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Nanofibrillated cellulose (NFC) was used as bio-based stabilizing agent in the heterophase polymerization of methyl methacrylate (MMA) to nanoscale poly(methyl methacrylate) (PMMA) spheres. NFC/MMA suspensions at different NFC/MMA ratios were prepared in water, and the suspension stability was evaluated before the subsequent polymerization. The resulting polymerization products as well as products from several control experiments were analyzed via optical microscopy, SEM, and isolation experiments associated with thermogravimetric analysis. PMMA spheres had diameters in the range of 150–250 nm and were regularly distributed within the NFC network, whereas NFC acted as a stabilizer during the polymerization. The appearance of the resulting PMMA spheres within the NFC network was influenced by different factors, such as the reaction conditions, the initiator, and the solubility of the monomer., Colloid and Polymer Science, 294 (9), ISSN:0303-402X, ISSN:1435-1536

International audience; A novel and straightforward method for the surface acetylation of cellulose nanowhiskers by transesterification of vinyl acetate is proposed. The reaction of vinyl acetate with the hydroxyl groups of cellulose nanowhiskers obtained from cotton linters was examined with potassium carbonate as catalyst. Results indicate that during the first stage of the reaction, only the surface of the nanowhiskers was modified, while their dimensions and crystallinity remained unchanged. With increasing reaction time, diffusion mechanisms controlled the rate, leading to nanowhiskers with higher levels of acetylation, smaller dimensions, and lower crystallinity. In THF, a solvent of low polarity, the suspensions from modified nanowhiskers showed improved stability with increased acetylation.

The present invention relates to reinforced composite hydrogel based on a polymer blend and comprising a network of fibres, said polymer blend comprising UV sensitive molecules. It also relates to a process for preparing the reinforced composite hydrogel according to the invention.

The swelling and compressive mechanical behavior as well as the morphology and biocompatibility of composite hydrogels based on Tween® 20 trimethacrylate (T3), N-vinyl-2-pyrrolidone (NVP) and nanofibrillated cellulose (NFC) were assessed in the present study. The chemical structure of T3 was verified by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance, and the degree of substitution was found to be around 3. Swelling ratios of neat hydrogels composed of different concentrations of T3 and NVP were found to range from 1.5 to 5.7 with decreasing concentration of T3. Various concentrations of cellulose nanofibrils (0.2-1.6wt.%) were then used to produce composite hydrogels that showed lower swelling ratios than neat ones for a given T3 concentration. Neat and composite hydrogels exhibited a typical nonlinear response under compression. All composite hydrogels showed an increase in elastic modulus compared to neat hydrogel of about 3- to 8-fold, reaching 18kPa at 0% strain and 62kPa at 20% strain for the hydrogel with the highest NFC content. All hydrogels presented a porous and homogeneous structure, with interconnected pore cells of around 100nm in diameter. The hydrogels are biocompatible. The results of this study demonstrate that composite hydrogels reinforced with NFC may be viable as nucleus pulposus implants due to their adequate swelling ratio, which may restore the annulus fibrosus loading, and their increased mechanical properties, which could possibly restore the height of the intervertebral discs.

Cellulose nanofibrils (CNF) are steadily gaining attention since this material is a renewable alternative to artificial polymers. Moreover, waste products from cellulose-based industries (e.g. paper mills) or from agricultura can be used as raw material for CNF isolation. However, the up-scaling from the laboratory to the industry can only be achieved if the energy costs are low enough to compete against low-price petroleum derivatives. The objective of this work is to present an energy-related study of the direct fibrillation of cellulose-based materials using a grinding process. Two waste materials, namely wheat straw and recycled newspaper, have been investigated as starting materials, together with bleached Wood pulp for comparison purposes. The mechanical properties and specific surface áreas of the resulting fibrillated materials are then presented and systematically compared with each other. The properties of the bleached wood-pulp fibres exhibited the highest values that were reached already at low energy inputs. The different properties of CNF isolated out the waste materials could reach values close to their máxima for energy inputs as low as about 5 kWh/kg compared to the ca. 10kWh/kg needed with high pressure homogenization.

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., 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).