No / The increasing prevalence of poorly soluble drugs in development provides notable risk of new products demonstrating low and erratic bioavailabilty with consequences for safety and efficacy, particularly for drugs delivered by the oral route of administration. Although numerous strategies exist for enhancing the bioavailability of drugs with low aqueous solubility, the success of these approaches is not yet able to be guaranteed and is greatly dependent on the physical and chemical nature of the molecules being developed. Crystal engineering offers a number of routes to improved solubility and dissolution rate, which can be adopted through an in-depth knowledge of crystallisation processes and the molecular properties of active pharmaceutical ingredients. This article covers the concept and theory of crystal engineering and discusses the potential benefits, disadvantages and methods of preparation of co-crystals, metastable polymorphs, high-energy amorphous forms and ultrafine particles. Also considered within this review is the influence of crystallisation conditions on crystal habit and particle morphology with potential implications for dissolution and oral absorption.

No / The Sikhote-Alin (SA) meteorite is an example of a type IIAB octahedrite iron meteorite with ca. 0.5 wt% phosphorus (P) content principally in the form of the siderophilic mineral schreibersite (Fe,Ni)(3)P. Meteoritic in-fall to the early Earth would have added significantly to the inventory of such siderophilic P. Subsequent anaerobic corrosion in the presence of a suitable electrolyte would produce P in a form different to that normally found within endogenous geochemistry which could then be released into the environment. One environment of specific interest includes the low pH conditions found in fumaroles or volcanically heated geothermal waters in which anodic oxidation of Fe metal to ferrous (Fe2+) and ferric (Fe3+) would be coupled with cathodic reduction of a suitable electron acceptor. In the absence of aerobic dioxygen (E-o = +1.229 V), the proton would provide an effective final electron acceptor, being converted to dihydrogen gas (E-o = 0 V). Here we explore the hydrothermal modification of sectioned samples of the Sikhote-Alin meteorite in which siderophilic P-phases are exposed. We report on both, (i) simulated volcanic conditions using low pH distilled water and (ii) geothermally heated sub-glacial fluids from the northern Kverkfjoll volcanic region of the Icelandic Vatnajokull glacier. A combination of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements using the scanning Kelvin probe (SKP) method reveals that schreibersite inclusions are significantly less susceptible to anodic oxidation than their surrounding Fe-Ni matrix, being some 550 mV nobler than matrix material. This results in preferential corrosion of the matrix at the matrix-inclusion boundary as confirmed using topological mapping via infinite focus microscopy and chemical mapping through Raman spectroscopy. The significance of these observations from a chemical perspective is that electrochemically noble inclusions such as schreibersite are likely to have been released into the geological environment through an undermining corrosion of the surrounding matrix, thus affording localised sources of available water-soluble, chemically reactive P in the form of H-phosphite [H2PO3-, Pi(III) as determined by P-31 NMR spectroscopy]. This compound has been shown to have considerable prebiotic chemical potential as a source of condensed P-oxyacids. Here we demonstrate that Pi(III) resulting from the hydrothermal modification of Sikhote- Alin by sub-glacial geothermal fluids can be readily dehydrated into the condensed P-oxyacid pyrophosphite [H2P2O52-, PPi(III)] by dry-heating under mild (85 degrees C) conditions. The potential significance of this latter condensed P-compound for prebiotic chemistry is discussed in the light of its modified chemical properties compared to pyrophosphate [H2P2O72-, PPi(V)].

Yes / Ibuprofen (IBF) is an outstanding non-steroidal drug for analgesic and anti-inflammatory therapies but it exhibits poor solubility in water [1, 2]. Increased dosage administration has been linked to gastrointestinal and cardiovascular complications [3]. Many techniques have been employed to improve the solubility of NSAIDs [4]. In this study, the anti-solvent precipitation method was used to make Ibuprofen nanoparticles (IBF NPs). Optimised preparation parameters such as solvent (ethanol), raw drug concentration (400 mg), solvent/anti-solvent ratio (1:50) and surfactant concentration (0.25 mg/ml) have been studied to yield nanoparticles with a mean size of 58.8 nm, which is confirmed by dynamic light scattering and transmission electron microscopy. These IBF NPs posess increased aqueous solubility compared to the micro counterpart and maintain with chemical integrity indicated by high performance liquid chromatography and Fourier transform infrared spectroscopy. In addition, in vitro cytotoxicity of IBF NPs has been studied on A549 and HaCat cell lines using MTT and LDH assays. Both cells were obtained from ATCC. The A549 cells were grown in a modification of Ham’s F-12, containing L-glutamine, called F-12K. The HaCaT cells were grown in DMEM containing sodium pyruvate (110 mg/l). Normal cell culture and sub-culture were applied and the cells were used after around 45 passages [5]. The cell culture media containing 105cells/ml were placed in a 96-well plate with addition of IBF NPs and Micro form at concentrations in the range of between 6 and 500 ug/ml by diluting them with DMEM and F-12K for use with the HaCaT and A549 cells respectively. After 24, 48 and 72h exposure, the MTT and LDH cytotoxicity assay were performed in triplicates and on three separate experiment cultures and the absorbance was recorded at 570 nm and 492nm respectively with Elisa micro plate reader. The cell viability (%) related to control (cells in culture medium without NPs) was calculated. A very good cytotoxicity profile was observed, indicating an in vitro cytocompatibility of the IBF NPs in these cell culture systems and no significant changes in cytotoxicity compared with Micro IBF. We conclude that our IBF NPs have increased solubility, same chemical integrity and unchanged cytotoxicity compared to IBF Micro drug. Further work will concentrate on optimising more rigorous parameter to produce excellent quality NPs. More detailed characterisation of IBF NPs is to be tested, such as using PXRD and SEM to further corroborate particle shape and size. The range of no toxic in vitro concentrations is also to be further confirmed. Eventually scaled up preparation of IBF NPs will be developed without relinquishing NPs quality. This would improve the potential for in vitro/ in vivo applications and clinical use of IBF NPs and NSAIDs in general.

The thesis presents detailed results of theoretical analyses based on extensive computer simulation studies with an aim to explore, quantify whenever possible, and understand structure and dynamics of polymers and proteins in several complex solvents. In order to make the Thesis coherent, we also study certain aspects of binary mixtures. Based on the phenomena studied, the thesis has been divided into four major parts: I. Dynamics of biological water: Distance dependent variation of dielectric constants in aqueous protein solutions II. Temperature dependent study of structural transformations in aqueous binary mixtures III. Conformation and dynamics of polymers in solution: Role of aqueous binary mixtures IV. Conformational change and unfolding dynamics of proteins: Role of sol-vent environment The above mentioned four parts have further been divided into thirteen chapters. In the following we provide a brief chapter-wise outline of the thesis. Part I consists of two chapters, where we focus on the study of dynamics of biological water and distance dependent variation of static and dynamic proper-ties (including dielectric constant) of water near different proteins. To start with, chapter 1 provides an introduction to the structure and dynamics of biological water. Here we discuss different experimental studies; including dielectric relaxation, NMR and salvation dynamics those explore the bimolecular hydration dynamics in great detail. We also discuss the wide range of computer simulation and theoretical studies that have been carried out to understand the dynamical behaviour of biological water. In chapter 2, we present our molecular dynamics simulation study to ex-plore the distance dependent static and dynamic behaviour of biological water near four different protein surfaces. Proteins are known to have large permanent dipole moments that can influence structure and dynamics of even distant water molecules. Therefore, distance dependence of polarization punctuation can provide important insight into the nature of biological water. We explore these aspects by studying aqueous solutions of four different proteins of different char-acteristics and varying sizes. We find that the calculated dielectric constants of the systems show a noticeable increment in all the cases compared to that of neat water. Total dipole moment auto time correlation function of water is found to be sensitive to the nature of the protein. We also define and calculate the effective dielectric constant of successive layers and find that the layer adjacent to protein always has significantly lower value (∼ 50). However, progressive layers exhibit successive increment of dielectric constant, finally reaching a value close to that of bulk 4–5 layers away. Theoretical analysis providing simple method for calculation of shellwise local dielectric constant and implication of these findings are elaborately discussed in this chapter. Part II deals with the temperature dependent study of aqueous DMSO and ethanol solutions and consists of three chapters. Chapter 3 provides a general introduction to the non-ideality (deviation from Raoult’s law) encountered in different binary mixtures. We discuss different theoretical models for treatment of binary mixtures. Finally we provide a systematic study about the non-ideality observed in aqueous binary mixtures. Here we discuss the anomalies observed in such systems and carry out a brief survey on the existing ideas of structural transformations associated with the solvation of a foreign molecule in water. In chapter 4, we discuss the results of temperature dependent study of struc-tural and dynamic properties of aqueous dimethyl sulfoxide (DMSO) mixture. It is now well-known that aqueous DMSO mixture exhibits signature of perco-lation driven structural aggregation at a mole fraction range xDMSO ≈ 0.15. We study the structural and dynamical change in this binary mixture below and above the percolation threshold along with decreasing temperature. Significant change in the molecular structure of DMSO as well as that of water is observed above the percolation threshold at a lower temperature, particularly at 200K. The structural arrangement of the DMSO molecules is found to be progressively more ordered with increasing DMSO concentration and decreasing temperature. On the other hand, water structure is found to be significantly deviated from tetrahedral arrangement in presence of DMSO clusters even at low temperature. The dynamics of water is also found to be considerably affected with increase of concentration and lowering of temperature. Similar phenomenon is observed for another amphiphilic molecule, ethanol, and has been discussed in chapter 5. Aqueous ethanol mixture is a widely studied solvent, both experimentally and using computer simulations. All the studies indicate several distinct salvation regimes. In recent molecular dynamics simulation studies, the reason for formation of micro-aggregates of ethanol is again attributed to percolation driven structural transformation. We carry out a temperature dependent study of water-ethanol binary mixture, particularly at low ethanol concentration to understand the molecular origin of such structural transformation. We find that the structural arrangement of ethanol as well as water molecules is similarly affected as that of DMSO with lowering of temperature. However, dynamics of water molecules in aqueous ethanol solution is found to be marginally affected, unlike the case of aqueous DMSO solution. We discuss the microscopic reason for such behaviour in a detailed manner. In Part III, we discuss the dynamics of linear polymer chains in different aqueous binary mixtures. Here we have three chapters. In chapter 6, we carry out a brief survey of the existing theories of polymers in solution. We discuss the quality of solvents depending on the preferred interactions between the polymer and the solvent or the polymer with its own. We also discuss the celebrated Flory-Huggins theory. We derive the expression of free energy of the Flory-Huggins theory in terms of the volume fraction of monomer and solvent molecules. In chapter 7, we discuss the results of our study of polymer dynamics in aqueous DMSO solution. We find that at a mole fraction 0.05 of DMSO (xDMSO ≈ 0.05) in aqueous solution, a linear polymer chain of intermediate length (n=30) adopts collapsed conformation as the most stable conformational state. The same chain exhibits an intermittent oscillation between the collapsed and the extended coiled conformations in neat water. Even when the mole fraction of DMSO in the bulk is 0.05, the concentration of the same in the first hydration layer around the polymer is found to be as large as 17 %. Formation of such hydrophobic environment around the hydrocarbon chain may be viewed as the reason for the collapsed conformation gaining additional stability. We find a second anomalous behaviour to emerge near xDMSO ≈ 0.15 that is attributed to the percolation driven structural aggregation of DMSO that lowers the relative concentration of the DMSO molecules in the hydration layer. In chapter 8, we carry out similar study of linear polymer chain in water– ethanol binary mixture. In this case also, we find a sudden collapse of the poly-merat xEtOH ≈ 0.05. Since ethanol molecules are known to form micro-aggregates in this concentration range, stability of collapsed state of polymer at this con-centration is anticipated to be correlated to this phenomenon. In fact, a purely hydrophobic polymer chain, in its collapsed form is anticipated to assist in the formation of spanning cluster comprised of hydrophobic ethyl groups at this concentration range thereby facilitating the percolation transition. We discuss these prospects in this chapter. Part IV deals with the solvent sensitivity to the conformational change and unfolding dynamics of protein. Part IV consists of five chapters. In chapter 9, we develop an understanding of protein folding and unfolding dynamics by discussing the fundamental theories developed in the last few decades. We also discuss the major role of solvents in stabilizing or destabilizing the native, ordered state. In chapter 10, we present a detailed study of unfolding of a small protein, chicken villin headpiece (HP36) in water-ethanol binary mixture, using molecular dynamics simulations. The prime objective of this work is to explore the sensitivity of protein dynamics towards increasing concentration of the cosolvent and unravel essential features of intermediates formed in the unfolding path-way. In water–ethanol binary mixtures, HP36 is found to unfold partially, under ambient conditions, that otherwise requires temperature as high as ∼ 600K to denature in pure aqueous solvent. The study unravels certain interesting aspects about the pathway of unfolding, guided by the formation of unique intermediates. Unfolding is initiated by the separation of hydrophoic core comprising three phenylalanine residues (Phe7, Phe11, Phe18). This separation initiates the melting of the helix2 of the protein. However, with an increase of cosolvent concentration different partially unfolded intermediates are found to be formed. We attribute the emergence of such partially unfolded states to the preferential solvation of hydrophobic residues by the ethyl groups of ethanol. We explore and subsequently quantify the detailed dynamics of unfolding in water-ethanol that appear to be more complex and sensitive to solvent composition. With an aim to develop a general understanding of the role of water–ethanol binary mixture in facilitating anomalous conformational dynamics of proteins, we carry out combined theoretical and experimental studies to explore detailed structural change of a larger protein, Myoglobin with increasing ethanol concentration. These studies are described in chapter 11. In agreement with our pre-vious observations, we identify in this case two well-defined structural regimes, one at xEtOH ≈ 0.05 and the other at xEtOH ≈ 0.25, characterized by formation of distinct partially folded conformations and separated by a unique partially unfolded intermediate state at xEtOH ≈ 0.15. We also find non-monotonic com-position dependence of (i) radius of gyration (ii) long range contact order (iii) residue specific solvent accessible surface area of tryptophan (iv) circular dichro-ism spectra and UV-absorption peaks. Multiple structural transformations, well-known in water-ethanol binary mixture, appear to have considerably stronger effects on the conformation and dynamics of protein Myoglobin. In chapter 12, we explore the free energy surface of unfolding pathway through umbrella sampling, for the small globular alpha-helical protein chicken-villin headpiece (HP36) in three different solvent conditions (water, xDMSO ≈ 0.15 and xDMSO ≈ 0.3). Recently established as a facilitator of helix melting, DMSO is found to be a good denaturant for HP36 and at a mole fraction of xDMSO ≈ 0.3, complete melting of the protein is ensured. The unfolding proceeds through initial separation or melting of the same aggregated hydrophobic core that com-prises three phenylalanine residues (Phe7, Phe11 and Phe18) accompanied by simultaneous melting of the helix2. Unfolding is found to be a multistage process involving crossing of three consecutive minima and two barriers at the initial stage. At a molecular level, Phe18 is observed to reorient itself towards other hy-drophobic grooves to stabilize the intermediate states. We identify the configuration of intermediates in all the solvent conditions which are found to be unique for the corresponding minima with similar structural arrangement. Consider-able softening of the barriers is observed with increasing DMSO concentration. Higher concentration of DMSO tunes the unfolding pathway by destabilizing the third minimum and stabilizing the second one, indicating the development of solvent modified, less rugged pathway. Chapter 13 provides a detailed microscopic mechanism of DMSO induced unfolding of HP36. We analyze the free energy contours of the protein HP36, obtained from molecular dynamics simulation in xDMSO ≈ 0.15 and xDMSO ≈ 0.3. The most probable intermediates obtained from the free energy contours are found to be similar to those obtained from umbrella sampling which again sup-ports the fact that the melting proceeds through formation of a series of unique intermediates. We characterize the preferential hydrophobic salvation of the hydrophobic core that drives the melting of secondary structure, by calculating time dependent radial distribution function and identifying the formation of strong orientation order between methyl groups of DMSO and phenyl alanine residues. Finally we employ Kramer’s rate equation to calculate the rate of bar-rier crossing that reveals significantly faster rate of unfolding with increasing DMSO concentration that is in agreement with simulation results. Whenever possible, we have discussed the scope of future work at the end of each chapter.

The research work is directed towards the investigation, optimization and application of some plant-based waste materials for the removal of some toxic trace metals (Cd, Pb and Mn) as well as selected oxyhalides (CIO3-,IO3- and BrO3-) in aqueous system. Waste materials from three plants; Athrixia philicoide, an indigenous bush tea; the outer covering peels of butternut Squash (Cucurbita Moschata) and pineapple (Ananas comosus) were evaluated for their sorption efficiency of the selected metals. batch and continuous experimental processes as well as conditions that might influence the sorption of the metals were investigated. These conditions include effects of pH sorption time, amount of adsorbent, volume of the aqueous medium, amount of metals etc. Qualitative and quantitative analysis of metal ions in solution was carried out using the ion chromatograph (IC) while the functional group identification present in waste materials was established using the Fourier Transform infr-red spectroscopy (FTIR), Quantitative biosorption equilibrium of 98.99% was reached within 6h at pH 6 and 100 ppm concentration of Pb metal with Athrixiaphilicoide under 30 min contact time. Applicability of the sorption process was tested on wastewater. Results revealed that > 99.93 %; 84.5 % and 64.3 % sorption efficiency was obtained for Mn, Cd and Pb respectively at pH 7 using Ananas Comosus adsorbent. For Athrixia philicoide, sorption efficiency from spiked wastewater ranged from 99.98 % for Cd; 99.96 % for Mn and 82.5 % adsorption for Pb at pH 7. For Juglans Cinerea, wastewater sorption efficiency varied between 78.76 %, 94.50 % and 96.50 % for Cd, Mn and Pb respectively at pH6. Results from the optimized method revealed the applicability of the method to environmental water samples. Possible large scale and industrial/commercial application of developed materials and methods would be explored. ) in aqueous system. Waste materials from three plants; Athrixia philicoide, an indigenous bush tea; the outer covering peels of butternut Squash (Cucurbita Moschata) and pineapple (Ananas comosus) were evaluated for their sorption efficiency of the selected metals. Batch and continuous experimental processes as well as conditions that might influence the sorption of the metals were investigated. These conditions include effects of pH, sorption time, amount of adsorbent, volume of the aqueous medium, amount of metals etc. Qualitative and quantitative analysis of metal ions in solution was carried out using the ion chromatograph (IC) while the functional group identification present in waste materials was established using the Fourier Transform infra-red spectroscopy (FTIR). Quantitative biosorption equilibrium of 96.99 % was reached within 6h at pH 6 and 100 ppm concentration of Pb metal with Athrixia philicoide under 30 min contact time. Cd and Mn adsorption by the same adsorbent under similar condition were less than 50 % for individual metal evaluation experiment. However, > 99 % adsorption was achieved with Cd in a mixture of the three (3) evaluated metals. Highest adsorption of 93 % of Pb was achieved with the Butternut Squash peel (Cucurbita moschata) at the optimal sorption pH of 6 followed by quantitative sorption of 99.2 % of Mn while Cd recorded a sorption level of 45 % all at 6 pH. The sorption efficiency of Pb, Cd and Mn using pineapple peels (Ananas comosus) also at the optimal sorption conditions of (pH 6, 30 min contact time and 100 ppm metal concentration) ranged from 98.7 %, 100 % and 99.90 % respectively. / Enviromental Science / M.Sc (Enviromental Science)

Les mousses aqueuses sont des fluides complexes constitués de dispersions concentrées de bulles de gaz dans une solution de tensioactifs. A l'instar d'autres fluides complexes comme les émulsions ou les pâtes, une mousse se comporte comme un solide viscoélastique lorsque la fraction volumique de la phase continue est suffisamment faible pour que l'empilement des bulles soit bloqué. Ses propriétés mécaniques résultent de couplages entre processus se produisant à plusieurs échelles de temps et d'espace : celles des tensioactifs adsorbés aux interfaces liquide-gaz, celles d'une bulle de gaz ou de mouvements collectifs à une échelle mésoscopique. A partir de trois expériences, nous avons mis en évidence l'impact du désordre de leur structure d'une part, et celui des tensioactifs d'autre part, sur les propriétés viscoélastiques des mousses. Nous avons mis au point un rhéomètre oscillatoire qui permet de mesurer la relation contrainte-déformation-fréquence d'une monocouche de bulles confinées entre deux parois planes parallèles tout en contrôlant sa pression osmotique. Nous avons montré que les relaxations de ces mousses de structure modèle sont pilotées par la rhéologie interfaciale de cisaillement que nous avons caractérisée indépendamment. Nous proposons un modèle quantitatif de ce couplage. Dans une deuxième expérience, nous avons sondé la réponse viscoélastique des mousses de structure 3D désordonnées. Nos résultats montrent que selon la rigidité des interfaces, le facteur de perte d'une mousse est décrit par une loi d'échelle en fréquence. Son évolution avec la taille des bulles et la viscosité du liquide permet de déterminer le mécanisme à l'origine de la dissipation. Dans une troisième expérience, Nous avons élaboré des mousses monodisperses de structure 3D ordonnées et de pression osmotique contrôlée. De manière remarquable, la variation de leur facteur de perte en fonction de la fréquence est similaire à celle des mousses désordonnées de même composition chimique. Ces résultats démontrent que le désordre de l'empilement des bulles n'est pas à l'origine des relaxations viscoélastiques linéaires des mousses, comme l'avaient suggéré plusieurs modèles théoriques, et ouvrent la voie à une modélisation quantitative du lien entre la viscoélasticité des interfaces et celle des mousses 3D / Aqueous foams are constituted of concentrated gas bubble dispersions in a surfactant solution. Like other complex fluids, such as emulsions or pastes, foam behaves as a viscoelastic solid if the volume fraction of the continuous phase is sufficiently small for the bubble packing to be jammed. The mechanical properties of the foam are due to couplings between processes at a wide range of time and length scales: The ones of the surfactant molecules that are adsorbed to the gas-liquid interfaces, the ones of the bubbles or collective motions at a mesoscopic scale. On the basis of three experiments, we have evidenced the impact of structural disorder and surfactant properties on foam viscoelasticity. We have constructed an oscillatory rheometer to measure the frequency and strain dependent stress response of a bubble monolayer confined between two parallel plates, subjected to an imposed osmotic pressure. We have shown that the relaxation of these model foams are governed by the interfacial shear rheology which we have probed in independent experiments and, we present a quantitative model of this coupling. In a second experiment, we have probed the viscoelastic response of disordered 3D foams. Our results show that, depending on interfacial rigidity, the mechanical loss factor of a foam is described by a scaling law depending on frequency. Its dependence on bubble size and liquid viscosity helps to determine the origin of the dissipation. In our third experiment, we have produced monodispersed ordered foams, subjected to a controlled osmotic pressure. Remarkably, the frequency scaling of their loss factor is similar to the one of disordered foams of the same chemical composition. These results demonstrate that the linear viscoelastic response of foams is not the consequence of disorder on the bubble scale as suggested by several previous theories, and they thus open the way for quantitative models linking the viscoelasticity of the interfaces to that of 3D foams

This thesis forms part of a project with the objective of developing and implementing a novel, wood-based, process for the industrial production of cellulose textile fibres. This new process should not only be cost effective but also have far less environmental impact then current processes. Natural and man-made fibres are usually plagued with problems (e.g. economic and environmental) and are unsuitable in meeting growing demands. The focus of this thesis was therefore to investigate the dissolution of cellulose derived from various pulps in novel aqueous solvent systems.             It was shown that cellulose could be dissolved in a NaOH/H2O solvent at low temperatures (<0°C) and that such an alkaline solvent can be improved regarding the solubility, stability and rheological properties of the cellulose dopes formed if different additives (salts or amphiphilic molecules) are used. The effect of different kinds of pretreatment (individually and combined) and the influence of pulp properties on cellulose accessibility and dissolution were also evaluated. These pretreatments affected, as expected, some characteristic properties of the pulps mainly by reducing the DP but also, for example, changing the composition of the carbohydrates. Not only did the pretreatment affect the solubility it also increased the stability of the cellulose dopes, resembling the effect of chemical additives to the NaOH system. According to multivariate data analysis it was established that, of the pulp properties analyzed, only the composition of carbohydrates and the DP had a significant influence on the solubility of the pulps used in this study. Finally, it was emphasized that the dissolution of cellulose pulps seemed to be controlled by a very complex interaction between both kinetic and thermodynamic parameters. / CelluNova

Liquid crystals are widely used in electronics, medicine and other fields. Analytical separations are important in the development of new liquid crystals to control the purity of synthesized substances. The sample analysis is important for detection of impurities formed during synthesis and for determination of chiral purity of the substance. Liquid crystal-forming substances cannot be separated by capillary zone electrophoresis due to the absence of readily ionizable groups. Electrokinetic chromatography is a method in which a suitable surfactant is added to the background electrolyte. The uncharged substances then interact with the electrically charged surfactant to obtain an effective charge. Separation can occur if they interact differently with the added surfactant. Another problem complicating the analysis is the very low solubility of analytes in water. Separations in this work were therefore carried out under non-aqueous conditions in acetonitrile. However, under these conditions a poor repeatability of the migration times of the substances was observed. Therefore, capillaries with differently coated inner walls were used in subsequent measurements. Surface modification should improve the repeatability of migration times. Several types of capillary coating have been tested. Dynamic coating...

Neste trabalho estudou-se a modelagem termodinâmica do equilíbrio de fases de sistemas aquosos bifásicos formados por um polímero neutro, especificamente o poli(etileno glicol), e um sal. O modelo implementado é baseado na equação de Pitzer para soluções de eletrólitos, dele diferindo ao considerar a influência das propriedades do polímero no cálculo da constante dielétrica e da densidade do meio, presentes no cálculo do termo relativo às interações de longo alcance da energia de Gibbs excedente. Além disso, procurou-se também considerar a dependência dos parâmetros relativos ao polímero com respeito ao tamanho de sua cadeia. Dados experimentais obtidos da literatura foram utilizados para a obtenção dos parâmetros ajustáveis do modelo, em cuja implementação foi utilizada a linguagem FORTRAN. A alteração nas propriedades do meio modificou o estado de equilíbrio calculado, fato que pôde ser observado por meio da análise de fatores como o desvio entre a composição calculada pelos modelos e os valores experimentais em cada fase e a inclinação da linha de amarração. Em alguns sistemas o desempenho do modelo modificado foi superior nesses parâmetros, mas em termos gerais a modificação no cálculo da constante dielétrica e da densidade não resultou em melhora no cálculo do equilíbrio de fases, por vezes piorando-o, de modo que investigações específicas sobre o termo de longo alcance foram conduzidas para verificar a razão deste comportamento. A inclusão de parâmetros ternários aumentou a capacidade de correlação de ambos os modelos. No que diz respeito à possibilidade de correlação dos parâmetros de interação como função do tamanho da cadeia polimérica, que poderia levar a um modelo preditivo, observou-se que somente para tamanhos grandes de cadeia foi possível estabelecer uma dependência direta e inequívoca. / The thermodynamic modeling of phase equilibrium in aqueous two phase systems containing the neutral polymer poly(ethylene glycol) and a salt was studied in this work. The implemented model is based on the Pitzer equation for electrolytes solutions, modified in order to account for the influence of polymer properties in both the medium dielectric constant and the medium density, values which are present in long range term of the excess Gibbs energy. The dependence of the adjustable parameters on the polymer molecule size was also investigated. Experimental data from literature were used to obtain the adjustable parameters of the model, in whose implementation the FORTRAN computer language was used. The changes introduced into the long range term resulted in a shift of the calculated equilibrium compositions, which could be observed by analyzing the deviation between calculated and experimental compositions and tie-line slopes. For some systems the performance of the modified model was superior, but in most cases the changes introduced did not result in a significant improvement in phase equilibrium calculations, and even worsened them. Specific investigations on the long range term were carried out to verify the reason for such behavior. The insertion of ternary parameters increased the correlation capacity of both models. Concerning the hypothesis that the interaction parameters can be directly related to the polymer chain size, which might eventually lead to a predictive model, it was noticed that a direct dependency holds only for larger chain sizes.

Foram sintetizadas duas séries de tensoativos catiônicos de estruturas gerais RCONH(CH2)2-N+(CH3)3 Cl- e RCONH(CH2)2-N+(CH3)2-CH2-C6H5 Cl-, sendo RCO uma cadeia acílica contendo 10, 12, 14 e 16 átomos de carbono. Estes tensoativos foram sintetizados pela reação do ácido carboxílico puro com N,N-dimetiletilenodiamina resultando na amidoamina correspondente. A quaternização desta última foi feita pela reação com cloreto de benzila ou com iodeto de metila. Os iodetos foram convertidos nos correspondentes cloretos por troca-iônica. A localização média da interface micelar e a conformação do grupo hidrofílico na micela foram investigadas por IV e RMN. A adsorção na interface solução-ar e a micelização foram estudadas por diversas técnicas: calorimetria, condutância, FEM (força eletromotriz), IV de FT, RMN e tensão superficial. Os resultados foram comparados com os de tensoativos catiônicos comuns, como R\'N+(CH3)3R\" Cl-, sendo R\' = grupo alquílico contendo de 10 a 16 carbonos e R\" = um grupo metila ou benzila. A adsorção e a micelização dos tensoativos contendo o \"espaçador\" (CONH-CH2-CH2) são mais favoráveis. Os valores de ΔGºads e ΔGºmic mais negativos para estes tensoativos, refletem principalmente a transferência mais favorável do grupo polar da solução aquosa para a interface solução/ar e/ou para a micela. Isto ocorre devido à formação de ligações de H, diretas e/ou via água, entre os grupos amida dos monômeros de tensoativo na interface e micela. As diferenças nos valores de ΔGºcabeça+CH3 dos tensoativos com e sem o grupo amida na adsorção (ΔΔGº ads cabeça+CH3 = -17.2 kJ mol-1) e micelização (ΔΔGº ads cabeça+CH3 = -5 a -7 kJ mol-1) estão de acordo com a energia de ligações de H fracas. Os resultados de IV de FT e RMN de 1H comprovaram a formação destas ligações de H e indicaram que a carbonila está presente na interface e o grupo benzila está voltado para o interior da micela. / Two series of cationic surfactants have been synthesized: benzyl-(2acylaminoetil) dimethylammonium chlorides, RCONH(CH2)2-N+(CH3)3 Cl-, and (2-acylaminoethyl)dimethylammonium chlorides, RCONH(CH2)2-N+(CH3)2-CH2-C6H5 Cl-, where RCO refers to an acyl group with 10, 12, 14 and 16 carbon atoms. These surfactants were obtained by reacting chromatographically pure carboxylic acids with N,N-dimethylethylenediamine to give an intermediate amidoamine. The latter was quaternized with benzyl chloride or methyl iodide. Surfactants with iodide counter-ion were transformed into the corresponding chlorides by ion exchange on a macro-porous resin. The average position of micellar interface and conformation of the headgroup were studied by FTIR and NMR. A multi-technique approach has been employed in order to study the effects of the presence of the \"spacer\" group (-CONH- CH2-CH2) on the adsorption and aggregation of these surfactants. The techniques employed were: calorimetry, conductance and EMF measurements, FTIR, NMR, surface tension, and Iight scattering. Surfactants with the spacer group (CONH-CH2-CH2) have more favorable Gibbs free energies of adsorption and/or micellization due to the more favorable transfer of the head-group from bulk phase to the interface and/or the micelle. This is attributed to the formation of direct, and/or water-mediated H-bonding between the surfactant amide groups. Differences in values of ΔGºHead-group+CH3 of surfactants with and without spacer group (ΔΔGº ads Head-group+CH3 = -17.2 kJ mol-1 and ΔΔGº ads Head-group+CH3 = -5 a -7 kJ mol-1 for adsorption and/or micellization, respectively) are in agreement with weak hydrogen bonding. Additional evidence for H-bond formation and for the (average) conformation of the benzyl head-group in the micelle was provided by FTIR and NMR data. The former showed that the amide group is highly hydrated, whereas the latter showed shielding/deshielding of the methylene groups of the surfactant hydrophobic tail, in agreement with a conformation in which the benzyl group is \"bent\" toward the micellar interior.