Estudamos as propriedades eletrônicas, estruturais e hiperfinas, nos sítios de nitrogênio, para o composto imidazol nas fases gasosa e sólida. Utilizamos o método PAW que é um método ab initio all-electron, dentro da Teoria do Funcional da Densidade, através do código computacional CP-PAW. Nossos valores, tanto para a fase gasosa quanto para a fase cristalina do gradiente de campo elétrico no núcleo, de freqüência de acoplamento quadrupolar (ν) e parâmetro de assimetria (η) estão em ótima concordância com os resultados experimentais da literatura e são os primeiros resultados obtidos, por método ab initio no espaço recíproco, para os átomos de nitrogênio no imidazol cristalino. Utilizamos resultados da literatura e também aqui calculados para estudar a tendência de comportamento tanto de ν quanto de η para diferentes meros (um, dois, três, cadeia infinita) e cristal investigando, assim, a estreita influência das ligações de hidrogênio sobre os valores do Gradiente de Campo Elétrico nos núcleos de nitrogênio. / Here we study structural, electronic and hyperfine properties at the Nitrogen sites in imidazole in the gas and the crystal phases. We use the PAW method which is an ab initio all electron method in the framework of the Density Functional Theory, as embodied in the computer code CP-PAW. The results for quadrupole coupling (ν) and asymmetry parameter (η) at the gas and at the crystal phases are in excellent agreement with the experimental values in the literature. This is the first time that such calculations are performed for the crystalline imidazole through a reciprocal space approach. We also study the behavior of both ν and η trends studing diferent meres (one, two, three and infinite chain) and cristal to investigate the influence of hydrogen bonding on the Electric Field Gradient at the nucleus.

Estudamos as propriedades eletrônicas, estruturais e hiperfinas, nos sítios de nitrogênio, para o composto imidazol nas fases gasosa e sólida. Utilizamos o método PAW que é um método ab initio all-electron, dentro da Teoria do Funcional da Densidade, através do código computacional CP-PAW. Nossos valores, tanto para a fase gasosa quanto para a fase cristalina do gradiente de campo elétrico no núcleo, de freqüência de acoplamento quadrupolar (ν) e parâmetro de assimetria (η) estão em ótima concordância com os resultados experimentais da literatura e são os primeiros resultados obtidos, por método ab initio no espaço recíproco, para os átomos de nitrogênio no imidazol cristalino. Utilizamos resultados da literatura e também aqui calculados para estudar a tendência de comportamento tanto de ν quanto de η para diferentes meros (um, dois, três, cadeia infinita) e cristal investigando, assim, a estreita influência das ligações de hidrogênio sobre os valores do Gradiente de Campo Elétrico nos núcleos de nitrogênio. / Here we study structural, electronic and hyperfine properties at the Nitrogen sites in imidazole in the gas and the crystal phases. We use the PAW method which is an ab initio all electron method in the framework of the Density Functional Theory, as embodied in the computer code CP-PAW. The results for quadrupole coupling (ν) and asymmetry parameter (η) at the gas and at the crystal phases are in excellent agreement with the experimental values in the literature. This is the first time that such calculations are performed for the crystalline imidazole through a reciprocal space approach. We also study the behavior of both ν and η trends studing diferent meres (one, two, three and infinite chain) and cristal to investigate the influence of hydrogen bonding on the Electric Field Gradient at the nucleus.

Polymeric microchips have received increasing attention in chemical analysis because polymers have attractive properties, such as low cost, ease of fabrication, biocompatibility and high flexibility. However, commercial polymers usually exhibit analyte adsorption on their surfaces, which can interfere with microfluidic transport in, for example, chemical separations such as chromatography or electrophoresis. Usually, surface modification is required to eliminate this problem. To perform stable and durable surface modification, a new polymer, poly(methyl methacrylate-co-glycidyl methacrylate) (PGMAMMA) was prepared for microchip fabrication, which provides epoxy groups on the surface. Whole surface atom transfer radical polymerization (ATRP) and in-channel ATRP approaches were employed to create uniform and dense poly(ethylene glycol) (PEG)-functionalized polymer brush channel surfaces for capillary electrophoresis (CE) separation of biomolecules, such as peptides and proteins. In addition, a novel microchip material was developed for bioanalysis, which does not require surface modification, made from a PEG-functionalized copolymer. The fabrication is easy and fast, and the bonding is strong. Microchips fabricated from this material have been applied for CE separation of small molecules, peptides, proteins and enantiomers. Electric field gradient focusing (EFGF) is an attractive technique, which depends on an electric field gradient and a counter-flow to focus, concentrate and separate charged analytes, such as peptides and proteins. I used the PEG-functionalized copolymer to fabricate EFGF substrates. The separation channel was formed in an ionically conductive and protein resistant PEG-functionalized hydrogel, which was cast in a changing cross-sectional cavity in the plastic substrate. The hydrogel shape was designed to create linear or non-linear gradients. These EFGF devices were successfully used for protein focusing, and their performance was optimized. Use of buffers containing small electrolyte ions promoted rapid ion transport in the hydrogel for achieving the designed gradients. A PEG-functionalized monolith was incorporated in the EFGF separation channel to reduce dispersion and improve focusing performance. Improvement in peak capacity was proposed using a bilinear EFGF device. Protein concentration exceeding 10,000-fold was demonstrated using such devices.

Diffusion is an omnipresent, most fundamental phenomenon in nature and thus critical for the performance of numerous technologies. This is in particular true for nanoporous materials with manifold applications for matter upgrading by separation, purification and conversion. The path lengths of molecular transportation within the industrial plants range from the elementary steps of diffusion within the micropores of the individual particles up to the matter flow over macroscopic distances. Each of them might be decisive in determining overall performance so that detailed knowledge of all modes of mass transfer is crucial for a knowledge-based optimization of the devices with reference to their transport properties. The rate of mass transfer is particularly complicated to be assessed within the individual (adsorbent) particles/crystallites with pore sizes of the order of molecular dimensions. We are going to present two powerful techniques exactly for this application, operating under both equilibrium (Pulsed Field Gradient (PFG) NMR) and non-equilibrium (Microimaging by interference microscopy and IR microscopy) conditions. The potentials of these techniques are demonstrated in a few showcases, notably including the options of transport enhancement in pore hierarchies. The contribution concludes with a survey on present activities within an IUPAC initiative aiming at the elaboration of “guidelines for measurements and reporting of diffusion properties of chemical compounds in nanoporous materials”.

Water and ion transport critically determine the performance of many functional materials and devices, from fuel cells to lithium ion batteries to soft mechanical actuators. This dissertation aims to address some fundamental issues regarding transport and anisotropy, structural heterogeneity and molecular interactions inside ionic polymers. I first discuss a main deficiency of a standard protocol for calibrating high pulsed-field-gradient NMR. I show that high gradient calibration using low γ nuclei is not amenable to measurements on slow diffusing high γ nuclei. Then I employ NMR diffusometry to investigate transport and anisotropy for a series of ionic polymers, from poly(arylene ether sulfone) hydrophilic-hydrophobic multi-block copolymers to polymer blends to perfluorosulfonate random copolymers. For the multi-block copolymers, NMR diffusion measurements yield diffusion anisotropy as a function of water uptake and block lengths. ²H NMR spectroscopy on absorbed D₂O probes membrane alignment modes. These measurements also provide insights into average defect distributions. For the blend membranes, we examine the impact of compatibilizer on their transport properties. An increase in compatibilizer significantly improves the membrane phase homogeneity confirmed by SEM and transport studies. Theories of diffusion in porous media yield changes in domain size and tortuosity that correspond to drastic changes in local restrictions to water diffusion among different blend membranes. NMR relaxometry studies yield multi-component T₁ values, which further probe structural heterogeneities on smaller scales than diffusion experiments. For the random copolymer, the exploration of ion transport reveals inter-ionic associations of ionic liquids (ILs) modulated by hydration level and ionic medium. When ILs diffuse inside ionic polymers, isolated anions diffuse faster (≥ 4X) than cations at high hydration whereas ion associations result in substantially faster cation diffusion (≤ 3X) at low hydration inside membranes, revealing prevalent anionic aggregates. Finally, I present the strategy and analytical protocol for studying ionomer membranes using ILs. The normal cation diffusion contrasts to the anomalous anion diffusion caused by local confinement structures inside the membranes, which vary drastically with temperature and hydration level. These structures correspond to a density variation of SO₃⁻ groups, which define a distribution of local electrical potentials that fluctuate with temperature and nature of ionic media. / Ph. D.

Even though electrophoretic NMR (eNMR) experiments may provide unique chemical information and have been performed for three decades, the technique is still rarely applied, mainly because several experimental sources of artifacts have to be controlled to achieve accurate results. In this thesis, new experimental setups and protocols for accurate and precise eNMR experiments are presented. These include a novel eNMR sample cell, a radiofrequency filter and methods to suppress bulk flow effects. These developments improved the signal-to-noise ratio by roughly an order of magnitude compared to the U-tube setup previously used for eNMR. Convection-compensated pulse sequences in combination with a phase correction method were found to efficiently suppress bulk flow effects in the experiments and greatly increase experimental accuracy. These experimental setups and protocols were applied to probe association of ions and molecules in solution. It is particularly illustrated that the combination of diffusion and eNMR has great potential to provide quantitative results on ionic and molecular association in a variety of systems. The extent to which ionic surfactants associate with uncharged cyclodextrin probed by eNMR yielded very similar results to those obtained by diffusion NMR experiments. Complexation of a large set of small mono- and polyvalent metal cations to poly(ethylene oxide) was quantified by estimating the effective charge of the polymer through combined diffusion and eNMR information. Significant association was found for cations that have a surface charge density below a critical value. Ion pairing between tetramethylammonium cations and a series of anions in several solvents was also probed by diffusion NMR and eNMR experiments. For the monovalent anions in ethanol and ethanol-water mixture a dependence on ionic size was demonstrated. In water, dimethylsulfoxide, and methanol no such trend and very little pairing was observed. In acetonitrile, a different pattern was seen that did not correlate well with any single ionic parameter. An experimental cell and procedures for electrokinetic studies of solvated proton-conducting polymer materials is also presented. Electro-osmotic flow and diffusion were studied for each molecular component in water-methanol mixtures that swell Nafion membranes. / Elektroforetisk NMR (eNMR) är en experimentell metod som funnits i tre decennier och som kan ge unik kemisk information. Ändå används den sällan då flera experimentella artefakter måste korrigeras för, om man ska få korrekta resultat. I denna avhandling presenteras nya experimentella uppställningar och protokoll ämnade att uppnå korrekta och noggranna resultat. Dessa inkluderar en ny mätcell, ett radiofrekvensfilter och metoder för att minimera effekten av samtidiga bulkflöden i provlösningen. Sammantaget uppnås ungefär en storleksordning högre signal-brus-förhållande jämfört med den U-rörsuppställning som tidigare använts. Konvektions-kompenserande pulssekvenser i kombination med en faskorrektionsteknik minskade också bulkflödeseffekter effektivt, vilket ökade resultatens noggrannhet högst avsevärt. De experimentella uppställningarna och protokollen användes här för att mäta association av joner och molekyler i lösning. Mätningarna visar att kombinationen diffusions- och eNMR har en stor potential att kvantitativt kunna bestämma associationgraden i många olika typer av kemiska system. Associationsgraden mellan joniska tensider och cyklodextriner undersöktes både med eNMR och diffusions-NMR, och resultaten var mycket lika. Komplex-bildningen mellan en serie enkel- och flerladdade metalljoner och poly-(etylenoxid) kvantifierades genom att uppskatta polymerens effektiva laddning från kombinerad diffusions- och eNMR. Betydande komplexbildning hittades för katjoner med ytladdningstäthet under ett kritiskt värde. Jonparbildning mellan tetrametylammoniumjoner och en serie av anjoner i flera olika lösningsmedel undersöktes också med diffusions- och eNMR. För de monovalenta anjonerna i etanol och etanol-vatten-blandning påvisades ett samband med jonstorleken. I vatten, dimetylsulfoxid och metanol var däremot jonparbildningen låg och inget liknande samband hittades. I acetonitril observerades ett annat mönster, som inte korrelerade bra med någon av anjonernas normala joniska karakteristika. Slutligen presenteras en mätcell och procedurer för elektrokinetiska studier i de solvatiserade protonledande polymermaterial som bland annat används i bränsleceller. Elektroosmotiskt flöde och diffusion uppmättes för varje molekylär komponent i Nafion-membran solvatiserade av vatten-metanol-blandningar. / QC20100709

The results of a solid-state 11B NMR study of a series of boronic acids, boronic esters, and boronic acid catechol cyclic esters with aromatic substituents are reported in this thesis. Boron-11 electric field gradient (EFG) and chemical shift (CS) tensors obtained from analyses of spectra acquired in magnetic fields of 9.4 T and 21.1 T are demonstrated to be useful for gaining insight into the molecular and electronic structure about the boron nucleus. It can be concluded that when adequate electronic variation is present in the compounds being studied, Ω is generally the most characteristic boron NMR parameter of the molecular and electronic environment for boronic acids and esters. Importantly, these data are only reliably accessible in ultrahigh magnetic fields. The experimental span values result from a delicate interplay of several competing factors, including hydrogen bonding, the value of the dihedral angle, and the type of aromatic ring system present.

The results of a solid-state 11B NMR study of a series of boronic acids, boronic esters, and boronic acid catechol cyclic esters with aromatic substituents are reported in this thesis. Boron-11 electric field gradient (EFG) and chemical shift (CS) tensors obtained from analyses of spectra acquired in magnetic fields of 9.4 T and 21.1 T are demonstrated to be useful for gaining insight into the molecular and electronic structure about the boron nucleus. It can be concluded that when adequate electronic variation is present in the compounds being studied, Ω is generally the most characteristic boron NMR parameter of the molecular and electronic environment for boronic acids and esters. Importantly, these data are only reliably accessible in ultrahigh magnetic fields. The experimental span values result from a delicate interplay of several competing factors, including hydrogen bonding, the value of the dihedral angle, and the type of aromatic ring system present.

The results of a solid-state 11B NMR study of a series of boronic acids, boronic esters, and boronic acid catechol cyclic esters with aromatic substituents are reported in this thesis. Boron-11 electric field gradient (EFG) and chemical shift (CS) tensors obtained from analyses of spectra acquired in magnetic fields of 9.4 T and 21.1 T are demonstrated to be useful for gaining insight into the molecular and electronic structure about the boron nucleus. It can be concluded that when adequate electronic variation is present in the compounds being studied, Ω is generally the most characteristic boron NMR parameter of the molecular and electronic environment for boronic acids and esters. Importantly, these data are only reliably accessible in ultrahigh magnetic fields. The experimental span values result from a delicate interplay of several competing factors, including hydrogen bonding, the value of the dihedral angle, and the type of aromatic ring system present.

Magnetic resonance (MR) is a highly versatile technique with great potential for use in industrial applications; from the in situ study of unit operations to the optimisation of product properties. This thesis, concerned with the latter, is divided into two parts. Firstly, dynamic MR is applied to characterise the flow behaviour, or rheology, of process fluids. Such characterisation is typically performed using conventional rheometry methods operating offline, with an online, or inline, method sought for process control and optimisation. Until recently, MR was an unlikely choice for this application due to the requirement of high-field MR hardware. However, recent developments in low-field MR hardware mean that the potential of MR in such applications can now be realised. Since the implementation of MR flow imaging is challenging on low-field MR hardware, two new approaches to MR rheometry are described using pulsed field gradient (PFG) MR. A cumulant analysis of the PFG MR signal is first used to characterise the rheology of model power-law fluids, namely xanthan gum-in-water solutions, accurate to within 5% of conventional rheometry, the data being acquired in only 6% of the time required when using MR flow imaging. The second approach utilises a Bayesian analysis of the PFG MR signal to characterise the rheology of model Herschel--Bulkley fluids, namely Carbopol 940-in-water solutions; data are acquired in only 12% of the time required for analysis using MR flow imaging. The suitability of the Bayesian MR approach to study process fluids is demonstrated through experimental study on an alumina-in-acetic acid slurry used by Johnson Matthey. Secondly, MR imaging is used to provide insights into the origins and mechanisms of colloidal gel collapse. Many industrial products are colloidal gels, a space-spanning network of attractive particles with a yield stress. Colloidal gels are, however, known to undergo gravitational collapse after a latency period, thus limiting the shelf-life of products. This remains poorly understood, with a more detailed understanding of both fundamental interest and practical importance. To this end, MR imaging is applied offline to investigate the phase behaviour of colloidal gels. In particular, a comparison of the simulated and experimental phase diagrams suggests gravitational gel collapse to be gravity-driven. Furthermore, measurement of the colloid volume fraction using MR imaging indicates the formation of clusters of colloids at the top of the samples. Whether such clusters initiate gravitational gel collapse is yield stress-dependent; the gravitational stress exerted by a cluster must be sufficient to yield the colloidal gel.