Basel, Math.-naturwiss. Diss., 1921. / Aus: Zeitschrift f. anorgan. u. allgem. Chemie. Bd 121, H. 2., 1922

No description available.

Many important atmospheric processes are determined by the chemical composition of aerosols, including organic material. Dicarboxylic acids are a commonly detected class of organic material in urban, rural, and remote sites across the globe. Understanding the surface behavior of these molecules is imperative in characterizing the atmospheric fate of these molecules in aerosols, especially at an aerosol surface. In fact, little is known about their orientation, solvation, or pH dependence. This dissertation explores in molecular level detail the concentration and pH behavior of low molecular weight dicarboxylic acids at the air/water interface, which is used as a model for an aerosol surface. The solvation of the carboxylic head groups is shown to be dependent upon the length of the alkyl backbone. Indeed, the solvation of the head groups changes dramatically from very weakly solvated to typical surface solvation to near bulk solvation as the backbone increases. The orientation and conformation at the surface is fully explored to explain these differences in solvation. The pH dependence of surface adsorption is characterized, and it is shown that some acids are only surface active if they are fully protonated while others may still be surface active in singly or fully deprotonated forms. Using a combination of vibrational sum frequency spectroscopy (VSFS), surface tension, and computational modeling, the behavior at the air/water interface of four of the most relevant surface-active dicarboxylic acids (malonic, succinic, glutaric, and adipic acid) is completely described. VSFS, a surface specific optical technique, provides details about the solvation, orientation, and number density at the surface while surface tension measurements provide corollary information about the surface density. The use of computational modeling aids and confirms the spectral analysis while also providing molecular level details about the surface adsorption of the acids studied. By investigating the concentration and pH dependence of these molecules, molecular level detail is obtained which enables a complete description of these acids at an air/water interface and provides pertinent surface information on these atmospherically important organic molecules. This dissertation includes both previously published and unpublished co-authored material.

Dispersing co-crystals in a polymeric carrier may improve their physicochemical properties such as dissolution rate and solubility. Additionally co-crystal stability may be enhanced. However, such dispersions have been little investigated to date. This study focuses on the feasibility of dispersing co-crystals in a polymeric carrier and theoretical calculations to predict their stability. Acetone/chloroform, ethanol/water, and acetonitrile were used to load and grow co-crystals in a HPMCAS film. Caffeine-malonic acid and ibuprofennicotinamide co-crystals were prepared using solvent evaporation method. The interactions between each of the co-crystals components and their mixtures with the polymer were studied. A solvent evaporation approach was used to incorporate each compound, a mixture, and co-crystals into HPMCAS films. Differential scanning calorimetry data revealed a higher affinity of the polymer to acidic compounds than their basic counterparts as noticed by the depression of the glass transition temperature (Tg). Moreover, the same drug loading produced films with different Tgs when different solvents were used. Solubility parameter values (SP) of the solvents were employed to predict that effect on the depression of polymer Tg with relative success. SP values were more successful in predicting the preferential affinity of two acidic compounds to interact with the polymer. This was confirmed using binary mixtures of naproxen, flurbiprofen, malonic acid, and ibuprofen. On the other hand, dispersing basic compounds such as caffeine or nicotinamide with malonic acid in HPMCAS film revealed the growth of co-crystals. A dissolution study showed that the average release of caffeine from films containing caffeine-malonic acid was not significantly different to that of films containing similar caffeine concentration. The stability of the caffeine-malonic acid co-crystals in HPMC-AS was prolonged to 8 weeks at 95% relative humidity and 45°C. The theory developed in this project, that an acidic drug with a SP value closer to the polymer will dominate the interaction process and prevent the majority of the other material from interacting with the polymer, may have utility in designing co-crystal systems in polymeric vehicles

E-glass has been widely used as a reinforcing material for years, especially as a plastic reinforcer in the production of GRP (Glass Reinforced Plastic). Failure of GRP materials under stress came in to the picture quite recently. Since then studies have been conducted in an attempt to understand the causes and the underlying behaviour. / Except for the last section of the research (analysis using a kinetic approach) where glass fibre was cut out to weigh approximately 1.0g, standard sized specimens were soaked in the required acid solutions of desired concentrations for varying temperatures and time frames. Wherever tensile strength retention was measured, LLOYD instrument was employed. Leaching of the cations were analysed using Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES and also know and ICP-AES). / The scope of this project can be divided in to four sections; first section involved investigating the effects of malonic acid. The study of malonic acid was narrowed to investigating the trend in strength retention. A rapid strength loss was observed initially followed by a much steady decline in the strength. However the continuation of the loss of strength was unmistakable throughout the time period of exposure. Furthermore, temperature can be observed as a facilitating factor in this degradation reaction. / Secondly the corrosive effect of glyoxylic acid on E-glass fibre was studied. This was explored at two different temperatures for two specific time frames using various concentrations of the acid of interest. The influence of this acid on the glass fibre was found out in terms of strength retention and loss of cations from the glass matrix. The mildness of this acid was accentuated by the fact that 70% or more of the strength was retained at all the conditions employed. A minima in strength retention was observed at 2M acid concentration similar to the trends observed in the past (Betz and Jones 2003 and Jones and Chandler 1986). Leaching of cations reflected this trend. The large strength retention could be related to the fewer amounts of Ca and K leached from the glass matrix (Kumosa and Qui, 1997). Similar to malonic acid, an unusually large amount of B was leached out that could be due to the favourable orientation of the anion with the trivalent ions during the complex formation. Yet again temperature was found to enhance the degradation process. / Next the extent of passivation (if any) showed by malonic acid was investigated using E-glass fibre pre-treated in 5M malonic acid and post treated in known corrosive acids hydrochloric acid and oxalic acid. Passivation of malonic acid was put to test through examination of strength retention of the fibres under these conditions. This segment was carried out as an extension of a finding (a behaviour synonymous to passivation) shown by malonic that surfaced the previous year by the present researcher. Increasing the pre-treatment time showed a great improvement in the retained strength for all the post-treatment acid mediums. Furthermore, while Jones and Betz (2004) featured 20-40% strength retention within a short time frame in 3M HCl, the immense amount of strength retention (60-70%) preceding pre-treatment should definitely be noted. Similarly strength retention of about 80% was observed when post-treated with the severely corrosive oxalic acid. Hence its is clear that passivation can be induced through prolonged pre-treatment in 5M malonic acid that could inhibit the attack of corrosive acid at least for a period of time. / The last fragment of the study focussed on understanding and working out the mechanism behind the reactions between the E-glass fibre and acid medium in terms of kinetics. The acids utilized were 1.5M malonic acid and 3M glyoxylic acid and the assessments were made through the analysis of the weight changes brought about by the acid medium at various temperatures and time frames. In addition leaching patterns of cations were evaluated as this could contribute in achieving the objective. Maximum weight loss reached 4% in glyoxylic acid while that for malonic acid exceeded 20%. The general trend was that the glass fibres lost weight in both acids for a period of time followed by an evident weight gain. Furthermore the weight loss results fit the first order rate law. While the leaching of cations reflects the weight loss for the shorter time frames, steady loss of ions was visible even for the longer time frames where the weight has increased. The weight gain could be explained in terms of binding of anions to certain cations on the glass surface, accounting for the hindrance in the loss of cations at the longer time frames as well. About 50% of weight loss was associated to Ca while 20% was to Al, leaving 6% to B where as the rest of the ions had shown almost insignificant contribution to the weight loss.

Dispersing co-crystals in a polymeric carrier may improve their physicochemical properties such as dissolution rate and solubility. Additionally co-crystal stability may be enhanced. However, such dispersions have been little investigated to date. This study focuses on the feasibility of dispersing co-crystals in a polymeric carrier and theoretical calculations to predict their stability. Acetone/chloroform, ethanol/water, and acetonitrile were used to load and grow co-crystals in a HPMCAS film. Caffeine-malonic acid and ibuprofennicotinamide co-crystals were prepared using solvent evaporation method. The interactions between each of the co-crystals components and their mixtures with the polymer were studied. A solvent evaporation approach was used to incorporate each compound, a mixture, and co-crystals into HPMCAS films. Differential scanning calorimetry data revealed a higher affinity of the polymer to acidic compounds than their basic counterparts as noticed by the depression of the glass transition temperature (Tg). Moreover, the same drug loading produced films with different Tgs when different solvents were used. Solubility parameter values (SP) of the solvents were employed to predict that effect on the depression of polymer Tg with relative success. SP values were more successful in predicting the preferential affinity of two acidic compounds to interact with the polymer. This was confirmed using binary mixtures of naproxen, flurbiprofen, malonic acid, and ibuprofen. On the other hand, dispersing basic compounds such as caffeine or nicotinamide with malonic acid in HPMCAS film revealed the growth of co-crystals. A dissolution study showed that the average release of caffeine from films containing caffeine-malonic acid was not significantly different to that of films containing similar caffeine concentration. The stability of the caffeine-malonic acid co-crystals in HPMC-AS was prolonged to 8 weeks at 95% relative humidity and 45°C. The theory developed in this project, that an acidic drug with a SP value closer to the polymer will dominate the interaction process and prevent the majority of the other material from interacting with the polymer, may have utility in designing co-crystal systems in polymeric vehicles

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2017-09-11T17:54:42Z No. of bitstreams: 2 Dissertação -Guilherme de Sousa Francisco - 2017.pdf: 2494658 bytes, checksum: 90f14f98ee056de8c44123948fa2113a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-09-18T12:01:51Z (GMT) No. of bitstreams: 2 Dissertação -Guilherme de Sousa Francisco - 2017.pdf: 2494658 bytes, checksum: 90f14f98ee056de8c44123948fa2113a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-09-18T12:01:51Z (GMT). No. of bitstreams: 2 Dissertação -Guilherme de Sousa Francisco - 2017.pdf: 2494658 bytes, checksum: 90f14f98ee056de8c44123948fa2113a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-07-14 / In recent decades, the search for materials with nonlinear optical (NLO) properties was intensified and currently covers a large variety of materials such as semiconductor multilayer structures, organic, inorganic and organometallic compounds. Non-linear optical materials have been of great interest in Physics and Chemistry of materials due to its potential applications in new technologies such as, electro-optical devices with optical keys, frequency converters and electro-optical modulators and photonic devices engineering. In this work we used Hartree Fock methods (HF) and Density Functional Theory (DFT), as implemented in the Gaussian09 package to obtain the geometric properties, electronics and optical from the compounds 4-nitroaniline, chalcone and malonic acid Salicyl-hydrazone ((HO_2 C)(C_6 H_3)(OH)NHNCH(COOH)_2). As the latter compound is not in literature, for the first time is presented a possible geometric structure, which the simulation shows a planar structure with asymmetry due to its “push-pull” character which are important characteristics for the second harmonic generation (SHG). Some properties were obtained, such as the dipole moment, polarizability and hyperpolarizabilities of the first compound order. Preliminary results show that the DFT produces larger values of hyperpolarizability by comparing with the results obtained by the Hartree Fock method. The hyperpolarizability is sensitive to the choice of the system of calculation, so in this work we used several arrangements of the basic functions as Pople Nernst, in addition to others found in the literature, in order to obtain the best possible description of the studied system. / Intensificou-se nas últimas décadas a busca por materiais com propriedades ópticas não lineares (ONL) e atualmente cobre uma grande variedade de materiais como estruturas semicondutoras multicamada, compostos orgânicos, inorgânicos e organometálicos. Materiais ópticos não lineares tem sido de grande interesse em Física e Química de materiais devido a potenciais aplicações em novas tecnologias como por exemplo, dispositivos eletro-ópticos com chaves ópticas, conversores de frequência e moduladores eletro-ópticos e engenharia de dispositivos fotônicos. Neste trabalho utilizou-se métodos Hartree Fock (HF) e Teoria Funcional da Densidade (DFT), como implementado no pacote Gaussian09, para obter as propriedades geométricas, eletrônicas e ópticas dos compostos 4-nitroanilina, chalcona e o Salicilhidrazona do ácido malônico ((HO_2 C)(C_6 H_3)(OH)NHNCH(COOH)_2). Como este último composto não se encontra na literatura, pela primeira vez é apresentado uma possível estrutura geométrica, onde a simulação mostra uma estrutura planar, possuindo assimetria devido o carater “push-pull”, que são características importantes para geração de segundo harmônico(SHG). Foram obtidas as propriedades, momento de dipolo, polarizabilidade e hiperpolarizabilidades de primeira ordem do composto. Os resultados preliminares mostram que a DFT produz valores maiores da hiperpolarizabilidade comparando com os resultados obtidos pelo método Hartree-Fock. A hiperpolarizabilidade é sensivel à escolha do regime de cálculo, por isso neste trabalho utilizou-se vários arranjos das funções de base tipo Pople Nernst, além de outras encontradas na literatura, afim de obter a melhor descrição possível do sistema estudado.

This dissertation has focused on the solid-state characterization of different co-crystal system as well as the effect of co-crystallization of these systems on pharmaceutical dosage form performance. Urea/ 2-MB, caffeine/ malonic acid, caffeine/ oxalic acid and theophylline/ malonic acid co-crystals were prepared using co-grinding- and co-precipitation techniques. In addition, the synthesis of co-crystals through two novel methods has been demonstrated. This includes compaction and convection mixing. The solid-state characterization of the co-crystals has been carried out using XRPD, Raman spectroscopy, DSC, TGA, hot-stage microscopy and SEM. After preparation of co-crystals, tablets have been produced from co-ground-, co-precipitated-, and physical mixtures using Compaction Studies Press (Kaleva), and the data were recorded to compare between the different mixtures, regarding compactibilty, compressibility and deformational properties. The DSC results showed that the physical mixtures of all systems, formed co-crystals during heating process. For systems of urea/ 2-MB, caffeine/ malonic acid and theophylline/ malonic acid, the co-ground mixture produced tablets with higher tensile strength compared with either co-precipitated or physical mixture. However, for caffeine/ oxalic acid system, the tensile strengths of compacts produced from the physical mixture were greater than those obtained from either co-ground or co-precipitated mixtures. The Heckel data suggested that urea/ 2-MB, caffeine/ malonic acid and theophylline/ malonic acid systems are Type 1 materials, as an extensive linearity during compression was indicative of a plastic deformation mechanism, while the caffeine/ oxalic acid system was Type 2 materials. However, the co-precipitated mixture of urea/ 2-MB system was the least compressible, as it possessed the greatest value of yield pressure (85 MPa) and the highest elastic recovery (7.42%). The co-precipitated mixture of both of caffeine/ malonic acid and theophylline/ malonic acid systems was the most compressible with small yield pressure values of (44 & 80 MPa) and elastic recovery of (7.2% & 6.56%), respectively. The co-ground mixture of caffeine/ oxalic acid possessed the highest value of yield pressure (166 MPa) and thus the lowest compressibility among other mixtures. Furthermore, the addition of microcrystalline cellulose and α-lactose monohydrate has affected the crystallinity as well as the tableting properties of the co-crystals. After the addition of excipients, the tensile strength of compacts was about 2 times higher than any other mixture. Finally, urea/ 2-MB and caffeine/ malonic acid co-crystals were successfully synthesized through convection mixing and compaction.

This dissertation has focused on the solid-state characterization of different co-crystal system as well as the effect of co-crystallization of these systems on pharmaceutical dosage form performance. Urea/ 2-MB, caffeine/ malonic acid, caffeine/ oxalic acid and theophylline/ malonic acid co-crystals were prepared using co-grinding- and co-precipitation techniques. In addition, the synthesis of co-crystals through two novel methods has been demonstrated. This includes compaction and convection mixing. The solid-state characterization of the co-crystals has been carried out using XRPD, Raman spectroscopy, DSC, TGA, hot-stage microscopy and SEM. After preparation of co-crystals, tablets have been produced from co-ground-, co-precipitated-, and physical mixtures using Compaction Studies Press (Kaleva), and the data were recorded to compare between the different mixtures, regarding compactibilty, compressibility and deformational properties. The DSC results showed that the physical mixtures of all systems, formed co-crystals during heating process. For systems of urea/ 2-MB, caffeine/ malonic acid and theophylline/ malonic acid, the co-ground mixture produced tablets with higher tensile strength compared with either co-precipitated or physical mixture. However, for caffeine/ oxalic acid system, the tensile strengths of compacts produced from the physical mixture were greater than those obtained from either co-ground or co-precipitated mixtures. The Heckel data suggested that urea/ 2-MB, caffeine/ malonic acid and theophylline/ malonic acid systems are Type 1 materials, as an extensive linearity during compression was indicative of a plastic deformation mechanism, while the caffeine/ oxalic acid system was Type 2 materials. However, the co-precipitated mixture of urea/ 2-MB system was the least compressible, as it possessed the greatest value of yield pressure (85 MPa) and the highest elastic recovery (7.42%). The co-precipitated mixture of both of caffeine/ malonic acid and theophylline/ malonic acid systems was the most compressible with small yield pressure values of (44 & 80 MPa) and elastic recovery of (7.2% & 6.56%), respectively. The co-ground mixture of caffeine/ oxalic acid possessed the highest value of yield pressure (166 MPa) and thus the lowest compressibility among other mixtures. Furthermore, the addition of microcrystalline cellulose and α-lactose monohydrate has affected the crystallinity as well as the tableting properties of the co-crystals. After the addition of excipients, the tensile strength of compacts was about 2 times higher than any other mixture. Finally, urea/ 2-MB and caffeine/ malonic acid co-crystals were successfully synthesized through convection mixing and compaction. / Islamic University of Omdurman and the Ministry of Higher Education in Sudan

No description available.