In this study, a novel polyimide (PI) film, consisting of multiwall carbon nanotubes (MWCNTs) dispersed in an Ionic Liquid (IL), were demonstrated to be high shielding effectiveness (SE). The film was potentially useful for screening electromagnetic interference(EMI) in an optical transceiver module. The experimental results showed MWCNT-PI composite dispersed well in IL exhibits a high far-field SE of 38 ~ 45 dB within the frequency range of 1 ~ 3 GHz. It was also demonstrated the MWCNT-PI composite prepared with IL dispersed process have higher SE and lower weight percentage of MWCNTs than those with non-IL-dispersed process. Their intermolecular forces were carefully examined in order to understand dispersion mechanisms among MWCNTs. The aggregation phenomenon of MWCNTs was known, resulting from van der Waals forces. In our study, IL was employed to disperse MWCNTs. A proposal reason was that the attractive force between cation of the IL and £k electrons of MWCNTs is greater than the van der Waals forces among MWCNTs. From conductivity measurement, percolation threshold of the IL-dispersed MWCNT-PI composite was 5.2 wt%; percolation threshold of the non-IL-dispersed MWCNT-PI composite was 11.5 wt%. Given the lower percolation threshold ,we demonstrated the successful dispersion of MWCNT by adding IL. From the results of Raman spectrometer analyses, the IL dispersion was proved to be a physical interaction. Furthermore, the IL-dispersed MWCNT-PI composite was used as package material in monopole antenna and got a near-field SE of 37dB within the frequency of 2.8 GHz. It implied that the IL-dispersed MWCNT-PI composite has an excellent EMI performance.The IL-dispersed MWCNT-PI composite is suitable for packaging low-cost and high-performance optical transceiver modules in the application of the fiber-to-the-home (FTTH) lightwave transmission systems.

There is growing need for technologies to displace traditional petroleum resources. Towards this goal, lignocellulosic biomass is seen as a potential renewable resource for the production of fuels and commodity chemicals. One of the most difficult components of lignocellulose to process is lignin, which is a complex, amorphous aromatic polymer that acts as one of the structural components in plants. Ionic liquids are a class of compounds that are composed completely of anions and cations that, in some cases, can completely dissolve lignocellulosic biomass. The research performed for this dissertation aims to advance the technologies of lignocellulose processing through effective depolymerization of lignin in ionic liquids. Lignin fragments from this depolymerization could be used as a feedstock for further processing into aromatic commodity chemicals or polymers. Additionally, by removing lignin, biomass becomes much more accessible to enzymatic or chemical saccharification as a step towards fermentation into ethanol or other fuels. Both base and acid catalyzed methods were explored, although the base promoted depolymerization of lignin in ionic liquids did not show much promise, as the reaction was never shown to be catalytic. Acidic routes towards lignin depolymerization were more successful. Using the acidic ionic liquid 1-H-3-methylimiazolium chloride, the ether linkages in lignin model compounds could be hydrolyzed with high yields. This technology was also applicable to the whole lignin macromolecule. The mechanisms of this reaction, as well as the effects on lignin were explored with various neutral and acidic ionic liquids, using HPLC, GPC, NMR, FT-IR, and mass spectrometry for analysis of samples. To demonstrate the applications of this technique, pine wood was treated with the acidic ionic liquids to open the structure of the wood to enzymatic saccharification through the removal of lignin and hemicellulose. / text

Newly developed all-cellulose composites (ACCs) can overcome the chemical incoherence between cellulose and other polymers by dissolution and regeneration of a portion of cellulose to create a chemically identical matrix phase. New “close to industry”-processing ways for ACCs were developed to create “thick” ACCs (>1 mm thickness) based on composite processes already used in the composite industry. The ionic liquid (IL) 1-Butyl-3-Methylimidazolium Acetate (BmimAc) is a strong solvent for both, native cellulose and cellulose II. The dissolution process is strongly depended on the temperature and viscosity of the IL-cellulose solution. Next to complete dissolution, rayon fibre can be dissolved partially to achieve the formation of a matrix phase in situ. The highly hydrophilic cellulose based materials show different amounts of shrinkage after composite processing when the coagulant necessary to regenerate the dissolved cellulose is removed by evaporative drying. Multilayered, “thick” composite laminates could be produced by a simple hand-impregnation of rayon and linen textiles with the solvent and partial dissolution of the cellulosic textiles. A solvent infusion process (SIP) based on vacuum assisted resin infusion was successfully developed to process ACCs. The application of pressure during SIP is crucial to achieve good interlaminar adhesion. The SIP based laminates showed improved tensile strength and stiffness compared to the hand impregnation process. An analysis of the processing parameters showed that the drying process used to remove the coagulant is important to achieve good fibre-matrix-bonding as harsh evaporative drying causes shrinkage induced cracks in the created matrix phase. Using ethanol as a coagulant instead of water reduced composite swelling and corresponding shrinkage, but leads to a strong reduction in crystallinity of the regenerated cellulose, as shown X-ray diffraction and solid state NMR measurements. Regeneration in distilled water, followed by drying at room temperature produced the best ACC laminate. The SIP based laminates showed high flexural and impact strength compared to other biocomposites. The composites were also found to be easily compostable especially compared to a PLA-rayon composite. The rayon fibre was processed on an ITA 3D rotary braiding machine, generally used for the processing of stronger and stiffer glass and carbon fibres. A rectangular profile was produced and analysed. The fibre strength and Young’s modulus were unaffected by the braiding process. The braid could be processed into an ACC by immersion in IL for 60 min at 100 °C. The so produced ACCs showed further improvements in tensile and impact strength due to improved through the thickness strength.

Ionic liquids (IL) are salts which are liquid at low temperatures, typically with melting points under 100 °C. In recent years ILs have been treated as novel solvents and used in a wide variety of applications such as analytical and separation processes, electrochemical devices and chemical syntheses. The properties of many ILs have been extensively studied; these studies have primarily focused on the investigation of key physical properties including viscosity, density and solubility. This thesis presents mass spectrometry (MS) and computational data to investigate the intrinsic interactions between a small number of IL ions and also their interactions with contaminants. MS was used to study gas-phase aggregates of three ILs based on the 1-butyl-3- methylimidazolium (C4mim+) cation. The influence of different ion sources was investigated on C4mimCl. Conventional electrospray ionisation (ESI) and nano-ESI techniques were compared with recently developed sonic-spray ionisation (SSI) and plasma assisted desorption ionisation (PADI). SSI was found to be beneficial to the formation of larger aggregates while PADI was significantly less efficient. Gas-phase structures of the singly charged cationic aggregates of C4mimCl were characterised with the aid of collision induced dissociation (CID) and density functional theory (DFT) calculations. Additionally, CID and DFT gave consistent results for the relative stability of the C4mimCl aggregates, showing a good agreement between experiment and theory. Mixed solutions of C4mimCl with a range of metal chloride salts were used to form aggregates incorporating both IL and metal chlorides. LiCl, NaCl, KCl, CsCl, MgCl2 and ZnCl2 were all combined with C4mimCl. Magic number characteristics were observed for a number of pure IL and mixed aggregates. Many of the mixed species were characterised using MS and DFT calculations. In particular, the relative stabilities were determined and the structures of the aggregates were calculated. It was found that the metal ions would normally act as a core for the aggregates with the stability determined by the metal-chlorine binding strength and the steric hindrance of the aggregates. It was necessary to exploit pseudopotentials as opposed to all-electron basis sets for the larger aggregates and aggregates containing heavy atoms. While water is a very effective contaminant for ILs it was not possible to observe gas-phase IL aggregates incorporating this despite using multiple methods. Additionally the presence of protonated aggregates was likewise not observed throughout the range of experiments. Possible structures where these features would be incorporated were studied with DFT to obtain some insight into their lack of formation.

No description available.

Les interactions non-Covalentes entre des protéines et des polysaccharides anioniques tels que les glycosaminoglycanes (GAGs) interviennent dans de nombreux processus physio-Pathologiques tels que la signalisation, la reconnaissance cellulaire, les infections bactériennes et virales ou lors de la progression des cancers. Une des difficultés pour comprendre les mécanismes moléculaires mis en jeu lors de ces interactions réside dans le déchiffrage des informations structurales contenues dans les GAGs. Cette tâche est délicate, surtout en raison du degré variable d'acétylations et de sulfatations de ces GAG's, constituant des limitations importantes pour l'avancée des recherches en glycobiologie. Pour contourner ces restrictions, des méthodes analytiques fines et innovantes, telles que la spectrométrie de masse (MS) offrent de nombreux avantages. Durant cette thèse, trois approches originales basées sur la MS ont été developpées. La première a consisté à synthétiser de nouvelles matrices ioniques liquides limitant la désulfatation et favorisant l'obtention de dépôt homogène pour l'analyse par UV-MALDI-TOF. La seconde a montré le potentiel d'une méthode d'ionisation douce récemment introduite, la désorption ionisation assistée par électronébulisation (DESI) permettant l'analyse directe et en conditions ambiantes d'oligosaccharides anioniques seuls ou sous forme de complexes avec une protéine. Enfin, la troisième a nécessité la fabrication de puces à protéines ou à saccharides pour lanalyse de complexes protéines/GAG en utilisant le couplage de la résonance plasmonique de surface avec la MS (SPR-MS). Ce couplage permet d'effectuer le suivi en temps réel de la formation de complexes entre des protéines et des GAGs, d'en déterminer les constantes de la dissociation, puis de détecter directement par UV-MALDI-TOF les ligands, qu'ils soient de nature protéique ou saccharidique. / The non-Covalent interactions between proteins and anionic polysaccharides such as glycosaminoglycans (GAGs) are involved in several physio-Pathological processes such as cell signalling and recognition, bacterial and viral infections or during cancer progression. One of the obstacles to get the molecular mechanisms involved during these interactions hold in the structural information deciphering within GAG's sequences. This task is delicate especially because of variable level of acetylations and sulfations, constituting important bottleneck in the research advances of the glycobiology field. To bypass these restrictions, accurate and innovative analytical methods such as mass spectrometry (MS) provide numerous advantages. During this Ph.D training, three original MS based approaches have been developed. The first dealt with the synthesis of new ionic liquid matrices, which both restrict desulfation process and favour the homogeneous deposits for UV-MALDI-TOF analysis. The second way used a soft recently introduced ionization method, desorption electrospray ionization (DESI) allowing direct analysis in ambient conditions of anionic oligosaccharides or under complexes with protein. Finally, the third involved the making of protein or saccharide chips for the analysis of protein / GAG complexes using the hyphenation of surpface plasmon resonance with MS (SPR-MS). Thos coupling allows real time monitoring protein / GAG complexes formation, their dissociation constant determination and the direct detection of protéic as wall as saccharidic ligands by UV-MALDI-TOF.

DNA has been widely studied in a variety of solvents. The majority of these solvents consist of either aqueous or organic components. The presence of ions or salts in these solvents can further alter DNA properties by changing the melting point or helical structure. The size, charge, and concentration of these additional components can all affect the behaviour of DNA. A new class of solvents, known as ionic liquids have recently gained popularity. Ionic liquids are comprised of entirely of ions and can be liquid at room temperature. Due to their low volatility and ability to dissolve both polar and non-polar substances, they are generating high levels of interest as ‘green solvents’. Although the interaction between DNA and ionic liquids has been characterized, the potential of this interaction is still being studied. It was discovered that when DNA mixed with DNA intercalating dyes was added to ionic liquids, there was a large reduction in fluorescence. Although this fluorescence drop was believed to occur to removal of the dye molecule from the helix, the strength of this interaction has not been researched. In this thesis, the interaction between different intercalating dyes and different ionic liquids was evaluated. We reasoned that perhaps the difference in interaction could be used as a method of separating the DNA-dye complex, which has previously never been accomplished. For example, it has been established that both DNA and cationic dyes have an affinity for ionic liquids. The relative strength of this affinity is undetermined, as well as the comparison to normal aqueous mediums. Although ionic liquids can drastically alter the stability of the DNA duplex by either raising or decreasing the melting point depending on the ionic liquid chosen, we found that the DNA actually has a higher affinity for the aqueous phase. Conversely, intercalating dyes prefer to partition into the ionic phase. The relative affinities of the two components are strong enough for their respective phases that the complex can be split apart and each component can be extracted, allowing for separation of the two.

Recently, there has been increased effort in researching methods for producing hollow nanostructures because of their potential impact in the fields of catalysis, separation processes, drug delivery, and energy storage and conversion devices. The purpose of this thesis is to describe a method for forming hollow inorganic-organic hybrid nanoboxes and nanoframes. This approach relies upon ionic liquid (1-butyl-3-methyl-imidazolium chloride) mediated auto-templating assembly of CaCO3 and chitosan to form nanoframes (two open faces) and nanoboxes (one open face). The average dimension of the nanostructures formed was 339 ± 95 x 299 ± 89 nm. Detailed structure of nanoboxes and nanoframes were obtained by 3-D electron tomography and X-ray diffraction. Chemical bonding was determined by FTIR, and the ratio of organics to inorganics in the nanostructures was determined by thermal gravimetric analysis. The chitosan to CaCO3 weigh ratio, mixing strength, temperature, and dialysis time were varied to further elucidate the method of formation. It was found that increasing the mixing power caused the equilibrium nanostructure dimension to decrease. On the other hand, varying the experimental temperature in the range of 80 to 160˚C did not affect the nanostructure dimension. The dialysis study showed that during dialysis the nanostructure core was increasingly removed. Nanoframes were observed after 72 hours of dialysis. With further dialysis, there was continued erosion of nanoframes. Results indicate that the concentration gradient and the solubility difference between the mixture components were responsible for this transformation.

none

The existence of Room Temperature Ionic Liquids (RTILs) has been known for a long time, but only recently have they been pulled to the forefront of chemical research. This increase in attention can be attributed to a keen interest in their intrinsic properties for a wide variety of potential applications. RTILs have been used as alternative solvents for organic synthesis as well as catalysis, as well as supports for the purification or extraction of metals. Being ionic in nature and liquid at temperatures below 100°C, RTILs lend themselves to the electrochemist. As a result, they have been looked at for use in electrochemical systems such as high capacity batteries and supercapacitors. Due to their extremely high density of charge carriers relative to more well-known aqueous electrochemical systems, a new theoretical approach must be taken. Currently, a large gap exists between theoretical approaches and experimental results. The work contained within this thesis aims to provide insight into the interface between a RTIL and an electrified gold electrode.