Filtration and separation technologies remain as one of the biggest challenges humanity currently faces. The separation of different elements such as bacteria, viruses, heavy metals, particles, and chemical agents require the development of multifunctional membranes. In membrane technology, one of the most promising fabrication techniques is electrospinning, which can produce highly tailored non-woven fibrous multifunctional membranes with a high surface area. On the other hand, cellulose derivatives, like cellulose acetate, have many beneficial properties for filtering technology such as high availability and easy functionalization. Likewise, cellulose nanocrystals are used to improve mechanical properties and functionalize membranes. In this project, a cellulose nanocrystal (CNCs) functionalized cellulose acetate electrospun multifunctional membrane is developed for adsorption and separation of nanosized particles. In this work, cellulose acetate (CA) fibers with an average fiber diameter of approximately 900 nm were electrospun and tested as membranes for size and affinity based filtration. First, the electrospinning process was optimized regarding solution and process parameters. As a result, solution parameters were found to be 12 wt% solid content CA dissolved in a 1:1 acetone:acetic acid solution. Regarding process parameters, the suitable electrospinning parameters were found to be 18 kV applied voltage, a feeding rate of 5 mL/h, and a tip-to-collector distance of 20 cm.   The electrospun CA membrane was coated with cationic (+) and anionic (-) cellulose nanocrystals up to a 25 wt% concentration. The incorporation of CNCs, of either anionic or cationic surface charge, affected membrane wettability. The neat CA membrane had a hydrophobic behavior with a contact angle of 110°. The addition of CNCs decrease contact angle, to 31.5° for CA-CNCs(-) and 50° for CA-CNCs(+), which resulted in functionalized membranes with a hydrophilic behavior. Both functionalized membranes managed to maintain high flux values. CA-CNCs(-) maintained a flux of 9500 Lm−2h−1, while CA-CNCs(+) maintained a flux of 6700 Lm−2h−1. The addition of cellulose nanocrystals improved the mechanical properties of the CA membranes. The tensile strength increases from 410 kPa to 4990 kPa for CA-CNCs(-) membranes and 3010 MPa for CA-CNCs(+) membranes, and is accompanied by an increase in Young’s modulus as well. To evaluate the adsorption efficiency and size-exclusion filtration, an anionic dye (Congo red), a cationic dye (Victoria blue), and 500 nm model particles were used. CA-CNC(-) membranes achieved a removal efficiency of 96% of 500 nm particles with an affinity-based dye removal of 63% of Victoria blue dye. On the other hand, CA-CNC(+) membranes achieved a removal efficiency of 43% of 500 nm particles with a dye removal of 27% of Congo red dye. In this regard, CA-CNC(-) membranes were the best candidate for size-exclusion filtration, while also maintaining a good level of adsorption. Cellulose based composite membranes were successfully produced as multifunctional filters that could act in both size-exclusion regime and affinity-based regime. A cellulose acetate fibrous membrane was produced by electrospinning, tuning for fiber size and porosity, while the incorporation of cellulose nanocrystals functionalizes the membranes and enhance mechanical properties, and wettability.

Tesis por compendio / [EN] The current PhD thesis deals with the development and characterization of novel nanocomposites based on biodegradable poly(mannitol sebacate) (PMS) matrices with tailored properties and shape-memory capabilities for biomedical applications. Two types of fillers -cellulose nanocrystals (CNC) and electrospun poly(lactic acid) nanofibers (NF-PLA)- were used as reinforcement in order to induce and/or enhance the shape-memory properties of PMS matrices. Also, different crosslinking profiles and stoichiometric ratios between mannitol and sebacic acid (1:1 and 1:2) were studied and evaluated to obtain samples with low and high degrees of crosslinking. An appropriate combination of the crosslinking profile and the monomer ratio for PMS matrix, as well as the addition of low content of CNC, allowed the development of PMS/CNC nanocomposites with a wide range of mechanical properties and degradation profiles. On the other hand, highly oriented poly(lactic acid) (PLA) nanofiber mats obtained by electrospinning were embedded in the PMS matrices. An enhancement of up to 53-fold in the Young's modulus was observed for PMS/NF-PLA nanocomposites filled with 15 wt% of PLA nanofibers. The incorporation of fillers (CNC and NF-PLA) allowed the development of thermally active shape-memory nanocomposites with an enhancement of parameters such as recovery stress and shape fixity. The electrospun PLA-reinforced nanocomposites, offered the best balance of mechanical and thermal properties, as well as a greater control of the transition temperature for switching the change of shape, within a useful range of temperatures. Owing to that, these materials may be of interest as smart responsive systems in long-term biomedical applications. / [ES] La presente tesis doctoral, se centra en el desarrollo y caracterización de nuevos nanocompuestos biodegradables, a partir de matrices de poli(mannitol sebacato) (PMS) con propiedades a medida y capacidades de memoria de forma para aplicaciones biomédicas. Dos tipos de cargas -nanocristales de celulosa (CNC) y nanofibras de ácido poliláctico (NF-PLA) obtenidas mediante electrospinning- se han utilizado como refuerzo, con la finalidad de inducir y/o mejorar las propiedades de memoria de forma en matrices de PMS. Se han estudiado y evaluado diferentes tratamientos de curado y ratios de reacción entre el mannitol y ácido sebácico (1:1 y 1:2), con la finalidad de obtener muestras con bajo y alto grado de reticulación. Una combinación adecuada del tratamiento de curado y el ratio entre monómeros del PMS, así como la adición de bajos contenidos de CNC, permitió desarrollar nanocompuestos de PMS/CNC con un amplio rango de propiedades mecánicas y perfiles de degradación. Por otro lado, se han producido mats de nanofibras de ácido poliláctico (PLA) con alta orientación mediante la técnica de electrospinning, para embeberse en matrices de PMS, observándose una mejora de hasta 53 veces en el módulo de Young para nanocompuestos de PMS/NF-PLA con un 15% en peso de nanofibras. La incorporación de cargas (CNC y NF-PLA) permitió el desarrollo de nanocompuestos con memoria de forma activada térmicamente, con una mejora de parámetros tales como la fuerza de recuperación y la capacidad de fijación. Los nanocompuestos reforzados con NF-PLA obtenidas por electrospinning, ofrecieron el mejor balance de propiedades mecánicas y térmicas, así como un mayor control de la temperatura de transición para la activación del cambio de forma en un intervalo útil de temperaturas. Por todo ello, estos materiales pueden resultar de interés como sistemas activos en aplicaciones biomédicas de larga duración. / [CA] La present tesi doctoral se centra en el desenvolupament i caracterització de nous nanocompostos biodegradables a partir de matrius de poli(mannitol sebacato) (PMS) amb propietats a mesura i capacitats de memòria de forma per a aplicacions biomèdiques. Dos tipus de càrregues -nanocristals de cel·lulosa (CNC) i nanofibres d'àcid polilàctic (NF-PLA) obtingudes mitjançant electrospinning- s'han utilitzat com a reforç amb la finalitat d'induir i/o millorar les propietats de memòria de forma en matrius de PMS. S'han estudiat i avaluat diferents tractaments de curat i ràtios de reacció entre el mannitol i àcid sebàcic (1:1 i 1:2) amb la finalitat d'obtenir mostres amb baix i alt grau de reticulació. Una combinació adequada del tractament de curat i el ràtio entre monòmers del PMS, així com l'addició de baixos continguts de CNC, va permetre desenvolupar nanocompostos de PMS/CNC amb un ampli rang de propietats mecàniques i perfils de degradació. D'altra banda, s'han produït mats de nanofibres d'àcid polilàctic (PLA) amb alta orientació mitjançant la tècnica de electrospinning, per embeure's en matrius de PMS, observant-se una millora de fins a 53 vegades en el mòdul de Young per nanocompostos de PMS/NF-PLA amb un 15% en pes de nanofibres. La incorporació de càrregues (CNC i NF-PLA) va permetre el desenvolupament de nanocompostos amb memòria de forma activada tèrmicament, amb una millora de paràmetres tals com la força de recuperació i la capacitat de fixació. Els nanocompostos reforçats amb NF-PLA obtingudes per electrospinning, van oferir el millor balanç de propietats mecàniques i tèrmiques, així com un major control de la temperatura de transició per a l'activació del canvi de forma en un interval útil de temperatures. Per tot això, aquests materials poden resultar d'interés com a sistemes actius en aplicacions biomèdiques de llarga durada. / Sonseca Olalla, A. (2015). DEVELOPMENT OF SHAPE-MEMORY COMPOSITES BASED ON A BIODEGRADABLE POLYESTER ELASTOMER [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/54129 / Compendio

Cellulose Nanocrystals have been used in a wide range of applications including cement composites as a strength enhancer. This work analyses the use of CNC from several sources and production methods, and their effects on rheology and hydration of pastes made using different cement types with different compositions. Cement Types I/II and V were used to prepare pastes with different water to cement ratios (w/c) and measure the changes in rheology upon CNC addition. The presence of tricalcium aluminate (cement chemistry denotes as C3A) made a difference in the magnitude of CNC effects. At dosages under 0.5vol% to dry cement, CNC reduced the yield stress up to 50% the control value. Pastes with more C¡A reduced yield stress over a wider range of CNC dosages. CNC also increased yield stress of pastes with dosages above 0.5%, twice the control value for pastes with high C3A content at 1.5% CNC and up to 20 times for pastes without C3A at the same dosage.<br>All the CNCs used were characterized in length, aspect ratio, and zeta potential to identify a definitive factor that governs the effect in the rheology of cement pastes. However, no definitive evidence was found that any of these characteristics dominated the measured effects.<br>The CNC dosage at which the maximum yield stress reduction occurred increased with the amount of water used in the paste preparation, which provides evidence of the dominance of the water to cement ratio in the rheological impact of CNC.<br>14<br>Isothermal calorimetry showed that CNC cause concerning retardation effects in cement hydration. CNC slurries were then tested for sugars and other carbohydrates that could cause the aforementioned effect, then slurries were filtered, and impurities were detected in the filtrate, these impurities were quantified and characterized, however, the retardation appeared to be unaffected by the amount of the species detected, suggesting that the crystal chemistry, which is a consequence of the production method, is responsible of this retardation.<br>This work explores the benefits and drawbacks of the use of CNC in cement composites by individually approaching rheology and heat of hydration on a range of physical and chemical tests to build a better understanding of the observed effects.<br>Understanding the effect of CNCs on cement paste rheology can provide insights for future work of CNCs applications in cement composites.

<div> <p><a>Polymer nanocomposites are envisioned for use in many advanced applications, such as structural industries, aerospace, automotive technology and electronic materials, due to the improved properties like mechanical strengthening, thermal and chemical stability, easy bulk processing, and/or light-weight instigated by the filler-matrix combination compared to the neat matrix. In recent years, due to increasing environmental concerns, many industries are inclining towards developing sustainable and renewable polymer nanocomposites. Cellulose nanomaterials (CNs), including cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), have gained popularity due to their excellent mechanical properties and eco-friendliness (extracted from trees, algae, plants etc.). However, to develop CN-reinforced nanocomposites with industrial applications it is necessary to understand impact of hygroscopic swelling (which has very limited </a>quantitative study at present), aspect ratio, orientation, and content of CNs on the overall performance of nanocomposites; and overcome the low dispersibility of CNs and improve their compatibility with hydrophobic matrix. In this work, we attempt to understand the influence of single nanocrystals in the hygroscopic and optical response exhibited by nanostructured films; effect of CNCs on the properties of PVA/CNC fibers by experimental evidence with mathematical modeling predictions; and hydrophobized CNFs using a facile, aqueous surface modification to improve interfacial compatibility with epoxy. </p><p><br></p> <p>To evaluate the effect of CNC alignment in the bulk response to hygroscopic expansion, self-organized and shear-oriented CNC films were prepared under two different mechanisms. The coefficient of hygroscopic swelling (CHS) of these films was determined by using a new contact-free method of Contrast Enhanced Microscopy Digital Image Correlation (CEMDIC) that enabled the characterization of dimensional changes induced by hygroscopic swelling of the films. This method can be readily used for other soft materials to accurately measure hygroscopic strain in a non-destructive way. By calculating the CHS values of CNC films, it was determined that hygroscopic swelling is highly dependent on the alignment of nanocrystals within the films, with aligned CNC films showing dramatically reduced hygroscopic expansion than randomly oriented films. Finite element analysis was used to simulate moisture sorption and kinetics profile which further predicted moisture diffusion as the predominant mechanism for swelling of CNC films. </p> <p><br></p><p>To study the effects of different types and aspect ratios of CNCs on mechanical, thermal and morphological properties of polyvinyl alcohol (PVA) composite <a>fibers, CNCs extracted from wood pulp and cotton were reinforced into PVA to produce fibers by dry-jet-wet spinning. The fibers were collected as-spun and with first stage drawing up to draw ratio 2. </a>The elastic modulus and tensile strength of the fibers improved with increasing CNC content (5 – 15 wt. %) at the expense of their strain-to-failure. The mechanical properties of fibers with cotton CNC were higher than the fibers with wood CNC when the same amount of CNCs were added due to their higher aspect ratio. The degree of orientation along the spun fiber axis was quantified by 2D X-ray diffraction. As expected, the CNC orientation correlates to the mechanical properties of the composite fibers. Micromechanical models were used to predict the fiber performance and compare with experimental results. Finally, surface and cross-sectional morphologies of fibers were analyzed by scanning electron microscopy and optical microscopy.</p><p><br></p> <p>To improve the dispersibility and compatibility of CNFs with epoxy, CNFs were modified by using a two-step water-based method where tannic acid (TA) acts as a primer with CNF suspension and reacts with hexadecylamine (HDA), forming the modified product as CNF-TA-HDA. The modified (-m) and unmodified (-um) CNFs were filled into hydrophobic epoxy resin with a co-solvent (acetone), which was subsequently removed to form a solvent-free two component epoxy system, followed by addition of hardener to cure the resin. Better dispersion and stronger adhesion between fillers and epoxy were obtained for m-CNF than the um-CNF, resulting in better mechanical properties of nanocomposites at the same loading. Thermal stability and the degradation temperature of m-CNF/epoxy improved when compared to neat epoxy. </p> </div> <br>

Aerogéis de hidroxipropil metilcelulose (HPMC) com diferentes graus de substituição por grupos metila (DS) e hidroxipropila (MS) foram preparados por liofilização utilizando diferentes ácidos como agentes de reticulação, a saber: ácido cítrico, ácido oxálico e ácido tereftálico. Nanocristais de celulose bacteriana (BCN) neutros e negativamente carregados foram utilizados como carga de reforço nas concentrações de 5% (m/m) e 15% (m/m) em relação à massa da matriz. Os resultados indicaram que HPMCs com menores valores de DS e maiores valores de MS resultam em aerogéis com maior eficiência na reticulação. Além disso, agentes de reticulação insolúveis em água minimizaram a capacidade de reticulação, enquanto agentes de reticulação com uma maior quantidade de grupos funcionais ácidos aumentaram a probabilidade e a eficiência da reação de reticulação das cadeias de HPMC. Os aerogéis apresentaram alta estabilidade em água, solventes orgânicos e meio ácido, além de apresentar resiliência quanto à deformação em meio aquoso. Os aerogéis apresentaram porosidade de ~98%, densidade média variando de 0,021 à 0,026 (± 0,002) g.cm-3, módulo de Young variando de 101 à 150 (± 19) kPa e capacidade média de absorção de água de 18 g de água/g de aerogel. A adição de carga de reforço resultou em um aumento de até 13% na densidade aparente do aerogel e um aumento médio de 20% no módulo de Young dos materiais. A morfologia dos poros dos aerogéis sintetizados é irregular, com ampla faixa de distribuição de tamanho de poros, podendo variar cerca de 5 &#181;m a 500 &#181;m. Nos aerogéis reforçados, as BCNs encontram-se preferencialmente no interior das paredes dos aerogéis, onde o reforço mecânico é mais eficiente. Isotermas de adsorção de 17&#945;-etinilestradiol (EE) foram realizadas, resultando em capacidades de remoção de até 90%, com possibilidade de reciclo. As isotermas indicam que a matriz HPMC J5MS possui maior afinidade para adsorção de EE e que a adição de BCNs aumenta a afinidade das moléculas pelo substrato. As isotermas foram melhor ajustadas com o modelo de Freundlich, indicando que a adição de 5% de BCNs aumenta a capacidade de adsorção do aerogel, enquanto a adição de 15% de BCNs provoca uma diminuição nesta propriedade. / Aerogels of Hydroxypropyl methylcellulose (HPMC), with different degrees of substitution for methyl groups (MS) and hydroxypropyl groups (DS) were prepared by freeze-drying. The HPMCs were combined with three organic acids as crosslinking agents: citric acid, oxalic acid and terephthalic acid. Bacterial cellulose nanocrystals (BCN) neutral and negatively charged were used as reinforcement particles from 5% to 15% m/m in relation to the polymer mass. The results indicated that HPMC with lower DS and higher MS levels result in aerogels with higher crosslink efficiency. Besides that, crosslinking agents that are water insoluble minimized the crosslinking capacity, while crosslinking agents with more functional acid groups presented higher probability and efficiency in the crosslinking reaction. The aerogels presented high stability in water, organic solvents and acid media, and presented mechanical resilience in aqueous media. The resulting aerogels presented porosity of ~98%, average density of 0.021 to 0.026 (± 0.002) g.cm-3, Young modulus of 101 to 150 (± 19) kPa and an average capacity of water absorption of 18 g of water/g of aerogel. The addition of reinforcement particles resulted in an increase in density up to 13% and an average increase in the Young modulus of 20%. The morphology of the aerogels was irregular, with a wide pore size distribution, varying between de 5 &#181;m a 500 &#181;m. In the reinforced aerogels, the BCNs were found preferably inside the aerogels walls, were the mechanical reinforcement is more efficient. Adsorption isotherms of 17 ethinyl estradiol (EE) revealed removal capacity up to 90% and possibility of adsorbent recycling. The isotherms indicated that the HPMC J5MS has higher affinity for EE molecules and that the use of BCNs increases aerogels affinity. The isotherms were well fitted with the Freundlich model, indicating that the addition of 5% BCN increases the adsorption capacity of the aerogels, while the addition of 15 % BCN results in a decrease in this property.

Aerogéis de hidroxipropil metilcelulose (HPMC) com diferentes graus de substituição por grupos metila (DS) e hidroxipropila (MS) foram preparados por liofilização utilizando diferentes ácidos como agentes de reticulação, a saber: ácido cítrico, ácido oxálico e ácido tereftálico. Nanocristais de celulose bacteriana (BCN) neutros e negativamente carregados foram utilizados como carga de reforço nas concentrações de 5% (m/m) e 15% (m/m) em relação à massa da matriz. Os resultados indicaram que HPMCs com menores valores de DS e maiores valores de MS resultam em aerogéis com maior eficiência na reticulação. Além disso, agentes de reticulação insolúveis em água minimizaram a capacidade de reticulação, enquanto agentes de reticulação com uma maior quantidade de grupos funcionais ácidos aumentaram a probabilidade e a eficiência da reação de reticulação das cadeias de HPMC. Os aerogéis apresentaram alta estabilidade em água, solventes orgânicos e meio ácido, além de apresentar resiliência quanto à deformação em meio aquoso. Os aerogéis apresentaram porosidade de ~98%, densidade média variando de 0,021 à 0,026 (± 0,002) g.cm-3, módulo de Young variando de 101 à 150 (± 19) kPa e capacidade média de absorção de água de 18 g de água/g de aerogel. A adição de carga de reforço resultou em um aumento de até 13% na densidade aparente do aerogel e um aumento médio de 20% no módulo de Young dos materiais. A morfologia dos poros dos aerogéis sintetizados é irregular, com ampla faixa de distribuição de tamanho de poros, podendo variar cerca de 5 &#181;m a 500 &#181;m. Nos aerogéis reforçados, as BCNs encontram-se preferencialmente no interior das paredes dos aerogéis, onde o reforço mecânico é mais eficiente. Isotermas de adsorção de 17&#945;-etinilestradiol (EE) foram realizadas, resultando em capacidades de remoção de até 90%, com possibilidade de reciclo. As isotermas indicam que a matriz HPMC J5MS possui maior afinidade para adsorção de EE e que a adição de BCNs aumenta a afinidade das moléculas pelo substrato. As isotermas foram melhor ajustadas com o modelo de Freundlich, indicando que a adição de 5% de BCNs aumenta a capacidade de adsorção do aerogel, enquanto a adição de 15% de BCNs provoca uma diminuição nesta propriedade. / Aerogels of Hydroxypropyl methylcellulose (HPMC), with different degrees of substitution for methyl groups (MS) and hydroxypropyl groups (DS) were prepared by freeze-drying. The HPMCs were combined with three organic acids as crosslinking agents: citric acid, oxalic acid and terephthalic acid. Bacterial cellulose nanocrystals (BCN) neutral and negatively charged were used as reinforcement particles from 5% to 15% m/m in relation to the polymer mass. The results indicated that HPMC with lower DS and higher MS levels result in aerogels with higher crosslink efficiency. Besides that, crosslinking agents that are water insoluble minimized the crosslinking capacity, while crosslinking agents with more functional acid groups presented higher probability and efficiency in the crosslinking reaction. The aerogels presented high stability in water, organic solvents and acid media, and presented mechanical resilience in aqueous media. The resulting aerogels presented porosity of ~98%, average density of 0.021 to 0.026 (± 0.002) g.cm-3, Young modulus of 101 to 150 (± 19) kPa and an average capacity of water absorption of 18 g of water/g of aerogel. The addition of reinforcement particles resulted in an increase in density up to 13% and an average increase in the Young modulus of 20%. The morphology of the aerogels was irregular, with a wide pore size distribution, varying between de 5 &#181;m a 500 &#181;m. In the reinforced aerogels, the BCNs were found preferably inside the aerogels walls, were the mechanical reinforcement is more efficient. Adsorption isotherms of 17 ethinyl estradiol (EE) revealed removal capacity up to 90% and possibility of adsorbent recycling. The isotherms indicated that the HPMC J5MS has higher affinity for EE molecules and that the use of BCNs increases aerogels affinity. The isotherms were well fitted with the Freundlich model, indicating that the addition of 5% BCN increases the adsorption capacity of the aerogels, while the addition of 15 % BCN results in a decrease in this property.

Abstract Flotation is a well-known and widely used technique for the separation of particles smaller than 250 µm, but efficient performance requires the use of various synthetic chemicals which can potentially damage the health of humans and animals and pollute the environment. Consequently, their replacement through a more environment-friendly and sustainable alternative has been demanded. One promising candidate is cellulose, which is an abundant natural polymer that is environment-friendly and can be treated chemically and physically to yield tailored properties and thus a potential for use in processes such as flotation. This work focuses on the use of cellulose-based reagents in flotation processes to replace the often harmful conventional reagents derived from mineral oil, plant oils or animal fats. The physico-chemical properties of cellulose differ from those of conventional reagents, leading to differences in performance during flotation. In particular, the chemical and morphological heterogeneity of cellulose affects its properties and thus its interaction with minerals and water. Consequently, its use requires the study of the fundamentals of flotation and their application including the physico-chemical heterogeneity of cellulose to determine the optimum conditions and enable efficient performance. This work focuses on the determination of the thermodynamic surface energetics of solid particles and changes in this after reagent adsorption, using the inverse gas chromatography technique in a dry atmosphere. Furthermore, interactions between cellulose and minerals immersed in water are investigated using the DLVO theory, the interaction forces between cellulose and the minerals being derived and correlated with flotability. The importance of free surface charges is then considered by investigating the electric surface potential of cellulose-coated minerals in connection with particle-bubble attachment efficiency. At the same time, conventional amphiphilic reagents are used and its performances are related to cellulose-based reagents. / Tiivistelmä Vaahdotus on kaivannaisteollisuudessa laajasti käytössä oleva prosessi, jonka avulla saadaan erotettua tehokkaasti pieniä, alle 250 µm kokoisia partikkeleita. Vaahdotuksen apuaineena käytetään erilaisia synteettisiä kemikaaleja, jotka voivat aiheuttaa harmia ympäristölle. Siksi niiden korvaaminen ympäristöystävällisemmillä vaihtoehdoilla on tärkeää. Yksi lupaava vaihtoehto korvaavaksi materiaaliksi on selluloosa. Selluloosa on uusiutuva ja ympäristöystävällinen luonnonpolymeeri, josta voidaan valmistaa kemiallisesti ja fysikaalisesti käsittelemällä erilaisia biokemikaaleja. Näitä voidaan soveltaa erilaisissa prosesseissa, myös vaahdotuksessa. Tässä työssä keskitytään selluloosapohjaisten kemikaalien käyttöön vaahdotuksessa tavanomaisten, usein haitallisten synteettisten kemikaalien korvaamiseksi. Selluloosan fysikaaliskemialliset ominaisuudet eroavat synteettisten vaahdotuskemikaalien ominaisuuksista, mikä vaikuttaa niiden vuorovaikutukseen mineraalien ja veden kanssa. Erityisesti selluloosan kemiallinen ja morfologinen heterogeenisuus on keskeinen tekijä. Selluloosan hyödyntäminen tulevaisuuden vaahdotuskemikaalina edellyttää selluloosan ja mineraalien vuorovaikutuksen syvällistä ymmärtämistä. Tässä työssä tutkitaan selluloosan ja mineraalien vuorovaikutusta sekä IGC-menetelmän avulla, että DLVO-teorian että pintavarausmittausten avulla. Lisäksi tutkitaan selluloosan ja mineraalien vuorovaikutusvoimien yhteyttä vaahdotusprosessin onnistumiseen ja saavutettuja tuloksia verrataan kaupallisten reagenssien toimintaan.

Les nanocristaux de cellulose (NCC), obtenus par hydrolyse acide des microfibrilles de cellulose native sous forme de suspensions colloïdales aqueuses, sont des nanoparticules biosourcées ayant des propriétés mécaniques et optiques particulièrement séduisantes pour la conception de nanomatériaux à haute performance. Pour éliminer certaines de leurs limitations comme la sensibilité au sel et l'absence de contrôle de leurs interactions, nous nous sommes attachés au cours de ce travail à modifier chimiquement ces NCC par greffage de chaînes de polymère thermosensible de la famille de polyétheramines Jeffamine® sur leur surface. La première méthode de greffage utilisée faisait appel à une oxydation TEMPO suivie d'un couplage peptidique. Après l'optimisation de la réaction de greffage, les nouveaux systèmes (NCC-g-Jeffamine) ont été caractérisés et de nouvelles propriétés ont été identifiées notamment leur insensibilité au sel, leur capacité de redispersion dans des solvants organiques, leur caractère tensioactif, leur stabilité thermique améliorée ainsi que leur thermoagrégation réversible. L'étude structurale par diffusion des neutrons aux petits angles a permis d'avoir des informations sur les épaisseurs des couches de polymère greffé ainsi que sur la conformation des chaînes. De nouvelles caractéristiques de l'auto-organisation en phase chirale-nématique de ces nouveaux systèmes ont été notées concernant leur diagramme de phase et leur pas cholestériques. La deuxième méthode de greffage explorée consistait en une oxydation aux ions métapériodate suivie d'une amination réductrice. Les résultats ont montré un détachement partiel des chaînes de cellulose suite à l'oxydation puis leur détachement complet après le greffage du polymère pour obtenir des copolymères cellulose-Jeffamine ayant éventuellement des propriétés intéressantes à étudier. / Cellulose nanocrystals (CNC), obtained by acid hydrolysis of native cellulose microfibrils as colloidal aquous suspensions, are bioresourced nanoparticles that have great mechanical and optical properties well adapted for the conception of new nanomaterials with high performance. In order to eliminate some of their limitations like sensitivity to salt and absence of interactions control, we studied in this work the chemical modification of these CNC by grafting thermoresponsive polymer chains (polyetheramines Jeffamine®) on the their surface. A first grafting strategy used was a TEMPO oxidation followed by peptidic coupling. After the optimization of the grafting reaction, the new systems (CNC-g-Jeffamine) were characterized and new properties were identified particularly their insensitivity to salts, their ability to be redispersed in organic solvents, their surfactant character, their enhanced thermal stability and their reversible thermoagregation. The structural study using small angles neutrons scattering gave us information about thicknesses of the polymer corona and the chains conformation. New characteristics of their self-assembly into chiral-nematic phases were noticed more particularly concerning phase diagrams and cholesteric pitches. The second grafting strategy consisted in an oxidation using periodate ion followed by reductive amination. Results showed a partial detachment of cellulose chains after oxidation. A complete detachment was observed after grafting the polymer chains to finally obtain cellulose-Jeffamine copolymers which could have interesting properties to study.

Ce travail porte sur les propriétés des nanocristaux de cellulose, leur modification de surface et le développement de matériaux avancés. Diverses approches sont utilisées sur ces substrats nanométriques visant à modifier leurs propriétés de surface et étendre leur utilisation dans des applications très sophistiquées, telles que la postsulfation et la désulfatation, le greffage et l'adsorption de polymères, l’oxydation sélective, le greffage moléculaire et l'inclusion "hôte-invité". Sur la base de modifications de surface, l'analyse des propriétés (pour différents taux de groupements sulfates) et divers nanomatériaux dérivés des nanocristaux de cellulose sont étudiés et préparés, notamment des nanocristaux sulfatés à différents taux, des nanocomposites extrudés, des éponges biocomposites et des hydrogels supramoléculaires. L'effet d’un gradient de groupements sulfates sur la chimie de surface, la morphologie et les propriétés physiques des nanocristaux de cellulose est discuté et notamment quatre modèles de section transversale sont comparés pour la détermination de la mesure du degré de substitution surfacique des nanocristaux de cellulose. Une stratégie nouvelle de protection impliquant une double couche polymère et la compatibilisation physique et/ou chimique des nanocristaux de cellulose est proposée afin de promouvoir à la fois la stabilité thermique des nanoparticules et la compatibilité des nanocristaux avec des matrices polymères non polaires au cours de la mise en forme par extrusion. En participant àla réticulation pour la construction de matériaux avancés, des nanocristaux de cellulose sélectivement oxydés (et de la cellulose microfibrillée oxydée pour comparaison) sont introduits dans de l'alginate pour développer des éponges biocomposites présentant une meilleure stabilité mécanique et une meilleure stabilité structurelle. Grâce à la conception intelligente par inclusion 'hôte-invité' in situ entre des nanocristaux de cellulose chimiquement modifiés et la cyclodextrine,deux polysaccharides hydrophiles sont combinés dans des hydrogels supramoléculaires pour l'administration de médicaments. En un mot, cette thèse contribue à l’avancée des nanocristaux de cellulose dans les domaines de l'analyse des propriétés et le développement des applications. / The present work focuses on the properties of cellulose nanocrystals, their surface modification and development of advanced materials. Diverse approaches are employed on these nanoscaled substrates aiming to modify their surface properties and extend their use in highly sophisticated applications, such as postsulfation and desulfation, polymer grafting and adsorption, selective oxidation, molecular grafting, and ‘host-guest' inclusion. On the basis of surface modifications, properties analysis (for different sulfate group contents) and various nanomaterials derived from cellulose nanocrystals are investigated and prepared, including gradient sulfated nanocrystals, extruded nanocomposites, biocomposite sponges, and supramolecular hydrogels. The effect of gradient degrees of sulfate groups on cellulose nanocrystals to surface chemistry, morphology and physical properties are discussed, particularly four cross-section models are compared for the determination of the surface degree of substitution on cellulose nanocrystals. A novel strategy involving a double-polymer-layer shield and physical and/or chemical compatibilization of cellulose nanocrystals is proposed, in order to realize both improvement of thermal stability and promotion of compatibility for nanocrystals with non-polar polymeric matrices during processing by melt-extrusion. With the idea of participating as crosslinking aid for the construction of advanced materials, selectively oxidized cellulose nanocrystals (with oxidized microfibrillated cellulose as comparison) are introduced in alginate for the development of biocomposite sponges with improved mechanical stability or structural stability. Through the smart design of in situ ‘host−guest' inclusion between chemically modified cellulose nanocrystals and cyclodextrin, two hydrophilic polysaccharides are combined in supramolecular hydrogels for use as drug delivery. In a word, this dissertation contributes to the advances of cellulose nanocrystals in the topics of property analysis and application development.

Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2017-06-02T14:05:02Z No. of bitstreams: 1 TeseDDSP.pdf: 5654501 bytes, checksum: 314e8dafc9e9b26a7437132de9501321 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-06-05T17:01:18Z (GMT) No. of bitstreams: 1 TeseDDSP.pdf: 5654501 bytes, checksum: 314e8dafc9e9b26a7437132de9501321 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-06-05T17:01:24Z (GMT) No. of bitstreams: 1 TeseDDSP.pdf: 5654501 bytes, checksum: 314e8dafc9e9b26a7437132de9501321 (MD5) / Made available in DSpace on 2017-06-05T17:07:15Z (GMT). No. of bitstreams: 1 TeseDDSP.pdf: 5654501 bytes, checksum: 314e8dafc9e9b26a7437132de9501321 (MD5) Previous issue date: 2016-07-15 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Solution blow spinning is a technique to produce micro- and nano-scale fibers, forming films with high porosity and surface area. Chemical modifications or the incorporation of nanostructures in these fibers can improve the performance of these films for various applications, such as membranes, tissue engineering and sensors. Therefore, the aim of this work was to study poly(lactic acid) (PLA) films obtained by solution blow spinning reinforced with cellulose nanocrystals (CNC). First, different solvents were evaluated in order to determine the best processing conditions and the feasibility of using the solvent dimethyl carbonate (DMC) in the production of PLA films by solution blow spinning. Polymer concentration showed to be the most significant parameter affecting fiber diameter and DMC presented advantages over 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) and chloroform due its less toxicity, and therefore, is an alternative solvent with an affordable price, using a more environmentally-friendly process. Subsequently, the CNCs were extracted from bleached eucalyptus kraft pulp by sulfuric acid hydrolysis, which were chemically modified with maleic anhydride (CNCMA). Then, composite films of PLA/CNC and PLA/CNCMA were obtained by solution blow spinning and the results indicated that the addition of nanocrystals did not significantly affected fiber diameters, although the fiber diameters tended to decrease with the increase of the nanocrystals concentration. The results also indicated that the nanocrystals may have increased the degree of PLA polymer chains orientation and that the composite films presented a more hydrophilic behavior when compared to the pure PLA film. It suggests that some of the nanocrystals may be on the surface of the fibers, indicating that these composite films are promising for filter and adsorbents membranes application. / A técnica de fiação por sopro em solução produz fibras em escala micro e nanométrica, formando filmes com elevada porosidade e área superficial. Modificações químicas ou a incorporação de nanoestruturas nestas fibras podem melhorar o desempenho destes filmes para diversas aplicações, como por exemplo, membranas, engenharia de tecidos e sensores. Portanto, o objetivo deste trabalho foi estudar filmes de poli(ácido lático) (PLA) obtidos por fiação por sopro em solução reforçados com nanocristais de celulose (CNC). Primeiramente, avaliou-se diferentes solventes a fim de determinar as melhores condições de processamento e a viabilidade de uso do solvente dimetilcarbonato (DMC) na obtenção de filmes de PLA por fiação por sopro em solução. A concentração de polímero mostrou ser o parâmetro mais significativo que afeta o diâmetro das fibras e que o DMC possui vantagens sobre o 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) e o clorofórmio por ser menos tóxico, sendo, portanto, um solvente alternativo com preço acessível, utilizando um processo ambientalmente mais correto. Em seguida, foram extraídos os CNC a partir da polpa branqueada de eucalipto via hidrólise com ácido sulfúrico, os quais foram modificados quimicamente com anidrido maleico (CNCMA). Então, foram obtidos filmes compósitos de PLA/CNC e PLA/CNCMA por fiação por sopro em solução e os resultados indicaram que a adição dos nanocristais não alterou significativamente o diâmetro das fibras, embora observou-se uma tendência de redução nos diâmetros com o aumento da concentração dos nanocristais. Os resultados também indicaram que os nanocristais podem ter aumentado o grau de orientação das cadeias poliméricas do PLA e que os filmes compósitos apresentaram caráter mais hidrofílico quando comparados ao filme de PLA puro. Isto sugere que parte dos nanocristais possam estar na superfície das fibras, indicando que estes filmes compósitos são promissores para aplicação em membranas filtrantes e adsorventes. / CNPQ: 202445/2014-3