This dissertation describes the synthesis, structure and phase behavior of polyurethanes based on the mesogenic biphenol 4,4$\sp\prime$-bis(6-hydroxyhexoxy)biphenyl (BHHBP) and meta substituted tolylene/phenylene diisocyanates. The structure-property relationships were determined as a function of hydrogen-bonding, the position of the methyl group in the tolylene diisocyanate moiety (TDI) and the biphenol moiety. The liquid crystalline phase (mesophase) and crystalline phase were investigated primarily with differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and infrared spectroscopy. From this combination of characterization techniques, a more detailed description emerges about the thermodynamic stability and kinetic accessibility of each phase. Previous investigation of the (2,4-TDI/BHHBP) mesogenic polyurethane, 2,4-LCPU-6, has shown that this polymer is a monotropic liquid crystal. The influence of H-bonding on the structure and phase behavior of 2,4-LCPU-6 was determined by the synthesis of high molecular weight N-Methyl 2,4-LCPU-6, using a novel high temperature polymerization of a biscarbamoyl chloride with the BHHBP mesogenic diol. The comparison of the structure and physical properties of these two polymers revealed that H-bonding does not affect the mesophase morphology although its absence disrupts crystallinity and results in an enantiotropic liquid crystal. In addition, it was found that the effect of H-bonding on the mesophase-isotropic transition is enthalpic in nature. In contrast to the "regular" ($\alpha,\omega$-hexane diol) based polyurethanes (PUs), BHHBP derived polyurethanes (LCPUs) crystallize rapidly from their melts. This is due to the strong nucleating power of their thermodynamically unstable mesophases (monotropic L.C.) Hexafluoroisopropanol fast solvent-evaporation casting or rapid cooling from the melt resulted in thin films or bulk samples with a glassy mesophase morphology. During the subsequent heating scan, the mesophase to crystal transition takes place. Considerable amount of effort was expended to understand the nature of this transition. With the combination of vibrational spectroscopy which provides a measure of the localized structure, along with DSC and WAXS (which examine the long range order) we established the microstructural changes occurring in the different phases. Applying the results of previously mentioned analysis (kinetic control and phase perfection), highly oriented fibers were obtained for the mesogenic polyurethanes. Atomistic molecular simulations coupled with X-ray intensity refinement allowed us to determine the crystalline chain conformation and packing characteristics for the 2,6-LCPU-6 and 1,3-LCPU-6 (2,6-TDI and 1,3-Phenylene Diisocyanate (1,3-PDI) derived LCPUs). On the basis of structural similarity and well resolved WAXS powder patterns we extended the similar analysis to the "regular" polyurethanes as well (2,6-PU-6 and 1,3-PU-6). The good correlation between H-bonding distance and melting temperature for these four polymers suggests that melting is primarily controlled by the dissociation of H-bonds in the ordered domains.

The structure-property relationships in a new class of segmented copolymers, the smectic forming main chain liquid crystal polymers (LCPs), were systematically investigated. Soft segment length effects on polymer thermal phase behavior were studied. A series of segmented copolymers with different soft segment average lengths were prepared and characterized. Increasing soft segment length was found to favor the formation of smectic mesophases, irrespective of soft segment polydispersity. For interpreting the observations, a semi-quantitative thermodynamic theory was formulated, and a universal thermal phase diagram was proposed for segmented copolymers. Crystalline state structure and mesophase aggregation of these polymers were investigated. A crystalline state structure, in which the hard and soft segments are microphase separated, some of the soft segments have nearly fully extended conformation, and the hard segment crystal structure is independent of soft segment length, was proposed for smectic forming LCPs. The soft segment length was found to have significant effects on hard segment aggregation in the smectic phase. The observed thermal properties were interpreted. Morphology in the smectic state and melting behavior of a smectic forming LCP were studied. In the stable smectic state, the polymer showed a macrophase separated morphology, comprising smectic domains and an isotropic 'sea'. These smectic domains are cylindrical in shape and tens of microns in size. On cooling from smectic state, both smectic and isotropic phases crystallized and formed two different crystal structures. Consequently, the polymer showed dual melting endotherms, with their appearance strongly depending on sample thermal history. Crystallization kinetics of three different phases were investigated in a smectic forming LCP. The purely isotropic phase showed similar crystallization behavior as ordinary polymers. The crystallization of the purely smectic mesophase was found to be a local reorganization process and occurs within hard segment layers. The crystallization of the smectic-isotropic biphase showed complicated behavior, due to the simultaneous crystallization of both phases. The smectic phase was believed to nucleate the crystallization of the isotropic phase. Rheological behavior in the smectic state was investigated. A strong shear thinning at low shear rates was observed. On frequency sweeps, the polymer showed a two zone behavior, a 'solid-like' zone and 'liquid-like' zone. Further morphological investigations indicated that by low-rate shearing, the smectic domains were aligned along the shear direction. The domain alignment by flow was believed to be responsible for the observed rheological properties. By elongational flow, the polymer chains can also be oriented.

Diverse experimental techniques were used for the determination of acetaminophen (N-(p-Hydroxyphenyl)acetamide, N-acetyl-p-aminophenol) in aqueous and non-aqueous media. A study was performed on the electrochemical characterization of acetaminophen at a noble-metal electrode. A pretreatment procedure on the gold electrode was developed under basic conditions. The anodic peak current was the analytical parameter used. Spectrometric techniques were used as detection means, and their analytical potential was evaluated. Infrared techniques such as transmission and attenuated total internal reflection (ATR) were used for the quantitative determination of acetaminophen. The molar absorptivity of acetaminophen was calculated at the carbonyl infrared band from the calibration data obtained from the experiments performed in non-aqueous solvents using the transmission technique. The attenuated total internal reflection technique was used to overcome limitations on the use of the infrared transmission technique for aqueous based systems. A quantitative study was undertaken of the possibilities for the determination of acetaminophen in aqueous solutions by coupling flow injection analysis (FIA) with Fourier transform-infrared (FT-IR) spectrometry. Optimization of the basic flow injection FT-IR system was performed. The cylindrical internal reflection cell for liquid evaluation (CIRCLE$\sp\circler$) was used as the detector cell compatible with aqueous solutions. Applications to systems involving on-line chemical reactions by coupling the flow injection analysis technique with infrared spectrometric detection were described. Flow injection spectrophotometric and infrared detection methods were developed for the determination of acetaminophen based on its hydrolysis reaction with sodium hydroxide to form p-aminophenol and its oxidation with potassium ferricyanide to produce an orange-red species, p-benzoquinonemonoimine. The developed methods were evaluated by analysis of tablets of a commercial formulation. The ability of flow injection techniques for generating transient product profiles combined with the infrared mode for monitoring reaction species was investigated to help in the study of reaction mechanisms. Ab initio calculations were performed on acetaminophen at the 3-21G level of the theory. Structural parameters were optimized for the two conformations of acetaminophen. The calculated and experimental spectra were compared in terms of the infrared vibrational frequencies.

Os iodo-β-enaminoésteres cíclicos 13, 14, 15 e 16 (heterociclos nitrogenados de 5 membros) foram preparados pela iodociclização dos alquenil-β-enaminoésteres 7, 8, 9 e 10, respectivamente, com modificações na metodologia. Os tempos de reação foram diminuídos e o método de purificação foi modificado. Visando à extensão da metodologia para a obtenção de heterociclos nitrogenados de 6 membros, foi testada a iodociclização dos alquenil-S-enaminoésteres 11 e 12. O composto 11 forneceu o produto esperado 17 em 51% de rendimento enquanto que o composto 12 não sofreu ciclização nestas condições, porém ao modificá-las foi obtido composto 18\', via lactonização.As reações de desidroalogenação dos compostos 13, 14, 15 e 16 levaram aos produtos esperados 19, 20, 21 e 22, com rendimentos de 93, 99, 75 e 93%, respectivamente. O composto 17 não gerou nenhum produto nestas condições, mas ao modificá-las obteve-se o composto 23\', resultante de substituição nucleofilica interna, com 79% de rendimento. Nestas condições, os compostos 15 e 16 sofreram eliminação de HI gerando os compostos 21\' e 22\', respectivamente. / Cyclic iodo-β-enaminoesthers 13, 14, 15 e 16 (five-membered nitrogen heterocycles) were prepared by iodocyc1ization of alkenyl-β-enaminoesthers 7, 8, 9 e 10, respectively, with modifications in the method. The reaction times were diminished and the method of purification was changed. In order to extend this metodology to obtain six-membered nitrogen heterocycles, the iodocyclization of the alkenyl-β enaminoesthers 11 and 12 was tested. Compound 11 furnished the expected product 17 in 51% yield while compound 12 did not undergo cyclization in such conditions, however by changing them compound 18\' was obtained, via lactonization. The dehalogenation reaction of compounds 13, 14, 15 and 16 afforded the expected products 19, 20, 21 and 22, in 93, 99, 75 and 93% yield, respectively. Compound 17 did not furnish any products in these conditions, but modifying them compoud 23\' was obtained, resulting from a internal nucleophilic substitution, in 79% yield. In these conditions, compounds 15 and 16 underwent HI elimination giving compounds 21\' e 22\', respectively.

Os iodo-β-enaminoésteres cíclicos 13, 14, 15 e 16 (heterociclos nitrogenados de 5 membros) foram preparados pela iodociclização dos alquenil-β-enaminoésteres 7, 8, 9 e 10, respectivamente, com modificações na metodologia. Os tempos de reação foram diminuídos e o método de purificação foi modificado. Visando à extensão da metodologia para a obtenção de heterociclos nitrogenados de 6 membros, foi testada a iodociclização dos alquenil-S-enaminoésteres 11 e 12. O composto 11 forneceu o produto esperado 17 em 51% de rendimento enquanto que o composto 12 não sofreu ciclização nestas condições, porém ao modificá-las foi obtido composto 18\', via lactonização.As reações de desidroalogenação dos compostos 13, 14, 15 e 16 levaram aos produtos esperados 19, 20, 21 e 22, com rendimentos de 93, 99, 75 e 93%, respectivamente. O composto 17 não gerou nenhum produto nestas condições, mas ao modificá-las obteve-se o composto 23\', resultante de substituição nucleofilica interna, com 79% de rendimento. Nestas condições, os compostos 15 e 16 sofreram eliminação de HI gerando os compostos 21\' e 22\', respectivamente. / Cyclic iodo-β-enaminoesthers 13, 14, 15 e 16 (five-membered nitrogen heterocycles) were prepared by iodocyc1ization of alkenyl-β-enaminoesthers 7, 8, 9 e 10, respectively, with modifications in the method. The reaction times were diminished and the method of purification was changed. In order to extend this metodology to obtain six-membered nitrogen heterocycles, the iodocyclization of the alkenyl-β enaminoesthers 11 and 12 was tested. Compound 11 furnished the expected product 17 in 51% yield while compound 12 did not undergo cyclization in such conditions, however by changing them compound 18\' was obtained, via lactonization. The dehalogenation reaction of compounds 13, 14, 15 and 16 afforded the expected products 19, 20, 21 and 22, in 93, 99, 75 and 93% yield, respectively. Compound 17 did not furnish any products in these conditions, but modifying them compoud 23\' was obtained, resulting from a internal nucleophilic substitution, in 79% yield. In these conditions, compounds 15 and 16 underwent HI elimination giving compounds 21\' e 22\', respectively.

In much of the literature about organic photovoltaics, the topic is framed within the current landscape of energy production and the research on these materials is cited as a possible solution to the energy crisis looming ahead. Despite being the most frequent, this is by no means the only perspective that can be offered. Indeed, the same research may also be set within the larger perspective offered by the field of functional materials. These materials are usually exploited for their particular responses to electrical, magnetic and chemical stimuli and are at the basis of many technologies fundamental to our society. The prominent position of functional materials in modern science is due to the emergence of novel technological needs that such materials have been able to satisfy thanks to their peculiar properties. These properties have been rationalised and mastered by expanding the theoretical description of the underlying physical mechanisms. This theoretical body, combined with the growth and diffusion of computational capabilities has fostered a change in the scientific paradigm underpinning the research effort. More and more, the predictive power of numerical approaches is exploited to lead the way in the exploration of the immense chemical space. The ultimate promise is to achieve the purpose-driven design of compounds thanks to which the molecular structure can be engineered before the actual synthesis to meet the demands dictated by a specific application. To fulfil this role, computational approaches need to be able to simulate the solid state properties at the most relevant time and length scales. If this can be accomplished then a reliable prediction of the performance can be achieved. The current work deals with the development and application of one such protocol, for the particular case of organic photovoltaic semiconductors. Given the specific application, the properties targeted are light absorption and charge transport. Particular effort is put in the simulation of local morphologies at scales above the molecular one to describe supramolecular organisation with sufficient resolution. In this thesis, the protocol is applied to two molecular systems employed in solar devices. Both systems have been selected on the basis of data suggesting that a detailed microscopic description of their behaviour could be highly informative about the aspects responsible for their photovoltaic performance. In particular, chapter 3 details the investigation of a small-molecule donor that has been shown in the literature to have a remarkable behaviour in absorption. While chapter 4 reports the study of a donor-acceptor dyad used as active layer in single-component solar devices with relatively high conversion efficiency. In both cases, the computational protocol has proven capable of providing a detailed microscopic description of the systems. The picture drawn has allowed to clarify the plausible mechanisms behind the observations and to rationalise these behaviours in a broader and more general theoretical framework.

Uma das propriedades fundamentais de soluções de micelas aquosas é sua capacidade de solubililizar uma ampla faixa de solutos orgânicos com diferentes graus de polaridade e hidrofobicidade. Recentemente Quina et. aI., estudaram as interações químicas específicas que governam a solubilidade para um ampla faixa de solutos orgânicos em micelas usando relações lineares de energia livre de solvatação (LSERs), baseado nos parâmetros empíricos do soluto desenvolvido por Abraham. O presente trabalho trata a solubilização de solutos orgânicos em micelas baseado em parâmetros obtidos unicamente da estrutura molecular do soluto através de cálculos de química quântica. Nossos resultados mostram que valores experimentais de Ks para solubilização de solutos orgânicos em detergentes aniônicos (micelas de SDS, dodecil sulfato de sódio e agregados de SDS com PEG-polietilenoglicol) podem ser reproduzidos usando parâmetros teóricos. A relação linear teórica de energia livre de solvatação resultante é quimicamente condizente com LSERs baseados em parâmetros empíricos do soluto. No caso de detergentes catiônicos e não iônicos, a metodologia apresenta limitações, por que o método de cálculo de cargas formais usando a definição de análise populacional de Mulliken não descreve de maneira apropriada o caráter ácido e básico das pontes de hidrogênio entre os solutos e a água. Alternativas para resolver o problema da limitação imposta pelos parâmetros teóricos, mantendo a aproximação linear de energia livre, são discutidas. / One of the most fundamental properties of aqueous micelar solutions is their ability to solubilize a wide variety of organic solutes with quite distinct polarities and degree of hydrophobicity. Recently Quina et al., studied the specific chemical interactions governing the solubilities of a wide range of solutes in micelles using linear solvation energy relationships (LSERs) based on empirical solute parameters developed by Abraham. This work reports an investigation of the solubilization of organic solutes in micelles based on the use of theoretical solute parameters derived from quantum chemical calculations Our results show that the experimental Ks values for solubilization of organic solutes in anionic detergents (micelles of SDS-sodium dodecyl sulfate and aggregate formed between SDS and PEG-poly(ethylene glycol)) can be reproduced using theoretical parameters. The resultant theoretical linear solvation energy relationships are chemically consistent with LSERs based on empirical solute parameters. In the case of cationic and nonionic detergents, the theoretical parameters used to describe hydrogen bonding fail because methods of calculating formal charges using the concept of Mulliken populational analysis cannot describe hydrogen bonding donor and acceptor character in an appropriate way. Possible strategies to solve the theoretical descriptor problem in the context of the linear free energy approximation are discussed.

Uma das propriedades fundamentais de soluções de micelas aquosas é sua capacidade de solubililizar uma ampla faixa de solutos orgânicos com diferentes graus de polaridade e hidrofobicidade. Recentemente Quina et. aI., estudaram as interações químicas específicas que governam a solubilidade para um ampla faixa de solutos orgânicos em micelas usando relações lineares de energia livre de solvatação (LSERs), baseado nos parâmetros empíricos do soluto desenvolvido por Abraham. O presente trabalho trata a solubilização de solutos orgânicos em micelas baseado em parâmetros obtidos unicamente da estrutura molecular do soluto através de cálculos de química quântica. Nossos resultados mostram que valores experimentais de Ks para solubilização de solutos orgânicos em detergentes aniônicos (micelas de SDS, dodecil sulfato de sódio e agregados de SDS com PEG-polietilenoglicol) podem ser reproduzidos usando parâmetros teóricos. A relação linear teórica de energia livre de solvatação resultante é quimicamente condizente com LSERs baseados em parâmetros empíricos do soluto. No caso de detergentes catiônicos e não iônicos, a metodologia apresenta limitações, por que o método de cálculo de cargas formais usando a definição de análise populacional de Mulliken não descreve de maneira apropriada o caráter ácido e básico das pontes de hidrogênio entre os solutos e a água. Alternativas para resolver o problema da limitação imposta pelos parâmetros teóricos, mantendo a aproximação linear de energia livre, são discutidas. / One of the most fundamental properties of aqueous micelar solutions is their ability to solubilize a wide variety of organic solutes with quite distinct polarities and degree of hydrophobicity. Recently Quina et al., studied the specific chemical interactions governing the solubilities of a wide range of solutes in micelles using linear solvation energy relationships (LSERs) based on empirical solute parameters developed by Abraham. This work reports an investigation of the solubilization of organic solutes in micelles based on the use of theoretical solute parameters derived from quantum chemical calculations Our results show that the experimental Ks values for solubilization of organic solutes in anionic detergents (micelles of SDS-sodium dodecyl sulfate and aggregate formed between SDS and PEG-poly(ethylene glycol)) can be reproduced using theoretical parameters. The resultant theoretical linear solvation energy relationships are chemically consistent with LSERs based on empirical solute parameters. In the case of cationic and nonionic detergents, the theoretical parameters used to describe hydrogen bonding fail because methods of calculating formal charges using the concept of Mulliken populational analysis cannot describe hydrogen bonding donor and acceptor character in an appropriate way. Possible strategies to solve the theoretical descriptor problem in the context of the linear free energy approximation are discussed.

Neutral cyclometalated platinum(II) N-heterocyclic carbene complexes [Pt(C^C*)(O^O)] with C^C* ligands based on 1-phenyl-1,2,4-triazol-5-ylidene and 4-phenyl-1,2,4-triazol-5-ylidene, as well as acetylacetonato (O^O = acac) and 1,3-bis(2,4,6-trimethylphenyl)propan-1,3-dionato (O^O = mesacac) ancillary ligands were synthesized and characterized. All complexes are emissive at room temperature in a poly(methyl methacrylate) (PMMA) matrix with emission maxima in the blue region of the spectrum. High quantum efficiencies and short decay times were observed for all complexes with mesacac ancillary ligands. The sterically demanding mesityl groups of the mesacac ligand effectively prevent molecular stacking. The emission behavior of these emitters is in general independent of the position of the nitrogen in the backbone of the N-heterocyclic carbene (NHC) unit and a variety of substituents in 4-position of the phenyl unit, meta to the cyclometalating bond.