The aim of this thesis is to study the structural and thermodynamical properties of polymers at liquid/liquid interfaces by means of multiscale molecular dynamics simulations. This thesis is presented in alternative format, and the results, consisting of three journal articles, are divided into two main parts. The first part of the thesis looks at the structural and dynamical changes as well as the thermodynamic stability of polymers of varying topology (linear and star-shaped) at interfaces by performing molecular dynamics simulations on model systems. It was found that homopolymers are attracted to the interface in both good and poor solvent conditions making them a surface active molecule, despite not being amphiphilic. In most cases changing polymer topology had only a minor effect on the desorption free energy. A noticeable dependence on polymer topology is only seen for relatively high molecular weight polymers at the interface. Examining separately the enthalpic and entropic components of the desorption free energy suggests that its largest contribution is the decrease in the interfacial free energy caused by the adsorption of the polymer at the interface. Furthermore, we propose a simple method to qualitatively predict the trend of the interfacial free energy as a function of the polymer molecular weight. In terms of the dynamics of a linear polymer, the scaling behaviour of the polymer confined between two liquids did not follow that predicted for polymers adsorbed onsolid or soft surfaces such as lipid bilayers. Additionally, the results show that in the diffusive regime the polymer behaves like in bulk solution following the Zimm model and with the hydrodynamic interactions dominating its dynamics. Further simulations carried out when the liquid interface is sandwiched between two solid walls show that when the confinement is a few times larger than the blob size the Rouse dynamics is recovered. The second part of the thesis focuses on optimizing the MARTINI coarse-grained (CG) Model, which retains certain chemical properties of molecules, to reproduce solubility of polymers, in specific polyethylene oxide (PEO), in both polar and non-polar solvents. Performing molecular dynamics simulations using this CG model will then enable us to study the properties PEO in octanol/water and hexane/water systems with increased length and timescales not accessible by atomistic simulations. The MARTINI CG method (Marrink et al., J. Phys. Chem. B, 2007, 111, 7812) is based on developing the optimal Lennard-Jones parameters to reproduce the partition free energy between water (polar solvent) and octanol (apolar solvent). Here we test the MARTINI CG method when modelling the partitioning properties of PEO, with increasing molecular weight between solvents of different polarity by comparing the results with atomistic simulation. We show that using simply the free energy of transfer from water to octanol to obtain the force parameters does not guarantee the transferability of the model to other solvents. Instead one needs to match the solvation (or hydration) free energies to ensure that the polymer has the correct polarity. We propose a simple method to select the Lennard-Jones parameter to match the solvation free energies for different beads. We also show that, even when the partition coefficient of the monomer is correct, even for modestly high molecular weight of the polymer the predicted partitioning properties could be wrong.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / In the process of purification of biodiesel is of extreme importance washing methyl or ethyl ester rich- phase, since in conventional processes there is a great amount of water. During the washing is extracted primarily excess alcohol. Composition data for the washing process of biodiesel is still scarce in the literature and the study of liquid-liquid equilibrium provides the means to develop equipment and to optimize the extraction processes. Thus the main goal of this work is to determine equilibrium data for three different ternary systems: water - methanol - soybean biodiesel; corn biodiesel â methanol â water; methanol - coconut biodiesel - water at 20  C and 40  C. The experiments were carried out in equilibrium cells where the temperature was kept constant by thermostat control. The experimental determination was made by the method of densimetry. The consistency of data obtained for the tie lines was verified by correlations. It was verified by the ternary graphs, little influence of temperature on the systems studied. The equilibrium data were correlated liquid-liquid models for the activity coefficient NRTL, UNIQUAC and UNIFAC and proved quite satisfactory. / No processo de purificaÃÃo do biodiesel, a lavagem da fase rica em metil ou etil Ãster à de extrema importÃncia, visto que nos processos convencionais hà um grande gasto de Ãgua. Durante a lavagem à extraÃdo principalmente Ãlcool em excesso. Dados de composiÃÃes para a lavagem de biodiesel ainda sÃo escassos na literatura e o estudo do equilÃbrio lÃquido-lÃquido pode fornecer meios para o desenvolvimento de equipamentos e otimizaÃÃo dos processos de extraÃÃo. Dessa forma, o principal objetivo dessa dissertaÃÃo foi determinar dados de equilÃbrio lÃquido- lÃquido para os sistemas ternÃrios contendo biodiesel de soja + metanol + Ãgua, biodiesel de milho + metanol e Ãgua e biodiesel de coco + metanol + Ãgua, a 20 ÂC e 40 ÂC. Os experimentos foram feitos em cÃlulas de equilÃbrio mantendo a temperatura constante. A determinaÃÃo experimental das misturas ternÃrias foi feita pelos mÃtodos de titulaÃÃo e densimetria. A consistÃncia dos dados das linhas de amarraÃÃo foi verificada pelas correlaÃÃes de Othmer-Tobias e Hand. Verificou-se por meio de grÃficos ternÃrios, pouca influÃncia da temperatura sobre os sistemas estudados. Os dados de equilÃbrio lÃquido-lÃquido foram correlacionados pelos modelos para coeficiente de atividade NRTL, UNIQUAC e UNIFAC e mostraram-se bastante satisfatÃrios.

Orientador: Martin Aznar / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-11T20:46:38Z (GMT). No. of bitstreams: 1 Cunha_EvelynVilmaCaravazi_M.pdf: 1619492 bytes, checksum: 1e4afeecf37b0da40904e4da5be5eb20 (MD5) Previous issue date: 2008 / Resumo: Neste trabalho são determinados experimentalmente dados de equilíbrio líquido ¿ líquido dos sistemas de duas fases aquosas, água + PEG 8000 + sulfato de magnésio e água + PEG 8000 + sulfato de sódio, nas temperaturas de 25 e 50ºC. As composições de ambas as fases em equilíbrio foram obtidas por gravimetria, utilizando a técnica de liofilização (freeze-drying) para a determinação da quantidade de água e a calcinação em forno mufla para quantificação de PEG, sendo que a composição de sal foi obtida por diferença de massa. Os dados assim obtidos foram modelados através dos modelos NRTL e UNIFAC para o cálculo do coeficiente de atividade. O modelo NRTL, com a estimação de novos parâmetros de interação energética entre as espécies envolvidas, apresentou excelentes resultados de correlação, com baixos desvios entre as composições experimentais e as calculadas. O modelo UNIFAC, que é basicamente preditivo, foi capaz de representar satisfatoriamente os sistemas estudados com alguns grupos funcionais e parâmetros de interação existentes na literatura e outros estimados a partir dos dados experimentais obtidos nesse trabalho / Abstract: In this work, experimental data of the liquid-liquid equilibrium for the aqueous twophase systems water + PEG8000 + magnesium sulfate and water + PEG8000 + sodium sulfate were determined at 25 e 50°C. The compositions of both equilibrium phases were obtained by a gravimetric method, using the lyofilization (freeze-drying) technique for the water determination and the calcination in a muffle furnace for the PEG determination; in this way the salt was determined by mass difference. The experimental data were modeled by the NRTL and UNIFAC models for the activity coefficient. The NRTL model, with new energy interaction parameters, showed excellent correlation results, with low deviations between experimental and calculated compositions. The UNIFAC model, which is a predictive one, was able to represent the studied systems with some energy interaction parameters form the literature and others estimated from the experimental data determined in this work / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Orientador: Elias Basile Tambourgi / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-04T03:58:27Z (GMT). No. of bitstreams: 1 Leite_PatriciaBernardi_D.pdf: 6148337 bytes, checksum: f4db900db28f697e2c296bf0ea5251a1 (MD5) Previous issue date: 2005 / Resumo: : A enzima glicose-6-fosfato desidrogenase (G6PDH) pode ser obtida de origem animal, vegetal ou microbiana, como no caso da levedura Saccharomyces cerevisiae. Esta enzima apresenta grande importância para a sobrevida celular uma vez que participa da regulação do ciclo das pentoses sendo responsável pela manutenção de um nível adequado de NADPH nas células. A deficiência de glicose-6-fosfato desidrogenase (G6PDH) em seres humanos é considerada a mais importante enzimopatia diagnosticada. A deficiência desta enzima favorece a ruptura de membrana dos glóbulos vermelhos (hemácias ou eritrócitos) levando à anemia hemolítica. Nesse trabalho, estudou-se as condições de extração da enzima G6PDH através do uso da técnica de extração líquido-líquido por micelas reservas de tensoativos aniônicos (AOT) e catiônicos (CTAB). Planejamentos estatísticos específicos para casa sistema analisado foram empregados. As variáveis estudadas foram pH, concentração do tensoativo e temperatura. Estudou-se, também uma microcoluna agitada por campânulas pulsadas, visando promover um eficiente contato entre as fases através de uma agitação suave, aumentando assim o tempo de contato entre as fases no interior da microcoluna e também evitando a desnaturação da enzima. As porcentagens de recuperação da enzima para estes sistemas variaram de nulos a 5,10% utilizando AOT e de nulos a 14,04% cin CTAB. No entanto, observou-se diminuição na atividade catalítica da enzima ...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: The enzime glucose-6-phosphate dehydrogenase (G6PDH) it can be obtained of animal origin, vegetable or microbial, as in the case of the yeast Saccharomyces cerevisiae. This enzymes presents great importance for the cellular survival once it participates in the regulation of the cycle of the pentosys being responsible for the support of an appropriate level of NADPH in the cells. The deficiency of the glucose-6-phosphate dehydrogenase (G¨PDH) in human being the most important diagnosed enzymepatic is considered. The deficiency of this enzyme favors the rupture of the membrane of the red globules (hemacys or erythrocytes), taking to the hemolytic anemia. In this work, it was studies the conditions of extraction of the enzyme G6PDH by extraction on reserved micelles utilizing a anionic surfactant (AOT) and cationic surfactant (CTAB). Specific statical design for each analyzed system were used. The studied variables were: pH, concentration of the surfactant and temperature. It was studied, also, a microcolumn agitated by pulsed caps, due to promote an efficient contact between the phases in the column and also to avoid the enzyme denaturation and the loss of main proteins properties. The percentages of recovery of the enzyme of these system varied of 0 to 5,10% using AOT and of 0to 14,04% with CTAB. However, decrease was observed in the catalytic activity of the enzyme ...Note: The complete abstract is available with the full electronic digital thesis or dissertations / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

Submitted in fulfilment of the academic requirements of Masters in Applied Sciences (Chemistry), Durban University of Technology, 2017. / This thesis forms part of the Durban University of Technology Thermodynamics Research Unit’s project which is aimed at developing a method for determination of the liquid-liquid equilibria (LLE) data for the azeotrope {methanol + water} with an ionic-liquid (IL) using DSA5000M to assess the efficiency of the ionic liquid to be used in liquid-liquid extractions for the recovery and recycling of methanol from petroleum refinery. The objective of this study was to determine the liquid-liquid equilibria data of the azeotrope {methanol + water} using 1-ethyl-3-methylimidazolium ethyl sulfate ionic liquid with the intention to recycle methanol from the Fischer-Tropsch (FT) process by- products in petroleum industries and to utilize it in gasoline additives in a new methanol to gasoline (MTG) petroleum process. LLE studies of systems containing alcohols and water are important due to the increasing demands of oxygenated compounds to produce lead free gasoline. Light alkanols such as methanol and ethanol are reported to be suitable compounds in order to produce lead free gasoline, but the use of methanol in gasoline blends can cause phase separation problems in: 1. dry conditions, these are due to its partial solubility in saturated hydrocarbons. 2. the presence of water from ambient humidity or in storage tanks, this depend on unfavourable distribution factor between aqueous and the hydrocarbon phase. To determine the possibility of separating methanol from water using ionic liquid, the liquid-liquid equilibria data was determined at room temperature, T = 298.15 K and atmospheric pressure to investigate whether it separate from water and/or a non-phase separation if it is used as an additive. The experimental data generated was compared to that of the literature for the system {methanol (1) +toluene (2) + dodecane (3)} and showed good agreement with the literature data with only maximum deviation of ± 0.0015 in the mole fraction using density calculations and ± 0.0092 in the mole fraction when using refractive index calculations The selectivities and distribution coefficients for this system were also calculated and the maximum deviation between the two methods (nD and ρ) was ± 1.33 in selectivities and found to be ±0.001 for distribution coefficients. The maximum deviation in distribution coefficients from literature when using nD calculations for system 1 was ±0.04 and ±0.01 for ρ. For the selectivity values the deviation from that of literature of nD when compared was found to be ± 1.28 and 0.29 for ρ respectively. The selectivity values from the density calculations were found to be in the range 2.82 – 7.66 for this system with the distribution coefficient values reported in the range 0.17 – 0.23. In the second system (system 2) the generated experimental data was also compared to that of the literature for the system {water (1) + methanol (2) + cyclohexane (3)} and in good agreement with literature values with only maximum deviation of ± 0.0091 in the weight fraction based on density calculations. The selectivities and distribution coefficients were also calculated and the maximum deviation between the literature and the experimental data was computed to be at ± 0.0003 for selectivity and ±0.09 in distribution coefficient. The selectivity values were found to be in a range 0.00 - 0.04 for this system and were constant throughout the phases but significantly less than one; with the distribution coefficient values in the range 0.00 – 0.008. For 1-ethyl-3-methylimidazolium ethyl sulfate system (Ionic liquid system) the selectivity values were not constant throughout the two-phase region and the values were found to be in the range 0.63 -0.99 still below one which indicates that the ionic liquid used in this study could not be considered as a potential solvent for the separation of the investigated azeotrope. The distribution coefficients for this system were determined and found to be in the range 0.23 – 0.74. The certainty and reliability of experimentally measured tie-line data was ascertained by applying Othmer-Tobias (OT) correlations and the Non-Random, Two Liquid (NRTL) parameters. The OT correlations for system 1 was linear and indicated the certainty of the five tie-lines prepared for this system. In system 2 the OT correlation was not linear and indicated extensively high errors as well as high systematic multiplicative and additive errors in calculations of mole fractions. For the IL system the OT correlation was linear throughout the whole tie-line range and indicated the adequate precision, which denotes that the investigation was carried out with minimal random and systematic errors and indicated the efficiency of the DSA 5000 M to generate the liquid-liquid equilibria data. All the ternary systems were well correlated and in good agreement with the estimated NRTL data. It was only system 1{methanol (1) + toluene (2) + dodecane (3)} that gave a high maximum deviation ( %RSMD) of 1.288 when using the RI measurements with the minimum error margin of 0.6320, this account as to why RI measurements were not applied in other systems (system 2 and ionic liquid system). Similarly for the same system; system 1{methanol (1) + toluene (2) + dodecane (3)} when using the density measurements; the NRTL model gave a maximum deviation of 0.5620 and minimum error margin of 0.2590. The NRTL obtained for system 2 {water (1) + methanol (2) + cyclohexane (3)} gave the maximum deviation of 0.5752 and minimum error margin of 0.0127. The NRTL for the ionic liquid ternary system {[EMIM][EtSO4](1) + methanol (2) + water (3)}showed a good agreement between the experimental data and the NRTL model tie- line data with the %RSMD of 1.0201 on the upper limit and 0.1620 as a lower deviation. / M

A fundamental challenge for liquid-liquid separation techniques such as countercurrent chromatography (CCC)and centrifugal partition chromatography (CPC), is the swift, efficient selection of the two phase solvent system containing more than two solvents, for the purification of pharmaceuticals and other molecules. A purely computational model that could predict the optimal solvent systems for separation using just molecular structure would be ideal for this task. The experimental value being predicted is the partition coefficient (Kd), which is the concentration of the compound in one phase divided by the concentration in the other. Using this approach, Quantitative Structure Activity Relationship (QSAR) models have been developed to predict the partitioning of compounds in two phase systems from the molecular structure of the compound using molecular descriptors. A Kd value in the range of 0.5 to 2 will give optimal separation. Molecular descriptors are varied, examples include logP values, hydrogen bond donor values and the number of oxygen atoms. This work describes how the QSAR models were developed and tested. A dataset of experimental logKd values for 54 compounds in six different combinations of four solvents (heptane, ethyl acetate, methanol and water) was used to train the QSAR models. A set of 196 possible molecular descriptors was generated for the 54 compounds and a partial least squares regression was used to identify which of these was significant in the relationship between logKd and molecular structure. The resulting models were used to predict the logKd values of four test compounds that had not been used to build the QSAR models. When these predictions were compared to the experimental logKd values, the root mean squared error for four of the six models was less than 0.5 and less than 0.7 for the remaining two. These models were used to successfully separate a range of structurally diverse pharmaceutical compounds by predicting the best solvent systems to carry out the separation on the CCC/CPC using nothing but their molecular structure.

The ternary phase behaviour of the n-heptane-l-propanol-water system was studied and compared with the theoretical prediction based on the UNIQUAC model for non-electrolyte solutions. The results showed that this model adequately approximated experimental studies. The excess enthalpies and excess volumes for several binary mixtures were determined. The excess enthalpies were measured using a LKB flow microcalorimeter and the excess -volumes determined using a PAAR densitometer. The study showed that no significant enthalpy or volume changes occurred when petrol/n-heptane were mixed with alcohols . Ternary phase diagrams, including tie lines have been determined for a number of petrol-alcohol-water systems (including the Sasol blend of alcohols). The tie line results show that the concentration of water in the water-rich layer is strongly dependent on the type of alcohol used. The Sasol alcohol blended with petrol resulted in a high water concentration in the water-rich layer which forms on phase separation. This is believed to contribute significantly to the corrosion problems experienced by motorists using the Sasol blended fuel on the Witwatersrand. The effect of temperature on several of these blends was included in the study. Diesel-alcohol blends and the co-solvent properties of ethyl acetate investigated. Ethyl acetate ensures miscibility at low concentrations for diesel-ethanol blends. Octyl nitrate and two cetane improvers from AECI were assessed in terms of their ability to restore cetane rating of blended diesel fuel to that of pure diesel fuel. The results indicated that all three samples were successful in this application. / KMBT_363

The dispersion of graphene in 1,2-dichloroethane (DCE), its subsequent attachment at the water-DCE interface and the reduction of oxygen at the water-DCE interface proceeding via interfacial graphene have been investigated. Using addition of an electrolyte which screens surface charge, it was found that electrostatic repulsions play a significant role in determining the kinetic stability of lyophobic non-aqueous graphene dispersions. The onset of aggregation was determined and it was found that dispersions prepared from higher-oxygen content graphite were more stable than those prepared from lower-oxygen content graphite, indicating that oxygen content is important in determining the surface charge on graphene in non-aqueous dispersion. The presence of organic electrolyte was also found to promote assembly of graphene into a coherent film at the liquid-liquid interface. Measurement of the liquid-liquid interfacial tension and three-phase contact angle revealed that the energetics of particle attachment did not change in the presence of organic electrolyte, thus indicating a mechanism of inter-particle electrostatic repulsion minimisation through surface charge screening. Interfacial graphene was found to display a catalytic effect toward the oxygen reduction reaction at the water-DCE interface. A bipolar cell was developed which showed that this reaction occurs heterogeneously, with graphene acting as a conduit for electrons across the water-DCE interface.

Supercapacitor electrodes were fabricated at a high active mass loading and exhibited enhanced electrochemical capacitance. A conceptually new salting-out extraction processing technique for the synthesis of dispersed Mn3O4-carbon nanotube (CNT) nanocomposites was developed, alleviating the need for hydrophobic solvents. The choice of isopropyl alcohol and NaCl for the extraction process offer advantages of an easy upscaling of this process. The salting out technique was shown to work with Octanohydroxyamic acid (OHA) and Lauryl Gallate (LG) as extractors and dispersants, critical to the success of the extraction. Mechanisms for surface adsorption on Mn3O4 and CNT for both OHA and LG are discussed. A secondary project was also undertaken, to investigate the use of chlorogenic acid and 3,4,5 – trihydroxybenzamide, as co-dispersing agents for MnO2 and CNTs. These molecules are used due to their unique structural properties, which are discussed. The electrodes fabricated using these co-dispersants showed significant increases in their specific capacitances and SEM imaging indicated improved mixing, compared to samples prepared without dispersants. A specific capacitance of 6.5 F g-1 was achieve at low electrical resistance, attributed to the microstructure of electrodes prepared with the co-dispersant molecules. / Thesis / Master of Applied Science (MASc) / The ever-growing realization that our energy consumption as a civilization is not sustainable, has fueled people around the globe to imagine and design new methods of energy storage, in attempts to mitigate this issue. From the foundational works of scientists, it has become clear to see that there is not “one right answer”. Instead, the unique benefits and drawbacks of energy storage technologies should be balanced and applied in situations where their properties permit a high efficacy. The intention of this work is to assist in the development of new materials to be used for energy storage devices called electrochemical supercapacitors. Novel colloidal processing techniques were developed, leading to the fabrication of high-performance electrodes, and providing further insight to the structure-properties relationship of organic extractors and co-dispersing agents for the design of nanocomposites.

Biodiesel is produced from vegetable oils through transesterification. Triglyceride mixtures extracted from oilseed feedstocks are upgraded by reaction with an alcohol in the presence of a catalyst to produce fatty acid esters. This reaction produces a mixture of esters, glycerin, alcohol, and catalyst. Separation of the fatty acid esters (biodiesel) and glycerin can be accomplished through liquid-liquid extraction by water addition. Designing liquid-liquid extraction with water as the solvent requires ternary liquid-liquid equilibrium data for mixtures of water, glycerin, and fatty acid esters. Ternary mixture LLE data have been experimentally measured for several of these systems. Those measured include mixtures with the methyl esters of lauric, myristic, palmitic, stearic, and oleic acids. Data were collected at atmospheric pressure and 60°C. These ternary systems have been correlated using the NRTL equation. These data and correlation parameters can be used to improve separations efficiency in trans-esterified biodiesel fuels.