemically controlled ion extraction, significantly degraded the PPy coating, unless acidic rinsing was employed. Only minor degradation was observed during long-term ambient storage; 4) Variations in the drying method as well as type and amount of nanocellulose offered ways of tailoring the porosities of nanocellulose/PPy composites between 30% and 98%, with increments of ~10%. Supercritical CO2-drying generated composites with the largest specific surface area yet reported for nanocellulose/conducting polymer composites (246 m2/g). The electrochemical oxidation rate was found to be controlled by the composite porosity; 5) In blood compatibility assessments for potential hemodialysis applications, heparinization of CNC/PPy composites was required to obtain thrombogenic properties comparable to commercial hemodialysis membranes. The pro-inflammatory characteristics of non-heparinized and heparinized composites were, to some extent, superior to commercial membranes. The heparin coating did not affect the solute extraction capacity of the composite. The presented results are deemed to be useful for tuning the properties of systems based on the studied materials in e.g. energy storage, ion exchange and biomaterial applications.

Nanofibrillated cellulose (NFC) from wood is an interesting material constituent of high strength and high aspect ratio, which easily forms networks through interfibril secondary bonding including hydrogen bonds. This has been exploited in preparation of new materials, which extend the range of properties for existing cellulosic materials. The objective is to explore processing-structure and structure-property relationships in NFC materials. Dense networks of NFC, referred to as “nanopaper” having a random-in-the-plane orientation of the fibrils have been successfully prepared by a papermaking-like process involving vacuum filtration and water evaporation using laboratory papermaking equipment. Large, flat and transparent nanopaper sheets have thus been prepared in a relatively short time. Using the same preparation route, NFC was used to reinforce pulped wood fibers in dense network structures. NFC networks formed in the pore space of the wood fiber network give an interesting hierarchical structure of reduced porosity. These NFC/wood fiber biocomposites have greater strength, greater stiffness and greater strain-to-failure than reference networks of wood fibers only. In particular, the work to fracture (area under the stress-strain curve) is doubled with an NFC content of only 2%. The papermaking preparation route was extended to prepare nanocomposites of high NFC content with a cellulose derivative matrix (hydroxyethyl cellulose, HEC) strongly associated to the NFC. Little HEC was lost during filtration. The NFC/HEC composites have high work to fracture, higher than that of any reported cellulose composite. This is related to NFC network characteristics, and HEC properties and its nanoscale distribution and association with NFC. Higher porosity NFC nanopaper networks of high specific surface area were prepared by new routes including supercritical drying, tert-butanol freeze-drying and CO2 evaporation. Light-weight porous nanopaper materials resulted with mechanical properties similar to thermoplastics but with a much lower density and a specific surface area of up to 480 m2/g. Freeze-drying of hydrocolloidal NFC dispersions was used to prepare ultra-high porosity foam structures. The NFC foams have a cellular foam structure of mixed open/closed cells and “nanopaper” cell wall. Control of density and mechanical properties was possible by variation of NFC concentration in the dispersion. A cellulose I foam of the highest porosity ever reported (99.5%) was prepared. The NFC foams have high ductility and toughness and may be of interest for applications involving mechanical energy absorption. Freeze-drying of NFC suspended in tert-butanol gave highly porous NFC network aerogels with a large surface area. The mechanical behavior was significantly different from NFC foams of similar density due to differences in deformation mechanisms for NFC nanofiber networks. / QC 20110406

In the past decade there has been increasing interest in exploring the use of nanocellulose in medicine. However, the influence of the physicochemical properties of nanocellulose on the material´s biocompatibility has not been fully investigated.  In this thesis, thin films of nanocellulose from wood (NFC) and from Cladophora algae (CC) were modified by the addition of charged groups on their surfaces and the influence of these modifications on the material´s physicochemical properties and on cell responses in vitro was studied. The results indicate that the introduction of charged groups on the surface of NFC and CC results in films with decreased surface area, smaller average pore size and a more compact structure compared with the films of unmodified nanocelluloses. Furthermore, the fibres in the carboxyl-modified CC films were uniquely aggregated and aligned, a state which tended to become more prevalent with increased surface-group density. The biocompatibility studies showed that NFC films containing hydroxypropyltrime-thylammonium (HPTMA) groups presented a more cytocompatible surface than unmodified NFC and carboxymethylated NFC regarding human dermal fibroblasts. Carboxymethyl groups resulted in NFC films that promoted inflammation, while HPTMA groups had a passivating effect in terms of inflammatory response.  On the other hand, both modified CC films behaved as inert materials in terms of the inflammatory response of monocytes/macrophages and, under pro-inflammatory stimuli, they suppressed secretion of the pro-inflammatory cytokine TNF-α, with the effects of the carboxylated CC film more pronounced than those of the HPTMA CC material.  Carboxyl CC films showed good cytocompatibility with fibroblasts and osteoblastic cells. However, it was necessary to reach a threshold value in carboxyl-group density to obtain CC films with cytocompatibility comparable to that of commercial tissue culture material.  The studies presented here highlight the ability of the nanocellulose films to modulate cell behaviour and provide a foundation for the design of nanocellulose-based materials that trigger specific cell responses. The bioactivity of nanocellulose may be optimized by careful tuning of the surface properties. The outcomes of this thesis are foreseen to contribute to our fundamental understanding of the biointerface phenomena between cells and nanocellulose as well as to enable engineering of bioinert, bioactive, and bioadaptive materials.

Research of new sustainable and low cost materials, such as cellulose, is of high interest. Modifications of the cellulose can be performed in order to create a “smart” material which responds to external stimuli, such as variations in pH and temperature, by changing its properties. This “smart” behavior is observed in some polymers, however, for certain applications they exhibit poor mechanical properties. These polymers can be bound by physical adsorption to cellulose, both in macro and nano scale, creating an improved “smart” composite material. In this project, thermoresponsive block-copolymers with different lengths of poly (diethylene glycol) methacrylate (PDEGMA) and poly N-(2-dimethylamino ethyl) methacrylate (PDMAEMA) in only one length, PDMAEMA-b-PDEGMA, were synthesized employing atom transfer radical polymerization (ATRP). 1H-NMR, SEC and DLS were used to characterize the block-copolymers. UV-Vis spectroscopy was employed to confirm the thermo-responsive behavior of the charged and uncharged block-copolymers, being lower for the higher molecular weight ones due to the higher polymer-polymer interactions. In a second step, PDMAEMA was charged positively by quaternization of its amine group with ICH3. Polyelectrolyte titration was used to determine the total number of charges in the quaternized block-copolymers. In addition, TEMPO-oxidized nanofibrillated cellulose (NFC) was produced by procedures found in literature. Finally, adsorption of the cationic block-copolymers onto the anionic NFC in tris base at pH 8.3 was performed and purified by consecutive filtrations, creating a novel smart composite material with different PDEGMA lengths in the block-copolymer. FT-IR confirmed that the block-copolymers were successfully adsorbed to the NFC. TGA results showed a higher thermal stability for the composite than for the TEMPO-NFC and quaternized block-copolymers. The block-copolymer modified NFC exhibited thermoresponsive behavior with LCST’s ranging from 30 to 44 °C, from higher to lower molecular weights, respectively.  Adsorption of polyelectrolytes in modified cellulose could be a promising way to create smart improved materials in further research.

Sporopollenin is considered a resistant material and might be applicable in flame retardant material. The use of renewable material in fields mainly dominated by toxic materials, such as bromides in flame retardant materials, could greatly improve the sustainability in those fields. A renewable porous film could be of interest in applications were cellophane is used today. The aim of this report is to investigate some basic properties of films made from nanofibrillated cellulose (NFC) and Lycopodium spores with a specific focus on flame retardant and mechanical properties. These properties were investigated using machines such as SEM, a universal electromechanical tester, TGA and vertical flame testing. During the production of the films an ultra turrax, rotavapor and rapid köthen was used. The films containing spores did not improved properties such as flame retardancy and mechanical properties when compared to the original NFC film. Density was lowered by almost half in some cases compared to the original NFC-film. Mechanical properties of the alkali-treated spores showed a significant increase compared to the untreated spores. An increased spore-ratio shows a decreased Young’s modulus. Further research on flame retardancy could be done using xyloglucan or another more flame retardant organic compound as a matrix. A foaming agent inside the sporopollenin could also contribute to flame retardancy. The mechanical properties could be compared to cellophane in order to see any future possibility of application. If possible pure sporopollenin should be used instead of whole spores. / Degree Project in Polymeric Materials, First Cycle

Globalization and centralization have resulted in prolonged transportation time between producer and consumer, and thus put more demand on the perseveration of a product for longer duration and protect it from oxidation. The presence of oxygen in packages severely foreshortens the storage life as it yield losses of nutrients and allow microbial growth, which can cause changes in smell, taste as well as discoloration. Earlier food and beverage containers were made in inorganic materials e.g. metal and glass, however lately more and more focus have been on synthetic organic materials as these show several advantages, e.g. weight. However, still today most of the commercial packaging materials, organic or inorganic, are not considered to be environmental friendly. Thus, efforts have to be made today in order to invent alternative materials that can make the society of tomorrow more sustainable. Cellulose is the most abundant biopolymer in the world, hence making it desirable to use in “green” packaging applications. Furthermore, cellulose has proven being able to form films with great gas barrier potential under specific conditions. However, cellulose based materials are sensitive to moisture with severely increased oxygen transmission with increased relative humidity as a result; hence it is desired to make cellulose less hygroscopic by chemical modification. First, nanofibrillated cellulose (NFC) with 720 mmol carboxylic groups/g fiber was produced by oxidation of dissolving pulp before homogenization. Thereafter a polymer was synthesized utilizing Initiator A as an initiator at T1 and T2. The polymer synthesized at T1 yielded a polymer with a viscosity average molecular weight of 5770 g/mol.  The polymer was then grafted on the oxidized NFC through a coupling reaction performed in Buffer C using Coupling agent A. The grafting procedure was performed in Buffer C at ambient conditions giving rise to a material composed of 33 wt% synthetic polymer and 67 wt% NFC. The coupling was conducted several times in order to investigate how the final product can be affected by varying reactant feed and dispersion method. Finally, films of NFC and NFC-g-Polymer were manufactured by vacuum filtration from a 0.05 wt% Solvent A dispersion and were evaluated with field emission scanning electron microscopy.