This thesis examines the electro-optic, electric and electrochemical properties of liquid crystal (LC) materials in self-assembly systems, that is, liquid crystal-polymer electrolyte composites (LC-PEs), LC binary mixtures, and their potential application in dye-sensitised solar cells (DSSCs). The birefringence of LCs causes light modulation, which can be controlled by an applied voltage and electric field. In particular, the LCs are used as one of the components for the electrolyte redox couple which is responsible for charge transfer mechanism in DSSCs. In this work, LC-PEs were developed by dissolving LCs in polymer electrolytes; using a homologous series of cyanobiphenyls in a range of concentrations, alkyl chain lengths and dielectric permittivities. We found that doping the polymer electrolyte with 15% 4'-cyano-4'-pentylbiphenyl (5CB) improved ionic conductivity by up to 13 % compared to pure polymer electrolyte. Materials with positive dielectric permittivity and shorter alkyl chain length have been identified to be compatible with iodide/triiodide (I^-/I_3^-)-based polymer electrolytes. In DSSCs, 15% 5CB and 15% E7 LC-PEs exhibited the best efficiencies of 3.6 % and 4.0 %, respectively. In addition to LC-PEs, the self-assembly properties of smectic phase LCs were also utilised as templates for controlling the polymer structure in polymer electrolytes. A porous polymer network was prepared using various techniques including self-assembly, by applying an electric field and using a polyimide (PI) alignment layer. We found that the electrochemical and photovoltaic properties of these materials strongly correlated to the morphology/structure with the self-assembled structure, thus showing the best photovoltaic performance (5.9 %) even when compared with a reference solar cell (4.97 %). Finally, this thesis explores the interaction of LCs with graphene (Gr) in DSSC device architectures. Gr-based DSSCs were fabricated using different processing conditions, with the result being that Gr improved the performance of the DSSCs. The highest efficiency obtained was 5.48 % compared to the 4.86 % of a reference DSSC. The incorporation of LC-PEs in Gr-based DSSCs improved the performance of DSSCs was observed in devices with low concentrations of LCs due to the Gr inducing planar alignment of LCs. These results suggest a new strategy to improve DSSC efficiency by incorporating LC materials in the polymer electrolyte component. Even though these LCs are highly insulating, their self-assembly and dielectric polarisability help enhance ionic conductivity and optical scattering when doped into polymer electrolytes. This work can be extended in a fundamental way to elucidate the ionic conduction mechanism of LC-based electrolyte systems. Furthermore, it would be interesting if the benefits of using LC-PEs and smectic-templated polymer electrolytes (Sm-Pes) can be translated further in commercial electrochemical energy conversion systems.

Results are presented from a series of simulations undertaken to determine the effect of a novel form of molecular biaxiality upon the phase behaviour of the well established Gay-Berne (GB) liquid crystal model. Firstly, the simulation of a bulk system interacting via the Internally-Rotated Gay-Berne (IRGB) potential, which offers a single-site representation of a molecule rigidly constrained into a zig-zag conformation, is presented. The results of simulations performed for systems of IRGB particles with an aspect ratio of 3:1 confirm that the introduction of biaxiality into the model results in the destabilisation of the orientationally ordered phases. For particles with a sufficiently pronounced zig-zag conformation, this results in the complete destabilisation of the smectic A phase and the smectic B phase being replaced by the tilted smectic J phase. Following these observations, the effect upon the phase behaviour of increasing molecular elongation is also considered, with an increase in the aspect ratio from 3:1 to 4:1 resulting in the nematic and smectic J phases being replaced by smectic A and smectic G phases respectively. Secondly, a version of the IRGB potential modified to include a degree of molecular flexibility is considered. Results obtained from bulk systems interacting via the flexible IRGB for 3:1 and 4:1 molecules show that the introduction of flexibility results in the destabilisation of the smectic A phase and the stabilisation of the nematic and tilted hexatic phases. Finally, the effect upon the phase behaviour of the rigid IRGB model of the inclusion of a longitudinal linear quadrupole is examined. These results show that increasing quadrupole moment results in the destabilisation of the tilted hexatic phase, although the biaxial order parameter is increased with increasing quadrupole moment. There is no clear correlation between quadrupole magnitude and the other observed phase transitions, with the nematic and smectic A phases being variously stabilised and destabilised with increasing quadrupole magnitude. For the 4:1 molecules with large quadrupole moments, buckled smectic layers are observed where some molecules are tilted with respect to a local layer normal. Of all the systems considered here, this buckled structure is the one which most closely resembles the elusive smectic C phase.

Thermal and viscous forces compete for dominance at the microscopic length-scales which govern the behaviour of many soft or biological systems. We study three systems of increasing complexity with the central goal of understanding the statistical or hydrodynamic nature of their mechanics. First we study experiments that have been conducted on ferromagnetic colloidal rods. At equilibrium, the magnetically pinned rod is observed to randomly flip between two orientational states, which our theoretical analysis shows is due to a competition between entropic and Hamiltonian forces. We show analytically how entropic forces can arise by considering the coupling between observed and unobserved variables of a system. Experiments in which a rod is driven out of equilibrium by a rotating field display three phases of steady-state behaviour as a function of driving frequency. Using Brownian dynamics simulations we match the lower critical frequency to the experimentally obtained values, showing that thermal fluctuations play an important role in this regime and propose a simple argument to demonstrate that hydrodynamic interactions between the substrate and rod affect the upper critical frequency. We then turn to the biophysical topic of cell locomotion in viscoelastic media. In order to study how bacterial flagella interact with similarly-sized polymers in their environment, we construct a Stokesian dynamics model of a helical filament and bead--spring polymer. Simulating their interaction first for a pinned--rotating helix, then for a swimming helix, we demonstrate that large polymers become hydrodynamically entrained by the flagellum and coil around it, causing both pinned and swimming flagella to expend more work. For the swimming helix, this results in a reduction of swimming speed on average. Finally, we consider an active nematic fluid confined to a channel and show that the inclusion of a passive colloid induces a global state of coherent flow maintained by the intrinsic activity of the system. This flow is persistent, and transports the colloid with it along the channel. By this mechanism, a passive colloid is able to spontaneously induce its own transport through an otherwise quiescent fluid.

Made available in DSpace on 2014-06-11T19:25:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-15Bitstream added on 2014-06-13T20:13:47Z : No. of bitstreams: 1 rissi_nc_me_arafcf.pdf: 1922586 bytes, checksum: 97623f411e93060072eac4e313c8665c (MD5) / Nas últimas décadas, têm se observado um interesse crescente na inovação de sistemas nanoestruturados utilizados para a liberação prolongada de diversas substâncias. No caso de fármacos, as formulações de liberação prolongada apresentam diversas vantagens em relação às formas convencionais de administração, tais como alta eficiência de liberação, controle preciso da dosagem por períodos prolongados e diminuição da toxicidade. Dependendo da composição, uma mistura entre tensoativo, óleo e água podem formar diversos sistemas nanoestruturados com os mais variados níveis de organização estrutural, característica que interferi diretamente no processo de liberação. Neste trabalho esses sistemas foram obtidos pela construção de diagramas de fases, utilizando tensoativos com diferentes graus de hidrofilia, o PPG-5-Ceteth-20 e o Oleth 10, como fases oleosas o Ácido Oleico e o Miristato de Isopropila. Através dos diagramas foi possível observar diferenças significativas relacionadas com as características dos sistemas, devido à capacidade que o Oleth 10 como tensoativo e o Ácido Oleico como fase oleosa têm em diminuir a tensão interfacial, facilitando a formação de uma extensa região de sistemas transparentes. A caracterização da estrutura interna dos mesmos foi feita por microscopia de luz polarizada, espalhamento de raios-X a baixo ângulo (SAXS) e medidas reológicas. Através da microscopia foi possível identificar características isotrópicas e anisotrópicas, sendo posteriormente confirmadas pelo SAXS, o qual permitiu não só a identificação das nanoestruturas, mas também uma avaliação mais aprofundada sobre o nível de organização estrutural, principalmente dos arranjos líquido-cristalinos, característica que foi reforçada através das medidas reológicas, as quais proporcionaram uma... / In the last decades it has been observed a growing interest in nanostructure systems innovations, wich are response for control release of several substances. In the case of drugs, the formulations which promote the controlled release present many advantages against the conventional forms of administration, such as high release efficiency, precise dosage control for long periods and toxicity decreasing. Depending on the composition, a surfactants mixture, oil and water can form different nanostructured systems with the most different organization structure degrees, which can directly interfere in the global process of drugs release. In this paper the nanostructured systems were obtained through the building of phases diagrams, using surfactants with different hydrophilic degrees, the PPG-5-Ceteth-20 and the Oleth 10, as oil phases the Oleic Acid and Isopropil Miristate. It was possible to observe significant difference between the diagrams wich are related with the characteristics of the obtained systems, due to a higher capacity that Oleth 10 as a surfactant and the Oleic Acid as oil phase have in decreasing the interfacial tension, and consequently promoting a greater region of transparent systems. The internal structure of these systems was characterized by polarized light microscopy, small angle X-ray scattering (SAXS) and rheological measurements. Through the microscopy it was possible to identify the isotropic and anisotropic characteristics, being later confirmed by SAXS. This characterization through SAXS allowed not only the nanostructures identification, but also a more deeply evaluation on the structure degree, mainly on the arrangement of liquid-crystalline. The rheological test also provided a better understanding about the degree of internal structure of nanostructured systems, mainly those... (Complete abstract click electronic access below)

Na presente tese, são apresentados estudos de microscopia óptica e RMN em mesofases liotrópicas colestéricas, obtidas a partir da inclusão de novos indutores (L - SORBOSE, diacetona - L - sorbose, DAS, e diacetona - 2 - ceto - L - gulonato de potássio, DGK) em sistemas nemáticos do tipo II ou N-D , baseados em diversos anfifílicos. Utilizando técnicas de microscopia óptica sob luz polarizada, constatou-se a distorção do arranjo helicoidal devido à competição entre a orientação por parede e o poder de torção dos indutores. Para determinar o sentido de torção (helicidade) da mesofase foram adaptados métodos aplicados a termotrópicos. Verificou-se que a configuração absoluta do indutor deve ter um papel importante apenas quando este se aloja predominantemente na porção aquosa. Indutores hidrofóbicos apresentam sempre a mesma helicidade (sentido de torção) em diferentes sistemas, uma vez que o ambiente parafínico intra-micelar é essencialmente o mesmo. Por outro lado, indutores hidrofílicos ou hidrofóbicos capazes de fortes interações com a d.c.e. originam mesofases cuja helicidade pode ser alterada por mudanças na distribuição de cargas na superfície micelar. Através da inclusão de laurato de potássio e cloreto de decilamônio perdeuterados em suas respectivas mesofases, obteve-se, por meio da RMN de deutério a 15,3 MHz, os perfís de ordem para os sistemas colestéricos baseados nos tres indutores citados. Os resultados permitem apontar que a sorbose se aloja predominantemente na porção aquosa e o DGK na porção hidrocarbônica. O DAS se aloja dentro da micela em mesofases de laurato de potássio e fora em mesofases de cloreto de decilamônio. Ainda com o emprego da RMN, foi possível seguir o comportamento dos indutores DAS e DGK em diferentes mesofases através da substituição da acetona ligada às posições 4,6 por acetona perdeuterada. No caso do DGK, observaram-se dubletes distintos para os dois metilas em todas as mesofases. O DAS teve comportamento análogo, exceto em mesofases baseadas em decilsulfato de sódio, onde os metilas apresentaram equivalência. Neste caso, verificou-se a alteração da colestericidade do sistema quando o íon sódio é substituido por césio. O ordenamento desta espécie pôde ser acompanhado pelo desdobramento quadrupolar através da RMN de césio - 133 a 13,1 MHz. Analisando as relações entre os desdobramentos quadrupolares dos dois grupos metilas deuterados, no DAS e no DGK, pode-se constatar que o ancoramento destas espécies é diferente nos diversos sistemas investigados. Estas relações correspondem, também, a uma avaliação do poder de torção destes indutores. / In the present thesis, studies on optical microscopy and NMR in cholesteric lyotropic mesophases are reported. These phases were obtained through the addition of new cholesteric inducers (L - SORBOSE, diacetone - L - sorbose, DAS, and potassium diacetone - 2 - keto - L - gulonate, DGK) to nematic type II or N-D systems. By using polarizing microscopy it was observed a distortion of the helical array due to a competition involving orientational wall effects and the inducers twisting power. Methods used for thermotropic cholesteric twisting sense (helicity) determination were adapted for lyotropic systems. The inducer absolute configuration plays an important role only when it remains predominantly in the aqueous portion. Hydrophobic inducers added to different systems, lead to the same helicity, since the paraffinic intra-micellar environment is essentialy the same. By the other hand, hydrophylic or hydrophobic inducers subjected to strong interactions with the e.d.l., will originate cholesteric mesophases whose helicity can be rnodified by changes on the charge distribution of the micellar surface. By including perdeuterated potassium laurate and decylammoniurn chloride in their respective mesophases, it was posible to obtain, by deuterium NMR technics, at 15.3 MHz, order profiles of cholesteric systems including these new inducers. The results point out that SORBOSE remains predominantly at the aqueous portion and DGK on the hydrocarbonic cornpartment. The DAS molecule remains inside the micelle, in potassium laurate mesophases, and outside the micelle, in decylammonium chloride systems. Using deuterium NMR, it was possible to follow the behaviour of DAS and DGK inducers, by substitution of the acetone bonded to 4,6 position for perdeuterated acetone. In the case of DGK, distinct doublets were assigned for each methyl group in all mesophases. For DAS case, the same behaviour was observed, except for sodium decylsulphate mesophases, where both methyl groups were equivalent. For this inducer a change of cholesteric properties were observed when the sodium ion was exchanged for cesium ion. The order in these systems was additionally followed by 133-cesium NMR at 13.1 MHz. By analising the relationship between the quadrupolar splittings of the deuterated methyl groups, in DAS and DGK, it was verified that there are changes in the inducer anchoring for different mesophases. These relationships correspond, also, to an evaluation of the inducer twisting power.

Made available in DSpace on 2014-06-11T19:24:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-08-07Bitstream added on 2014-06-13T20:31:11Z : No. of bitstreams: 1 longo_dp_me_arafcf.pdf: 1190234 bytes, checksum: b0c008283bedbe34e959757962ddfb37 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A mistura de óleo, água e tensoativo é capaz de formar estruturas e sistemas variados, dependendo das características e da proporção dos componentes utilizados. Sistemas microestruturados, como cristais líquidos e microemulsões, são utilizados para encapsular fármacos e substâncias ativas em produtos farmacêuticos e cosméticos. O objetivo desse trabalho foi desenvolver sistemas microestruturados para a incorporação da cafeína com finalidade de uso tópico para otimizar o tratamento da hidrolipodistrofia ginóide. A mistura direta de PPG-5-Ceteth-20 (tensoativo), adipato de dibutila (fase oleosa) e água em diferentes proporções possibilitou a obtenção de formulações com formas de estruturação variadas, como microemulsão, emulsão e mesofases líquido-cristalinas. As formulações obtidas foram caracterizadas por meio de microscopia de luz polarizada, determinação de índice de refração, densidade relativa e condutividade e comportamento reológico. Estudos de solubilidade mostraram que os sistemas foram capazes de solubilizar cerca de 1,5% de cafeína. Estudos de liberação in vitro, que utilizaram modelo de célula de difusão em sistema estático do tipo Franz adaptada ao equipamento de dissolução indicaram que as formulações apresentaram características de sistemas reservatórios de liberação prolongada. Para o estudo de permeação in vivo foram utilizados suínos machos, Landrace x Large White, submetidos ao tratamento com formulação acrescida ou não de cafeína. Fragmentos de pele e hipoderme foram retirados para a análise histológica. A formulação com características de cristal líquido de fase hexagonal foi eficaz em aumentar a permeação cutânea à cafeína, facilitando assim sua ação. A cafeína aplicada desta forma fez com que houvesse uma redução significativa da espessura da hipoderme. O sistema atua como promotor de permeação e garante a eficácia da cafeína no tratamento da celulite. / Oil, water and surfactant mixture may form a variety of structures and phases accordingly to the characteristics and the ratio of the used components. Microcompartmented systems as liquid crystals and microemulsions are used to encapsulated drugs and active substances in pharmaceutical and cosmetic products. The objective of this research was the development of microcompartmented systems for incorporation of caffeine with the purpose of topical use on treatment of the gynoid lipodystrophy. The direct mixture of PPG-5-Ceteth-20 (surfactant), dybutyl adipate (oil phase) and water in differents proportions made possible to obtain formulations with different structuring forms as microemulsions, emulsions and liquid crystalline mesophases. The formulations were characterized through the polarization light microscopy, refractive index, relative density, conductivity and behavior rheological. Solubility studies were accomplished showed that the systems were capable to solubilize about 1,5% of caffeine. In vitro release studies using the cell of diffusion model in static system of Franz's type adapted to the dissolution equipment indicated formulations with characteristics of reservoirs systems. The permeability study in vivo used male pig (Landrace x Large White) and they were submitted to the treatment. Formulations with or without caffeine were applied. Skin's fragments and hypoderm of them were removed for histology analysis after the treatment. The formulation with liquid crystal of hexagonal phase characteristics was efficient in increasing skin permeability to the caffeine, thus facilitating its drug action. The application of caffeine this way led to a significant reduction of the hypoderms thickness. The developed system is adjusted for topical use, is skin penetration enhancers and it guarantees the effectiveness of the caffeine in the treatment of the cellulite.

Submitted by Maike Costa (maiksebas@gmail.com) on 2016-05-20T14:36:07Z No. of bitstreams: 1 arquivo total.pdf: 6564375 bytes, checksum: cc7202d5f55c0bd22656d7a99ef5e9df (MD5) / Made available in DSpace on 2016-05-20T14:36:08Z (GMT). No. of bitstreams: 1 arquivo total.pdf: 6564375 bytes, checksum: cc7202d5f55c0bd22656d7a99ef5e9df (MD5) Previous issue date: 2015-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Liquid crystals (LCs) are functional soft materials of dynamic nature with shape and anisotropic properties. Control of the intrinsic self-assembly and self-organization properties in LCs may be accomplished by incorporating an optical switch within the mesogenic structure, such as a photoresponsive azo group. In this context, this dissertation shows the synthesis and characterization of the mesomorphic and optical properties of compounds derived from 1,4-disubstituted azobenzenes. The molecules are designed in order to contain an azobenzene rod-shaped rigid core. At one end, the molecules hold substituents with different sizes, polarity, and electronic properties (NO2, Cl or OR groups). At the other end of the molecules are connected, via an eter bond, to chains of 6 or 11 carbons possessing a terminal polar hydrophilic group, such as hydroxyl or imidazolium salt. In another series of molecules, the peripheral region is built on anhydrophobic portion. They contain an high dipole moment carbonyl group of aliphatic and aromatic ester with or without mesogenic extension. The chemical structures of final compounds were characterized by spectrometric methods (IR,1H and 13C NMR). The mesomorphic properties were investigated by Polarizing Optical Microscopy and Differential Scanning Calorimetry. Among the eighteen molecules synthesized, seven are LCs. Our studies reveal an interesting relation between the stereoeletronic nature of terminal groups and the observed LC phase. The hydroxyl group generated nematic phase, while compounds with ester carbonyl show a lamellar polymorphism with SmA and SmC phases, indicating the carbonyl increase the stability of liquid crystalline phases. The compounds containing terminal imidazolium salts show only SmA phase with an interesting characteristic of keeping the phase up to room temperature. Preliminar studies of the azo group photoisomerization indicate that the phase may be broken by expose to UV light. Thus, this molecular system may have potential technological applications in the photocontrol of liquid crystalline phase and enhanced functions in optoelectronic devices. / Cristais líquidos (CLs) constituem materiais moles funcionais de natureza dinâmica com forma e propriedades anisotrópicas. O controle das propriedades intrínsecas de automontagem e auto-organização de CLs pode ser efetuado pela incorporação de um interruptor ótico, tal como um grupo espaçador azo fotorresponsivo. Neste contexto, esta dissertação apresenta a síntese e caracterização das propriedades mesomórficas e óticas de seis séries de compostos derivados do azobenzeno 1,4-dissubstituídos. As moléculas são constituídas pelo núcleo rígido central azobenzeno, e nas extremidades estão dispostos substituintes com diferentes tamanhos, polaridade e propriedades eletrônicas, como grupos NO2, Cl e OR. Na outra extremidade, conectados por uma ligação éter estão cadeias com 6 ou 11 carbonos, e na porção final grupos hidrofílicos polares, tais como hidroxila e sais de imidazólio, e também grupos com elevado momento dipolar lateral, como carbonila de ésteres de diferentes grupos (alifáticos e aromáticos). Os compostos foram caracterizados por espectroscopia na região do Infravermelho, Ressonância Magnética Nuclear de 1H e 13C. As propriedades mesomórficas foram investigadas por Microscopia Ótica de Luz Polarizada e Calorimetria Diferencial de Varredura. Entre as dezoito moléculas sintetizadas, sete foram CLs. Foi descoberta uma relação interessante entre a natureza estereoeletrônica dos grupos terminais e as fases exibidas. O grupo hidroxila terminal levou a geração de fase nemática, enquanto que os compostos com carbonila de ésteres exibiram um polimorfismo lamelar mais ordenado com fases SmC e SmA, indicando que as carbonilas aumentam a estabilidade das fases líquido cristalinas. Os compostos contendo sais de imidazólio terminal mostraram apenas SmA, com uma interessante manutenção da fase até a temperatura ambiente durante o resfriamento. Resultados obtidos no estudo da fotoisomerização do grupo azo destes compostos comprovaram a potencialidade de tais sistemas moleculares em aplicações tecnológicas como fotocontroladores da fase LC e de suas propriedades funcionais em dispositivos. Palavras-chave: Cristais líquidos, azobenzenos, fotoisomerização.

Submitted by ANA KARLA PEREIRA RODRIGUES (anakarla_@hotmail.com) on 2017-07-28T12:53:24Z No. of bitstreams: 2 arquivototal.pdf: 4165677 bytes, checksum: cd4f0d6e638890dadcf1bb5f730949a1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-07-28T12:53:24Z (GMT). No. of bitstreams: 2 arquivototal.pdf: 4165677 bytes, checksum: cd4f0d6e638890dadcf1bb5f730949a1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The low molecular weight materials with -conjugated system are widely studied by the academic community and the industry. The properties shown by such systems collaborate are the basis for electro-optical devices such as OLEDs, OFETs and solar cells (organic semiconductors). Liquid crystals compose an important group of low molecular weight materials due to their properties: the order of solid and flow of liquid. In this context, this work presents the synthesis and characterization of the thermal and optical properties of three groups of conjugated compounds derived from benzylidene ketones. The structures of these compound were designed in order to get rod-like structures to form calamitic liquid crystals. The molecules of this work are based on the structure of benzylideneketone 3-methoxy-4-substituted with alkoxyl chains of 4, 10 and 12 carbons. Cyclic and acyclic ketones separate the aromatic rings. The target molecules were characterized by spectrometric methods (IR, 1H and 13C NMR). The thermal properties were investigated by POM, DSC and TGA. One of nine molecules showed mesomorfic phase, three of them did not crystalize on cooling to the room temperature, and the other ones did not show any type of liquid crystalline phase. The thermal decomposition varied from 215 °C to 345 °C. The optical studies were performed in solution by UV spectroscopy. The target compounds exhibited a strong absorption band varying from 330 nm to 370 nm ( = 104 L.mol-1.cm-1) attributed to the -* electronic transitions. / Os materiais de baixa massa molecular com elevada conjugação  são interessantes alvos de pesquisa na academia e na indústria. As propriedades apresentadas por tais sistemas contribuem ativamente na produção de dispositivos eletro-óptico, como OLEDs, OFETs e células solares (semicondutores orgânicos). Os cristais líquidos são uma classe importante de materiais de baixa massa molecular devido às propriedades de ordem do estado sólido e fluidez do estado líquido. Com base neste contexto, este trabalho apresenta a síntese e caracterização das propriedades térmicas e óticas de três séries de compostos conjugados derivados de benzilidenocetonas 3,4-dissubstituídas. As estruturas dessas moléculas foram planejadas a fim de se obter materiais que exibam forma de bastão, requisito básico para a estrutura de cristais líquidos calamíticos. Os compostos sintetizados consistem de dibenzilidenocetonas 3-metoxi-4-substituídas com variadas cadeias alquílicas de 4, 10 e 12 átomos de carbono. Grupos cetonas cíclicos e acíclicos separam os anéis aromáticos. Os compostos foram caracterizados por espectroscopia no Infravermelho, Ressonância Magnética Nuclear de 1H e 13C. As propriedades térmicas foram investigadas através de DSC, MOLP e TGA. Das nove moléculas-alvo sintetizadas, uma apresentou mesomorfismo, três mantiveram estado isotrópico mesmo no resfriamento à temperatura ambiente, e os demais não apresentaram nenhum tipo de mesomorfismo. Os compostos finais apresentaram temperaturas de decomposição na faixa de 215 °C a 345 °C. Os estudos das propriedades óticas foram realizados por Espectroscopia de Ultravioleta em solução. As moléculas sintetizadas apresentaram forte absorção na faixa de 330 nm a 370 nm com elevada absortividade molar ( = 104 L.mol-1.cm-1) que, através de nossos estudos, são atribuídas às transições eletrônicas -*.

Orientador: Leila Aparecida Chiavacci / Banca: Renata Fonseca Vianna Lopez / Banca: Marcos Antonio Corrêa / Resumo: Nas últimas décadas, têm se observado um interesse crescente na inovação de sistemas nanoestruturados utilizados para a liberação prolongada de diversas substâncias. No caso de fármacos, as formulações de liberação prolongada apresentam diversas vantagens em relação às formas convencionais de administração, tais como alta eficiência de liberação, controle preciso da dosagem por períodos prolongados e diminuição da toxicidade. Dependendo da composição, uma mistura entre tensoativo, óleo e água podem formar diversos sistemas nanoestruturados com os mais variados níveis de organização estrutural, característica que interferi diretamente no processo de liberação. Neste trabalho esses sistemas foram obtidos pela construção de diagramas de fases, utilizando tensoativos com diferentes graus de hidrofilia, o PPG-5-Ceteth-20 e o Oleth 10, como fases oleosas o Ácido Oleico e o Miristato de Isopropila. Através dos diagramas foi possível observar diferenças significativas relacionadas com as características dos sistemas, devido à capacidade que o Oleth 10 como tensoativo e o Ácido Oleico como fase oleosa têm em diminuir a tensão interfacial, facilitando a formação de uma extensa região de sistemas transparentes. A caracterização da estrutura interna dos mesmos foi feita por microscopia de luz polarizada, espalhamento de raios-X a baixo ângulo (SAXS) e medidas reológicas. Através da microscopia foi possível identificar características isotrópicas e anisotrópicas, sendo posteriormente confirmadas pelo SAXS, o qual permitiu não só a identificação das nanoestruturas, mas também uma avaliação mais aprofundada sobre o nível de organização estrutural, principalmente dos arranjos líquido-cristalinos, característica que foi reforçada através das medidas reológicas, as quais proporcionaram uma... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In the last decades it has been observed a growing interest in nanostructure systems innovations, wich are response for control release of several substances. In the case of drugs, the formulations which promote the controlled release present many advantages against the conventional forms of administration, such as high release efficiency, precise dosage control for long periods and toxicity decreasing. Depending on the composition, a surfactants mixture, oil and water can form different nanostructured systems with the most different organization structure degrees, which can directly interfere in the global process of drugs release. In this paper the nanostructured systems were obtained through the building of phases diagrams, using surfactants with different hydrophilic degrees, the PPG-5-Ceteth-20 and the Oleth 10, as oil phases the Oleic Acid and Isopropil Miristate. It was possible to observe significant difference between the diagrams wich are related with the characteristics of the obtained systems, due to a higher capacity that Oleth 10 as a surfactant and the Oleic Acid as oil phase have in decreasing the interfacial tension, and consequently promoting a greater region of transparent systems. The internal structure of these systems was characterized by polarized light microscopy, small angle X-ray scattering (SAXS) and rheological measurements. Through the microscopy it was possible to identify the isotropic and anisotropic characteristics, being later confirmed by SAXS. This characterization through SAXS allowed not only the nanostructures identification, but also a more deeply evaluation on the structure degree, mainly on the arrangement of liquid-crystalline. The rheological test also provided a better understanding about the degree of internal structure of nanostructured systems, mainly those... (Complete abstract click electronic access below) / Mestre

Simulações de Dinâmica Molecular tornaram-se uma ferramenta indispensável no estudo de sistemas em fase condensada, incluindo sistemas líquido-Cristalinos, e na predição de propriedades dinâmicas. Cristais líquidos possuem um leque enorme de aplicações, mas o estudo teórico destes sistemas torna-se complicado devido ao seu tamanho, ao método utilizado para obtenção dos parâmetros do campo de força e, principalmente, à transferibilidade dos parâmetros para outro estado termodinâmico. Tendo isso em vista, este trabalho propõe uma metodologia para parametrizar campos de força derivados de cálculos mecânico-quânticos que possuam um grau de transferibilidade confiável. O sistema escolhido neste trabalho foi o 4’-Pentil- 4-Carbonitrila, também conhecido como 5CB, pois o mesmo já é utilizado em diversos aparelhos óptico-eletrônicos; a parametrização intramolecular foi feita com o programa JOYCE, e a intermolecular, com o programa PICKY. Os parâmetros intramoleculares obtidos mostraram uma boa descrição da geometria interna do sistema, contribuindo para a parametrização intermolecular, a qual obteve uma excelente descrição de propriedades termodinâmicas. Este trabalho corrobora para a hipótese de que campos de força derivados de cálculos mecânico- quânticos podem descrever diferentes fases termodinâmicas com um alto grau de confiabilidade. / Simulations using Molecular dynamics have become a powerful tool in the study of systems in condensed phase, including liquid-crystalline systems, and in the prediction of dynamical properties. Liquid Crystals have many applications, but the theoretical study of these systems is more complex because of their size, the method that was used in the force field parametrization and, mainly, because in most of the cases parameters cannot be transferred to another thermodynamical state. With that in mind, this work propose a methodology to parametrize force fields derived from quantummechanical calculations and which can be transferred to other thermodynamical state without losing important information. The chosen system in this work was the 4-Cyano-4’-Pentylbiphenyl, also known as 5CB, which have been used in many optical-electronic device and the intramolecular parametrization was done with the JOYCE program and the program PICKY was used in the intermolecular parametrization. The intramolecular parameters obtained show a good description of the internal geometry, contributes to the intermolecular parametrization, with we obtained an accurate description of the thermodynamical and physical chemical properties. This work corroborate to the hypothesis that force field derived from quantum-mechanical calculations can describe different thermodynamical states without losing important information.