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Ultrastructure of the Primary Cell Wall of Softwood Fibres Studied using Dynamic FT-IR SpectroscopyStevanic Srndovic, Jasna January 2008 (has links)
<p>The primary cell wall is a complex multipolymer system whose composite structure has been mostly determined from chemical and biochemical studies. Although the primary cell wall serves a central role, with regard to the connective properties of fibres, knowledge about the interactions among the polymers, when it comes to the mechanical properties, is very limited. The physical properties of the polymers, i.e. their elastic and viscous deformations, as well as the ultrastructure of the polymers, i.e. the interactions among the polymers in the outer fibre wall layers that lead to this behaviour, are still not fully understood.</p><p>The aim of this study was to examine how the different wood polymers, viz. lignin, protein, pectin, xyloglucan and cellulose, interact in the outer fibre wall layers of the spruce wood tracheid. The initial objective was to separate an enriched primary cell wall material from a first stage TMP, by means of screening and centri-cleaning. From this material, consisting of the primary cell wall (P) and outer secondary cell wall (S1) materials, thin sheets were prepared and analysed using a number of different analytical methods. The major measuring technique used was dynamic Fourier transform infra-red (FT-IR) spectroscopy in combination with dynamic 2D FT-IR spectroscopy. This technique is based on the detection of small changes in molecular absorption that occur when a sinusoidally stretched sample undergoes low strain. The molecular groups affected by the stretching respond in a specific way, depending on their environment, while the unaffected molecular groups provide no response to the dynamic spectra, by producing no elastic or viscous signals. Moreover, the dynamic 2D FT-IR spectroscopy provides useful information about various intermolecular and intramolecular interactions, which influence the reorientability of functional groups in a polymer material.</p><p>Measurements of the primary cell wall material, using dynamic FT-IR spectroscopy, indicated that strong interactions exist among lignin, protein and pectin, as well as among cellulose, xyloglucan and pectin in this particular layer. This was in contrast to the secondary cell wall, where interactions of cellulose with glucomannan and of xylan with lignin were dominant. It was also indicated that the most abundant crystalline cellulose in the primary cell wall of spruce wood fibres is the cellulose Iβ allomorph, which was also in contrast to the secondary cell wall, where the cellulose Iα allomorph is more dominant. The presence of strong interactions among the polymers in the primary cell wall and, especially, the relatively high content of pectin and protein, showed that there is a very good possibility of selectively attacking these polymers in the primary cell wall. The first selective reaction chosen was a low degree of sulphonation, applied by an impregnation pretreatment of chips with a very low charge of sodium sulfite (Na2SO3). This selective reaction caused some structural modification of the lignin, a weakening of the interactions between lignin;pectin, lignin;protein and pectin;protein, as well as an increased softening of the sulphonated primary cell wall material, when compared to the unsulphonated primary cell wall material. All this resulted in an increased swelling ability of the material.</p>
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Thermodynamic and Spectroscopic Studies on the Molecular Interaction of Doxorubicin (DOX) with Negatively Charged Polymeric NanoparticlesGaurav, Raval 26 November 2012 (has links)
The aim of this study was to investigate the molecular interactions of the anti-cancer drug Doxorubicin (DOX) with poly(methacrylic acid) grafted starch nanoparticles (PMAA-g-St). In order to fully understand the DOX/PMAA-g-St system, we conducted in-depth studies on DOX dimer dissociation and DOX/PMAA-g-St binding interactions using various techniques such as isothermal titration calorimetry (ITC), dynamic light scattering (DLS), and fluorescence and absorption spectroscopy. Based on our experimental results, we developed a quantitative thermodynamic model with relevant parameters such as dissociation constant, Kd, as well as enthalpy of binding, ΔH, in order to explain DOX/PMAA-g-St interactions. In addition, we also studied the effect of environmental factors such as pH and NaCl on DOX self-association and DOX/PMAA-g-St complex formation. In conclusion, the combination of results obtained from various techniques as well as the multispecies equilibrium model, enables us to interpret quantitatively the data of drug loading onto and release from polymeric nanoparticles.
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Importance of Molecular interactions to Design Non-ionic Coacervates for Drug Delivery ApplicationsKundu, Mangaldeep January 2021 (has links)
No description available.
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Ultrastructure of the Primary Cell Wall of Softwood Fibres Studied using Dynamic FT-IR SpectroscopyStevanic Srndovic, Jasna January 2008 (has links)
The primary cell wall is a complex multipolymer system whose composite structure has been mostly determined from chemical and biochemical studies. Although the primary cell wall serves a central role, with regard to the connective properties of fibres, knowledge about the interactions among the polymers, when it comes to the mechanical properties, is very limited. The physical properties of the polymers, i.e. their elastic and viscous deformations, as well as the ultrastructure of the polymers, i.e. the interactions among the polymers in the outer fibre wall layers that lead to this behaviour, are still not fully understood. The aim of this study was to examine how the different wood polymers, viz. lignin, protein, pectin, xyloglucan and cellulose, interact in the outer fibre wall layers of the spruce wood tracheid. The initial objective was to separate an enriched primary cell wall material from a first stage TMP, by means of screening and centri-cleaning. From this material, consisting of the primary cell wall (P) and outer secondary cell wall (S1) materials, thin sheets were prepared and analysed using a number of different analytical methods. The major measuring technique used was dynamic Fourier transform infra-red (FT-IR) spectroscopy in combination with dynamic 2D FT-IR spectroscopy. This technique is based on the detection of small changes in molecular absorption that occur when a sinusoidally stretched sample undergoes low strain. The molecular groups affected by the stretching respond in a specific way, depending on their environment, while the unaffected molecular groups provide no response to the dynamic spectra, by producing no elastic or viscous signals. Moreover, the dynamic 2D FT-IR spectroscopy provides useful information about various intermolecular and intramolecular interactions, which influence the reorientability of functional groups in a polymer material. Measurements of the primary cell wall material, using dynamic FT-IR spectroscopy, indicated that strong interactions exist among lignin, protein and pectin, as well as among cellulose, xyloglucan and pectin in this particular layer. This was in contrast to the secondary cell wall, where interactions of cellulose with glucomannan and of xylan with lignin were dominant. It was also indicated that the most abundant crystalline cellulose in the primary cell wall of spruce wood fibres is the cellulose Iβ allomorph, which was also in contrast to the secondary cell wall, where the cellulose Iα allomorph is more dominant. The presence of strong interactions among the polymers in the primary cell wall and, especially, the relatively high content of pectin and protein, showed that there is a very good possibility of selectively attacking these polymers in the primary cell wall. The first selective reaction chosen was a low degree of sulphonation, applied by an impregnation pretreatment of chips with a very low charge of sodium sulfite (Na2SO3). This selective reaction caused some structural modification of the lignin, a weakening of the interactions between lignin;pectin, lignin;protein and pectin;protein, as well as an increased softening of the sulphonated primary cell wall material, when compared to the unsulphonated primary cell wall material. All this resulted in an increased swelling ability of the material. / QC 20101123
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Développement de nouveaux électrolytes solides à base de mélanges de polymères pour les batteries lithiumCaradant, Léa 10 1900 (has links)
Les recherches réalisées au cours de ce doctorat portent sur l’étude et l’optimisation de
mélanges de polymères, utilisés en tant qu’électrolytes solides polymères (SPEs) dans les
batteries lithium et lithium-ion. Les composants de la batterie doivent pouvoir être mis en forme
par un procédé sans solvant (extrusion), afin de réduire les impacts du solvant sur les propriétés
de la batterie et d’optimiser la production (diminution de la toxicité et du temps de production).
Pour répondre à ces objectifs, une étude a d’abord été menée sur des mélanges de
polymères, sélectionnés d’après leurs propriétés individuelles, en se concentrant notamment sur
les interactions entre le sel de lithium et chaque polymère. Un classement des interactions a été
développé et a permis de montrer que le principal facteur les favorisant est le nombre donneur
des groupements fonctionnels polaires présents sur les chaînes polymères. Enfin, les effets de ces
interactions sur les phénomènes de transport ionique dans les mélanges ont été investigués. Par
la suite, l’étude s’est focalisée sur les couples de polymères ayant des propriétés prometteuses
et complémentaires, tels que le poly(oxyde d’éthylène) (POE) ou le polycaprolactone (PCL), qui
ont des conductivités ioniques élevées, et un copolymère butadiène-acrylonitrile hydrogéné
(HNBR), qui possède des propriétés mécaniques intéressantes mais une conductivité ionique
limitée. Il a été conclu que ces mélanges présentent des propriétés encourageantes, comparées
aux SPEs composés d’un unique polymère, telles que des conductivités ioniques élevées sur une
large plage de températures, ainsi que de meilleures propriétés de stabilités mécanique et
thermique. La dernière partie de ces travaux s’est portée sur l’optimisation des propriétés de ces
mélanges, par une méthode innovante de réticulation sélective d’une des phases.
Pour conclure ce doctorat, l’objectif final a été de réaliser un prototype performant de
batterie lithium tout solide, entièrement obtenu par extrusion, et dont l’électrolyte et le liant au
sein des électrodes composites sont composés des électrolytes polymères optimisés. Les résultats
prometteurs obtenus ont permis la soumission d’un brevet, en association avec le partenaire
industriel (TotalEnergies). / The research carried out during this PhD is focused on the study and optimization of
polymer blends, used as solid polymer electrolytes (SPEs) in lithium and lithium-ion batteries. All
components of the battery must be shaped by a solvent-free process (extrusion), in order to limit
impacts of the solvent on the battery properties and improve the production process (reduce
toxicity and production time).
To achieve these objectives, a study was first conducted on a set of polymer blends,
selected on the basis of their individual properties, with particular emphasis on the interactions
between the lithium salt and each polymer. A ranking of the lithium salt solvating ability of these
polymers was developed and revealed that the main factor affecting these interactions is the
donor number of polar functional groups on the polymer backbones. The effects of these
interactions on the ionic transport phenomena in blend electrolytes have been examined.
Subsequent work focused on polymer couples with the most promising and complementary
properties, such as poly(ethylene oxide) (PEO) or polycaprolactone (PCL), which exhibit high ionic
conductivities, and a hydrogenated nitrile butadiene rubber (HNBR) with interesting mechanical
properties but a lower ionic conductivity. It was concluded that these blends show encouraging
properties, compared to single-polymer SPEs, such as higher ionic conductivities over a wide
temperature range, as well as improved mechanical and thermal stability properties. The final
research project was the optimization of these blend electrolytes using an innovative method of
selective cross-linking of one of the polymer phases.
The main aim of this thesis was to develop an efficient prototype of an all-solid-state
lithium battery, entirely obtained by extrusion, in which both the electrolyte and the binder of
the composite electrodes are composed of optimized polymer electrolytes. The promising results
obtained have led to the filing of a patent, in association with the industrial partner
(TotalEnergies).
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Vesicle-Protein Diffusion and Interaction Study Using Time Resolved Fluorescence Correlation SpectroscopyRouhvand, Bahar January 2017 (has links)
No description available.
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A Combined Microscopy and Spectroscopy Approach to Study Membrane BiophysicsKohram, Maryam 15 September 2015 (has links)
No description available.
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