Dissertations / Theses: 'Crystalline properties'

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Svensson, Erik. "Crystalline properties of starch." Lund : Lund University, 1996. http://books.google.com/books?id=VOdqAAAAMAAJ.

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Dimitrievska, Mirjana. "Crystalline and vibrational properties of kesterites." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/395179.

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The main objective of this thesis is to deepen the knowledge of fundamental properties of kesterite materials (Cu2ZnSnS4 and Cu2ZnSnSe4) and their solid solutions Cu2ZnSn(S,Se)4, which are used as absorber layers in solar cells. This principally included full characterization of structural and vibrational properties of these materials mainly using various Raman spectroscopy techniques. Special focus is put on the investigation of defect dynamics in kesterites, especially on the experimental identification of defects and their effect on the optoelectronic properties and thus the performance of solar cells devices. Additionally, among the objectives of the thesis was development of Raman based methodologies for the compositional assessment of these materials, as well as obtaining more information regarding the fundamental properties of ZnSSe secondary phase. The results were shown in the series of articles which have been published in high impact peer-review journals. In the first part of the thesis, a complete analysis of all Raman active modes of the stoichiometric Cu2ZnSnS4, Cu2ZnSnSe4 and Cu2ZnSn(S,Se)4 compounds was made using six different excitation wavelengths from near infrared to ultraviolet. Based on the first principle simulations, normal displacements of each Raman mode were calculated and provided insightful knowledge about the involvement of atoms in vibrations corresponding to different modes. Additionally defect dynamics in kesterite materials was explored. Asymmetry in the shape of the low frequency region of the main Raman modes has been observed for Cu2ZnSnS4 samples with different crystal quality. This has been attributed to phonon confinement effects which are arising from the loss of translational symmetry in the crystal caused by a high density of defects. Based on this model, a simple methodology independent of measuring conditions is proposed for the quantitative assessment of crystal quality through the correlation length. After this, the effect of specific defect clusters on the Raman spectra and optoelectronic properties was investigated. Combinatorial Cu2ZnSnSe4 thin films with lateral compositional gradients were synthesized and made into solar cell devices (around 200 cells per sample), in order to study the correlation between the optoelectronic properties and absorber composition. Furthermore, detailed analysis of the Raman spectra has allowed investigation of the changes in the relative intensity of Raman peaks in relation to the occurrence of different kinds of defect clusters. Finally, the influence of point defects and secondary phases on the performance of Cu2ZnSnSe4 devices was presented. Last part of the thesis was dedicated to development of a methodology for the quantitative assessment of the anion composition of Cu2ZnSn(S,Se)4 solid solutions using Raman spectroscopy. The methodology is based on the analysis of the integral intensity ratio of Raman bands sensitive to anion vibrations. Finally, a fundamental study, based on experimental and theoretical investigation, of the Raman resonance effects in ZnSSe solid solutions was presented. The Raman scattering intensities of LO ZnS-like and ZnSe-like phonon modes, corresponding to pure S and Se vibrations, respectively, were revealed to be significantly enhanced when excited with 325 nm excitation in the case of S vibrations, and with 455 nm in the case of Se vibrations. This behavior was explained by the interaction of the excitation photons with the corresponding S or Se electronic states in the conduction band, and further confirmed by first principles simulations. In conclusion, the works presented in this thesis are a significant contribution to the study of fundamental properties of materials in general, and kesterites materials in particular. Additionally, due to the unique approach of utilizing Raman spectroscopy with other characterization techniques, these methods could prove to be very successful in structure/function studies of other multinary compounds which are gaining increasing interest for electronic applications.
El objetivo principal de esta tesis es mejorar el conocimiento de las propiedades fundamentales de los compuestos de kesterita (Cu2ZnSnS4 and Cu2ZnSnSe4) y sus soluciones solidos Cu2ZnSn(S,Se)4 para uso como absorbedor en células solares. Esto constituye de la caracterización completa de las propiedades estructurales y vibracional utilizando la espectroscopia Raman. Adicionalmente, está el desarrollo de metodologías basado en Raman para la valoración composicional de estos materiales. Estos resultados están destacados en una serie de artículos publicados en revistas de peer-review de alto impacto. Un análisis completo de todos los modos activos de Raman de los compuestos estequiometricas de kesterita se realizó utilizando seis diferentes longitudes de onda de excitación, desde el infrarrojo hasta la ultravioleta. A partir de la base de simulaciones de primeros principios, los desplazamientos normales de cada modo Raman fueron calculados y dan un conocimiento útil sobre la participación de átomos en vibraciones correspondientes a diferentes modos. Un énfasis especial se da a la investigación de la dinámica de defectos en las kesteritas, en particular a la identificación experimental de los defectos y sus efectos sobre las propiedades optoelectrónicas, incluso el rendimiento, de dispositivos de células solares. También se desarrollo de una metodología para la valoración quantativa de la composición de aniones de soluciones solidos de Cu2ZnSn(S,Se)4 utilizando la espectroscopia Raman. Esta metodología se basa en la analisis de la intensidad integral de las bandas Raman más sensibles a vibraciones de los aniones. Por último, hay un estudio teórica y experimental del aumento en intensidad de los modos Raman de compuestos ZnSSe, bajo varias condiciones de resonancia, lo cual resulta en una mejora del conocimiento de la parte que juega los estados electrónicos de los calcogenuros en la interacción de fotón-materia. En conclusión, el trabajo presentado en esta tesis es una contribución significante al estudio de las propiedades fundamentales de los materiales en general, y los compuestos de kesterita en particular. Adicionalmente, debido al uso complementario de la espectroscopia Raman con otras técnicas de caracterización, estos métodos puedan resultar en ser muy útiles en estudios de estructura/función de otros compuestos multinarios, los cuales están ganado más interés para aplicaciones electrónicas.

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Budgell, Derek Richard. "Liquid crystalline properties of ethyl cellulose." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74271.

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The formation and chiroptical properties of liquid crystals of ethyl cellulose (EC) and some related polymers are investigated to determine which features affect the mesophase behaviour.
The onset of mesophase formation is studied by employing literature data on the viscosity/molar mass relationship of several cellulose derivatives, including EC in several solvents, to calculate their molecular dimensions by a recent hydrodynamic theory. The phase separation behavior is compared with the predictions of theories for both freely-jointed and wormlike chains.
The effects of solvent and degree of substitution (DS) on the cholesteric structure are assessed by studying the chiroptical properties using Circular Reflectance and Optical Rotatory Dispersion (ORD) techniques. The DS strongly influences the helicoidal twist sense, reflection wavelength and response of the reflection wavelength to changes in temperature. Mesophases and cholesteric films of the methyl and n-butyl derivatives of EC are also investigated. The ORD spectra of isotropic EC solutions are found to be strongly influenced by the solvent employed.

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Di, Lollo Antonio B. "Thermal and surface properties of crystalline and non-crystalline legume seed proteins." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59973.

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This work was devoted to the study of (a) the physico-chemical, functional, and structural properties of bean (Phaseolus sp.) protein isolates in relation to their microstructures, and (b) the effects of protein carbohydrate interactions on physico-chemical, functional, and structural properties. The contents of protein, and both total and individual sugars of alkali extracted (amorphous) and citric acid extracted (bipyramidal and spheroidal) proteins from Phaseolus vulgaris (white kidney and navy) and Phaseolus lutanus (baby lima and large lima) beans were determined. The proteins were subjected to differential scanning calorimetry, and measurements of surface tension (air-water interface), surface hydrophobicity, and foam expansion. Structural analysis of the proteins were performed using Fourier transform infrared (FT-IR) spectroscopy. Enzymatic and chemical deglycosylation was performed on a white kidney bean protein isolate.
Glucose and mannose were the major sugars found in the isolates. Bipyramidal and spheroidal microstructures with higher protein contents generally had greater mannose content and lower glucose content. Differences in enthalpy of denaturation $( Delta$H), surface tension decay curves, surface hydrophobicities, and foam expansions were observed with isolates of different microstructures. Corresponding differences in molecular structure were not, however, detected by FT-IR spectroscopy. Using statistical analysis, a relationship between foam expansion and the $ Delta$H, solubility, surface hydrophobicity and surface tension of the isolates was obtained. Preliminary results suggest that the removal of carbohydrate influenced the physico-chemical properties of the protein.

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Heng, Jerry Yong Yew. "Anisotropic surface properties of crystalline pharmaceutical solids." Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/8843.

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Thies, Jens Christoph. "Optical properties of chiral liquid crystalline polymers." Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/590.

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Haws, Christine Margaret. "Selected physical properties of liquid crystalline polysiloxanes." Thesis, Durham University, 1989. http://etheses.dur.ac.uk/6496/.

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The static and dynamic electrical behaviour, the electrical conductivity, the macroscopic viscosity and the optical transmission characteristics of side chain polysiloxane liquid crystal polymers (LCPs) have been studied. Particular emphasis has been placed on the study of the molecular dynamics using dielectric relaxation spectroscopy and the low field (AC) and high field (DC) conductivity, with the intention of relating structural variations to the behaviour of these materials, and of identifying the most appropriate LCPs for use in practical optical storage devices. The effect on the molecular dynamics of the polymer backbone and the core, spacer and end groups of the mesogenic units was investigated. The LCP responses were shown to be broadly similar to those of low molar mass liquid crystals, though with longer relaxation times. The dynamic responses of structurally different LCPs were shown to be related when these were observed at a temperature referenced to the glass transition temperature. Values of the static permittivity of several LCPs have also been measured and tabulated. Low field electrical conductivity measurements were used to show that the magnitude of the conductivity was comparable to that of commercial liquid crystals. A method was identified whereby the conductivity of different LCPs could be compared. The texture of the measuring electrode surface was found to play an important role in determining the impedance of electrical double layers formed near the surface of the sample, with smooth polymer based surfactants reducing the formation of space charge. High field DC conductivity measurements showed that Schottky-type charge emission occurred at the electrodes at elevated temperatures, except when the smooth polymer based surfactants were present. This was probably a result of the reduction in the local field near the electrode due to a better physical match at the LCP/surfactant interface. The bulk viscosity of mixtures of an LCP and commercial liquid crystal were also measured and the results extrapolated to the viscosity of the LCP. The relationship between electrical conductivity and bulk viscosity was examined. The optical absorption spectra of blue pleochroic dyes have been measured to identify appropriate dyes for use with LCPs in laser written optical memories. The stability of the alignment of selected LCPs with time and temperature was also observed optically.

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Sweed, Muhamed. "Free volume properties of semi-crystalline polymers." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6597.

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Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2011.
ENGLISH ABSTRACT: Positron annihilation lifetime spectroscopy (PALS) is well established as a novel method currently available for the study of polymers at a molecular level because of its sensitivity to the microstructural changes in the polymer matrix. The technique provides unique, but limited, information of the solid state structure – primarily on the nature of the free volume (or unoccupied space) in the polymer due to the less dense packing of polymer chains relative to in other solid materials. In the case of completely homogeneous polymer materials the measurement and interpretation of the positron annihilation parameters is relatively simple. However, in the case of polymers with more complex morphologies the situation becomes less clear. This is due to the possibility of the formation, localization and subsequent annihilation of o-Ps (ortho-positronium) within different areas of the complex morphology. This can result in more than one o-Ps lifetime component being present, and each of the different components corresponds to areas with differing types and amounts of 'open spaces'. In this study a detailed and systematic approach was taken to study the positron annihilation parameters in various semi-crystalline polymers and to correlate these to the chain structure and morphology of the materials. The study focused specifically on polyolefin polymers as these are the most widely used semi-crystalline materials, but more importantly, they offer the possibility to produce a variety of morphological complexity by simple manipulation of the chain structure – while there is essentially no difference in the chemical composition of the materials. The copolymers were selected to study the influence of short-chain branching (amount and length), short-chain branching distribution and tacticity on the morphology, and subsequent positron annihilation lifetime parameters. Three separate topics were addressed. First, preparative temperature rising elution fractionation was used to isolate polymer samples that are homogeneously crystallisable and to produce a series of polymers with differing chain structure and resultant morphologies. Second, additional series were produced by removing specific crystallisable fractions from the bulk materials. Third, the temperature variation of the samples as they approach and go through the crystalline melting point was studied. All the raw positron data were found to be best fitted with a four-component positron annihilation lifetime analysis. The longest lifetime (which is attributed to annihilation of o-Ps in the amorphous phase of the materials) showed systematic variations with the degree and nature of the short-chain branding, tacticity variation, a combination of both short-chain branching and tacticity, and changes in the amorphous phase as a result of heating. The third lifetime component (which is attributed to o-Ps annihilation in or around the crystalline areas of the materials) showed less variation across the sample series. Typically, greater variations were observed in the propylene copolymers than in the ethylene copolymers, which are reflective of the more complex chain structure and corresponding morphology in the propylene copolymer series. Direct evidence for a contribution from the nature of the amorphous phase to the bulk microhardness of the sample was also found.
AFRIKAANSE OPSOMMING: Positronvernietigingsleeftydspektroskopie (PALS) is goed gevestig as ‘n nuwe metode vir die studie van polimere op molekulêrevlak agv die sensitiwiteit van die metode vir mikrostrukturele veranderings in die polimeermatriks. Hierdie tegniek verskaf unieke, maar beperkte, inligting aangaande die vastetoestandstruktuur – veral aangaande die aard van die vryevolume (of onbesette spasie) in die polimeer as gevolg van die minder digte verpakking van polimeerkettings relatief tot in ander vastestowwe. In die geval van volledig homogene polimeriese materiale is die meet en interpretasie van die positronvernietigingsparameters relatief eenvoudig. Maar in die geval van polimere met meer komplekse morfologieë is die situasie minder duidelik. Die rede hiervoor is die moontlikheid vir die formasie, lokalisering en gevolglike vernietiging van o-Ps (orto-positronium) in die verskillende areas van die komplekse morfologie. Dit kan tot gevolg hê dat meer as een o-Ps komponent teenwoordig is en waar elk van die verskillende komponente ooreenstem met areas met verskillende tipes en hoeveelhede 'oop spasies'. In hierdie studie is ‘n sistematiese, in-diepte benadering gebruik om die positronvernietigingsparameters in verskeie semikristallyne polimere te bestudeer en hulle te korreleer met dié van die kettingstruktuur en die morfologieë van die materiale. Hierdie studie het spesifiek gefokus op poliolefiene aangesien hulle die mees algemene semikristallyne materiale is wat gebruik word en, nog meer belangrik, hulle bied die geleentheid om verskeie komplekse morfologieë te lewer dmv eenvoudige manipulasie van die kettingstrukture – terwyl daar basies geen verandering in die chemiesesamestelling van die materiale is nie. Die kopolimere is gekies om die invloed van kort-ketting vertakking (lengte en hoeveelheid), kort-ketting vertakking verspreiding en taktisiteit op die morfologie en vervolgens die positronvernietigingsleeftyd parameters te bestudeer. Drie onderwerpe is aangespreek. Eerstens, preparatiewe temperatuurstygingelueringsfraksionering (prep-TREF) is gebruik om polimeermonsters wat homogeenkristalliseerbaar is te isoleer om sodoende 'n reeks polimere met verskillende kettingstrukture, en gevolglike morfologieë, te lewer. Tweedens, 'n addisionele reekse monsters is berei deur die verwydering van spesifieke kristalliseerbare fraksies vanaf die grootmaatmonsters. Derdens, die temperatuurverandering van die monsters wanneer die monsters naby aan die kristallyne smeltpunt is en wanneer hulle deur die kristallyne smeltpunt gaan is bestudeer. Daar is bevind dat alle rou positrondata ten beste gepas het in 'n vier-komponent positronvernietigingsleeftydanalise. Die langste leeftyd (wat toegeskryf is aan vernietiging van o-Ps in die amorfe fase van die materiaal) het sistematiese variasies getoon met die volgende: hoeveelheid en aard van die kort-kettingvertaking, verandering in taktisiteit, 'n kombinasie van beide kort-kettingvertakking en taktisiteit en veranderings in die amorfiesefase as gevolg van verhitting. Die derde leeftyd komponent (wat toegeskryf is aan die o-Ps vernietiging in of rondom die kristallyne areas van die materiale) het minder variasie in hierdie reeks monsters getoon. Daar is tipies meer variasie waargeneem in die propileenkopolimere as in die etileenkopolimere, wat ’n weerspieëling is van die meer komplekse kettingstruktuur en ooreenstemmende morfologie in die propileenkopolomeerreeks. Direkte bewys vir 'n bydrag van die aard van die amorfe fase tot die grootmaat mikrohardheid van monsters is ook bevind.

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JÃnior, Diniz Maciel de Sena. "Vibrational and Thermal Properties of Crystalline Topiramate." Universidade Federal do CearÃ, 2008. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=1372.

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FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico
The scientific interest on molecular crystals stems from their great versatility and ease of processing. For pharmaceutically active ingredients, the structure-activity relationship is of major importance. Topiramate, a white and crystalline solid, is a powerful drug efficiently employed to control epilepsy symptoms. The mechanism of action involves a negative modulatory effect on the AMPA/kainate subtypes of glutamate receptors and some types of voltage-gated Na+ and Ca2+ channels, and a positive modulatory effect on some types of GABAA receptors and at least one type of K+ channels in neurons. Despite its pharmacological attributes, the lack of publications regarding its physical-chemical properties in the literature is apparent. In order to fill this gap, a research comprising vibrational spectroscopy techniques (Raman and infrared), thermal analysis (TGA/DTA/DSC), and theoretical calculations, was carried out. With the aid of calculations employing density functional theory (DFT), most of the observed vibrational bands is assigned. Consideration of Raman spectra recorded at temperatures above and below room temperature, as well as under high hydrostatic pressures, indicated maintenance of the orthorhombic crystalline structure under the diverse thermodynamic conditions employed. Thermal analysis, however, showed that, after the melting point, the sample undergoes decomposition in a process comprising three stages, possibly initiated with loss of the sulfamate group by the molecule. This event inspired a theoretical study aimed at promoting the sulfamate group bond breakage in a controlled way by employing a laser instead of heat. This was accomplished by quantum dynamics simulations which showed that, by using a set of ultrashort pulses in the infrared region, it is possible to reach levels close to 70 % dissociation in less than 3 ps.
O interesse cientÃfico pelos cristais moleculares resulta da facilidade de processamento destes materiais, e de sua grande versatilidade. No caso de drogas, a relaÃÃo entre estrutura e atividade Ã de suma importÃncia. Topiramato, um sÃlido branco e cristalino, Ã um fÃrmaco utilizado com bastante eficiÃncia para controlar os sintomas da epilepsia. O mecanismo de aÃÃo envolve um efeito modulatÃrio negativo nos receptores de glutamato do subtipo AMPA/kainato e alguns tipos de canais de Na+ e Ca2+ voltagem-dependentes, bem como um efeito modulatÃrio positivo em alguns tipos de receptores GABAA e pelo menos um tipo de canal de K+ nos neurÃnios. A despeito de suas qualidades farmacolÃgicas, a escassez de trabalhos relacionados Ãs suas propriedades fÃsico-quÃmicas na literatura Ã evidente. Para ajudar a preencher esta lacuna, uma investigaÃÃo envolvendo tÃcnicas de espectroscopia vibracional (Raman e infravermelho), anÃlises tÃrmicas (TGA/DTA/DSC), e cÃlculos teÃricos, foi realizada. Com a ajuda de cÃlculos empregando a teoria do funcional de densidade (DFT), a atribuiÃÃo da maioria das bandas vibracionais observadas foi realizada. A observaÃÃo dos espectros Raman obtidos em temperaturas acima e abaixo da ambiente, bem como sob altas pressÃes hidrostÃticas, indicou que a estrutura cristalina ortorrÃmbica Ã mantida nas diferentes condiÃÃes termodinÃmicas empregadas. A anÃlise tÃrmica, entretanto, mostrou que, apÃs a fusÃo, o material sofre decomposiÃÃo em um processo que envolve trÃs etapas, possivelmente iniciado com a perda do grupo sulfamato pela molÃcula. Este fato motivou um estudo teÃrico a fim de modelar a quebra da ligaÃÃo do sulfamato de maneira controlada, utilizando um laser em lugar de calor. Isto foi realizado com simulaÃÃes de dinÃmica quÃntica, que mostraram que, atravÃs da utilizaÃÃo de uma combinaÃÃo de pulsos ultracurtos na regiÃo do infravermelho, Ã possÃvel atingir nÃveis prÃximos a 70% de dissociaÃÃo em menos de 3 ps.

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Watson, Greg. "Spectral properties of periodically modulated systems." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302889.

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Wang, Haopeng. "Confined crystallization, crystalline phase deformation and their effects on the properties of crystalline polymers." Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1246041849.

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Vinh. "Optical properties of isoelectronic centers in crystalline silicon." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/75308.

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Sheppard, O. "Structural and liquid crystalline properties of ionic liquids." Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431482.

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Halliwell, Rebecca Amy. "Control of crystalline particle properties by spray drying." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28652.

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Although spray drying has been common place in the pharmaceutical industry for decades, the integration of the technique into continuous manufacturing can offer an extensive array of particle engineering applications. Continuous manufacturing aims to deliver consistent and sustainable drug products of a better and higher quality. Spray drying is a continuous processing technique typically adopted for amorphous solid production. However, the unique conditions of the technique can also can be adapted and applied to crystallisation enabling particle property engineering. The semi-continuous lab-scale Büchi B-290 Mini spray dryer is widely available and has been previously studied extensively for particle engineering and as a development platform for applications including pulmonary drug delivery, sustained release formulations and amorphous solid dispersions. The focus of this work is to engineer and enhance particle properties through the use of the Büchi spray dryer. Particle formation has been investigated, with specific focus in terms of polymorph formation in carbamazepine, to develop a predictive model for crystallisability and for co-spray drying of metformin hydrochloride with mannitol and lactose. Particle formation has been described in terms of theoretical drying kinetics and combined with off line characterisation to determine size and form of product. The metastable polymorph, form IV, of carbamazepine was made reproducibly by spray drying with the combination of rapid evaporation and product isolation shown to be crucial to prevention of solution mediated transformation. The application of non-invasive Raman spectroscopy was also utilised to assess product form. A crystallisability predictive model based on a Random Forest method was successfully produced through combining molecular descriptors with published and experimental outcomes. The model provided up to 79 % accuracy in predicting whether an amorphous or crystalline product would be expected from rapid drying. This shows considerable utility in streamlining process development. Finally, co-spray drying in the Büchi system using a three-fluid nozzle was used to produce multicomponent composite particles comprising of two crystallite phases. The effect of process configuration and material properties on the resultant particles was assessed using particle sizing, SEM, XRPD and Raman mapping. The results were compared on the basis of theoretical drying kinetics to assess the ability to predict the resultant particle morphology. Four multicomponent composite particles were produced by co-spray drying from metformin hydrochloride (MF), mannitol and lactose. MF-mannitol composites produced three-phase physical mixtures with both components present on the particle surfaces. The particle surface compositions were contradictory to the expected particle outcomes from the drying parameters. MF-lactose composite particle also produce three-phase physical mixtures with a relatively equal distribution of components present on particle surface. This is consistent with the expected particle from the drying parameters. The different particle outcomes suggest that co-spray drying of miscible multicomponent feeds using the three-fluid nozzle is highly dependent on the drying parameters for each component due to equal mixing of the feed at atomisation of droplets.

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Banach, Michael James. "Alignment properties of liquid crystalline conjugated polymer films." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619834.

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Gabaston, Laurence Isabelle. "Synthesis and properties of liquid crystalline conducting polymers." Thesis, Kingston University, 1996. http://eprints.kingston.ac.uk/20594/.

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Novel conducting polyanilines which are thermoplastic and have mesogenic side-chains have been synthesised and investigated in order to study the use of liquid crystal alignment to produce higher conductivity. The backbone was based on ortho-substituted aniline polymers. A large variety of suitable ortho-substituted nitrobenzene precursors with liquid crystalline properties were synthesised and investigated by microscopy and differential scanning calorimetry. A study of the 4-methoxyphenyl 4-[x-(2-nitrophenoxy)alkoxy] benzoate series (x = 2-10) showed that only the molecules with even spacer lengths were liquid crystalline whereas the ones with odd spacer lengths were not. All the even molecules were nematic in character. Some substituted biphenyl nitrobenzenes were also synthesised and 4-cyano 4'-[6-(2-nitrophenoxy)hexoxy]biphenyl exhibited a monotropie nematic phase. A large variety of ortho-substituted nitrobenzenes with transition temperatures above 100°C were also synthesised. Depending on their structure, nematic as well as smectic phases were characterised. The ortho-substituted nitrobenzene molecules were subsequently reduced to the required anilines. Their liquid crystal properties were similar to their respective nitro-compounds.These liquid crystalline aniline monomers were chemically polymerised by use of an emulsion system. The polymers obtained were fully characterised by spectroscopic analysis, and were a head-to-tail emeraldine type substituted polyaniline. The physical properties of these potentially liquid crystalline conducting polymers were fully investigated. They were found to be soluble in DMF, DMSO, THF and CHCI3• UV/visible study revealed an average band gap of 3.4 eV. Gel permeation chromatography analysis showed the presence of oligomers and higher polymers in smaller proportion for each samples. These polymers were also structurally stable up to 300°C. Polarising hot-stage microscopy and differential scanning calorimetry showed the existence of liquid crystal properties for two of these polymers namely : poly[2-(hexoxy)-6-(4- biphenyloxy-4' carboxylic acid)]aniline and poly[2-[4-cyanophenyl-4-carboxylate 6-(4'-oxybiphenyl)hexoxy aniline. In fact, a nematic phase was exhibited for the carboxylic acid polymer between 225 and 261°C and between 120 and 175°C for the ester polymer. Study of their electrical conductivities showed some semi-conducting characteristics with values as high as 1.2xlO-3 S ern" for the H2S04 vapour doped carboxylic acid polymer and equal to 8xlO-6 S cm" for the HCI doped ester poÍymer. An increase in conductivity values was also observed as the temperature reaches the nematic liquid crystal transitions, demonstrating the effect of the mesogenic groups on the ordering of the polymer backbone. Laser alignment of these two liquid crystal semi-conducting polymers was also carried out. A conductivity anisotropy was observed along the laser written samples. This technique could also be of great potential interest as a method of localised conductivity enhancement.

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Lambe, Gillian Jane. "Synthesis and properties of liquid crystalline conjugated polymers." Thesis, Kingston University, 2003. http://eprints.kingston.ac.uk/20712/.

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Novel conducting polythiophenes, which have mesogenic side-chains have been synthesised and investigated in order to study their liquid crystallinity and its possible effects on electronic conductivity. The backbone was based on substituted polythiophenes. Four main types of liquid crystalline conjugated polymers were investigated: l Polymers without liquid crystal groups attached 2 Polymers with laterally attached liquid crystal groups 3 Polymers with terminally attached liquid crystal groups 4 Polymers with terminally attached liquid crystal groups that have potential negative dielectric anisotropy A large variety of suitable thiophene-substituted precursors with potential liquid crystalline properties was synthesised and investigated by optical microscopy and differential scanning calorimetry. Williamson ether synthesis and boronic acid coupling chemistry were mainly used to synthesise the polymer precursors. Some of these monomers proved difficult to homopolymerise due to the large bulky . laterally attached moieties, therefore copolymerisations with 3-alkylthiophenes were carried out. Cyclic voltammetry of the liquid crystalline substituted thiophene precursor was investigated but even when redox peaks were observed. no polymer film was formed. Therefore these liquid crystalline conjugated polymers/copolymers were chemically synthesised by free radical polymerisation using FeCh and then synthetically modified. The polymers obtained were fully characterised by spectroscopic analysis and the physical properties of these potentially liquid crystalline conjugated polymers were investigated. Comparative studies of the laterally-attached liquid crystalline conjugated copolymers,poly[(I-(3-thiophenemethoxy)-6-(4-n-hexoxy-2-oxybenzoic acid)hexane-co-(3-hexylthiophene)] and of its terminally attached analogue poly[(I-(3-thiophenemethoxy )-6-( 4-oxybenzoic acid)hexane )-co-(3- hexylthiophenej], revealed that the conductivity of the former was much greater than the latter. Also observed was the noticeable increase in conductivity when the copolymers were converted from the ester form poly[(I-(3- thiophenemethoxy)-6-( methyl 4-n-hexoxy-2-oxybenzoate )hexane )-co-(3- hexylthiophene)] to the liquid crystal acid form poly[(I-(3-thiophenemethoxy)-6- (4-n-hexoxy-2-oxybenzoic acid)hexane )-co-(3-hexylthiophene)]. It became evident that an alkyl spacer was necessary to attach the lateral liquid crystal group. as the alkyl chains provided enough space for the bulky group to orientate into position. However copolymer ratio studies revealed that the ratio of alkyl chain to liquid crystal groups did not significantly affect the overall conductivity of the copolymers for this class of compounds. Also the electrical conductivities as a function of temperature for some undoped LC copolymers of poly[(I-(3- thiophenemethoxy)-6-( 4-n-hexoxy-2-oxybenzoic acid)hexane )-co-(3- hexylthiophene)] increase with increasing temperature. The temperature range in which these increases occur corresponds to LC transitions in the differential scanning calorimetry and by polarising hot-stage microscopy.

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18

Mogri, Zen. "Gas transport properties of side-chain crystalline polymers /." Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008396.

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19

Park, Seung Chul. "Study of optical properties of multi-crystalline Si and of heavily dislocated single-crystalline Si." Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314286.

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20

Shepherd, James Ellison. "An internal state variable based constitutive model for semi-crystalline polymers." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17638.

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21

Jones, Christopher Wynne. "Structural and electronic properties of mixed metal oxides." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235645.

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22

Claesson, Hans. "Synthesis and Properties of Branched Semi-Crystalline Thermoset Resins." Doctoral thesis, KTH, Fibre and Polymer Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3583.

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This thesis describes the synthesis and characterization ofbranched semi-crystalline polymers. Included in this work isthe SEC characterization of a series of dendrimers. Thebranched semi-crystalline polymers were synthesized in order toinvestigate the concept of their use as powder coatings resins.This concept being that the use of branched semi-crystallinepolymers in a UV-cured powder coating system may offer a lowertemperature alternative thus allowing the use of heat sensitivesubstrates and the added benefit of a reduced viscositycompared to linear polymers.

A series of branched poly(ε-caprolactone)s (PCL)(degree of polymerization: 5-200) initiated from hydroxylfunctional initiators were synthesized. The final architectureswere controlled by the choice of initiator structure;specifically the dendritic initiators yielded starbranchedPCLs while the linear initiator yielded comb-branchedPCLs. The dendritic initiators utilized were: (1) a3rd-generation Boltorn H-30, commercially availablehyperbranched polyester with approximately 32 hydroxyl groups,(2) a 3rd-generation dendrimer with 24 hydroxyl groups, and (3)a 3rd-generation dendron with 8 hydroxyl groups. Linear PCL wassynthesized for comparison. All dendritic initiators are basedon 2,2- bis(methylol) propionic acid. The comb-branchedpolymers were initiated from a modified peroxide functionalpolyacrylate. The resins were end-capped withmethylmethacrylate in order to produce a cross-linkable system.The polymers and films were characterized using 1H NMR, 13CNMR, SEC, DMTA, DSC, FT-IR, FT-Raman, rheometry and a rheometercoupled to a UV-lamp to measure cure behavior.

The star-branched PCLs exhibited considerably lowerviscosities than their linear counterparts with the samemolecular weight for the molecular region investigated (2-550kg mol-1). It was also found that the zero shear viscosityincreased roughly exponentially with M.

The PCL star-branched resins are semi-crystalline and theirmelting points (Tm) range from 34-50°C; films can beformed and cured below 80°C. The viscoelastic behaviourduring the cure showed that the time to reach the gel point, afew seconds, increased linearly with molecular weight. Thecrossover of Gand Gwas used as the gelpoint. Measurement of mechanical properties of films showedthat the low molecular weight polymers were amorphous whilethose with high molecular weight were crystalline after cure.The polymerization of 5,5-dimethyl-1,3-dioxane-2-one (NPC) fromoligo- and multifunctional initiators was evaluated utilizingcoordination and cationic polymerization. Two tin basedcatalysts, stannous(II) 2-ethylhexanoate and stannous(II)trifluoromethane sulfonate, were compared with fumaric acid.Fumaric acid under bulk conditions resulted in lowerpolydispersity and less chance of gelling. The synthesis ofstar-branched polymers was confirmed by SEC data. The starpolymers exhibited a Tg at 20-30°C and a Tm at about100°C.

All semi-crystalline resins exhibited a fast decrease inviscosity at Tm. Blends of combbranched semi-crystalline resinsand amorphous resins exhibited a transition behavior inbetweenthat of pure semi-crystalline resins and that of amorphousresins.

The SEC characterization of a series of dendrimers withdifferent cores and terminal groups showed that the core had animpact on the viscosimetric radius of the core while theterminal groups appeared to have no effect.

Keywords:star-branched, semi-crystalline,comb-branched, ring-opening polymerization,poly(ε-caprolactone), dendritic, thermoset, lowtemperature curing, powder coating, UVcuring,poly(5,5-dimethyl-1,3-dioxane-2-one), size exclusionchromatography, rheology, dendritic aliphatic polyester

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23

Mcguire, Janine Gale. "Synthesis and properties of potentially liquid crystalline phosphorus compounds." Thesis, University of Central Lancashire, 2000. http://clok.uclan.ac.uk/20138/.

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Traditionally it was considered necessary for molecules to be either rod or disc shaped to fulfil the requirements necessary for liquid crystalline phase formation. However, recent moves away from these traditional theories have led to the discovery of molecules possessing geometries such as tetrahedral and even octahedral producing mesogenic phases. One molecular geometry not yet shown to display liquid crystalline behaviour is trigonal pyramidal. Group V elements exhibit such geometry. This thesis reports the synthesis of a number of novel phosphorus(IIl) molecules and an investigation into their possible liquid crystalline phase behaviour. Trigonal pyramidal phosphines together with the corresponding tetrahedral phosphine oxides, with three alkoxybiphenyl groups attached to a central phosphorus atom, were synthesised with varying alkyl chain lengths between C1-C22. Investigation into liquid crystalline behaviour by both sets of compounds failed to demonstrate any mesophase formation. However, tri(nonyloxybiphenyl)phosphine oxide did show evidence of crystal to crystal transitions, often seen as a precursor to liquid crystaffine behaviour. Conversion of the phosphorus molecules into a more traditional linear shape by the replacement of an alkoxybiphenyl group with a smaller alkyl or phenyl group was also undertaken to investigate possible liquid crystalline behaviour, although none was observed. Attempts were also made to extend the length of the groups attached to the phosphorus atom to a tri-phenyl ring system incorporating an azo linking unit, which has often been shown to demonstrate mesophase behaviour. This led to the synthesis of a new series of compounds, phenyl (4-alkoxyphenylazo)benzoates, which demonstrated both nematic and smectic C liquid crystalline phases. Unfortunately, synthesis of the desired phosphorus was not achieved. Di(alkoxybiphenyl)phosphine oxides separated by an alkyl spacer group, were synthesised in an attempt to produce H-shaped molecules, an arrangement that would be intermediate between rod and disc shaped molecules. Again, liquid crystalline behaviour was not observed. A series of mixed butyl and methyl phosphonium nonadecafluorodecanoates were shown to produce lyotropic liquid crystalline phases in accordance with those observed for the equivalent ammonium compounds.

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24

Whitehead, Katherine Suzanne. "Polarised light emitting properties of liquid crystalline conjugated polymers." Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269317.

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25

Sakaida, Shun. "Stimuli-responsive properties of a downsized crystalline coordination framework." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263346.

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26

Zhang, Heping. "Structure and properties of oriented thermotropic liquid crystalline polyesters and polyamides." Thesis, University of Leeds, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305812.

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27

Nitsche, Robert. "Optical Properties of Organic Semiconductors: from Submonolayers to Crystalline Films." Doctoral thesis, [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=979835186.

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28

Nitsche, Robert. "Optical Properties of Organic Semiconductors: from Submonolayers to Crystalline Films." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1147356837431-39487.

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We have measured the optical properties of films of the organic semiconductors PTCDA (3,4:9,10-perylene-tetracarboxylic dianhydride) and HBC (peri-hexabenzocoronene), prepared by Organic Molecular Beam Expitaxy (OMBE), on different substrates by means of Differential Reflectance Spectroscopy (DRS). The optical setup enables us to directly follow the thickness dependent optical properties of the organic films, starting from submonolayer coverage up to thicker films on the order of 20 monolayers (ML) film thickness. Due to the different optical nature of the different substrates used, i.e., mica, glass, Au(111), and HOPG, the direct interpretation of the DRS signal is not feasible. Therefore, we have proposed a method by which the calculation of the optical constants n (index of refraction) and k (absorption index) of thin films on arbitrary substrates from just one spectral measurement (in our case the DRS) becomes possible. The results fulfill a priori a Kramers-Kronig consistency and no specific model is needed to express the spectral behavior of the optical constants. Based on our method, we have successfully calculated the optical constants, and therefore the absorption behavior, of films of different thickness of PTCDA on mica, glass, Au(111), and HOPG, as well as of HBC on mica, glass, and HOPG. Extrinsic effects due to island growth or the presence of a polarizable substrate (screening) have been accounted for. We have introduced a finite dipole model which considers the extended geometry and anisotropy of the organic molecules. The calculated absorption behavior is discussed in great detail in terms of spectral changes with varying film thickness, different growth modes, degree of ordering of the films, interactions with the substrates and oscillator strength. A direct observation of a monomer-dimer transition in solid films could be observed for the first time. Our results indicate an exciton delocalization over about 4 molecules for both molecules.

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29

Dikeakos, Maria. "Electronic properties of amorphous and crystalline FexCo1-x-Zr2 alloys." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20141.

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The electronic contribution to the resistivity rho and its temperature dependence were investigated for amorphous and crystalline [Fe xCo1--x] 33.3Zr66.7 (0 ≤ x ≤ 1) alloys in the temperature range 80--300 K. As Fe-rich compositions may exhibit spin fluctuation effects, transport properties were not studied below 80 K where spin fluctuation effects must be taken into consideration. The compositional and structural integrity of the samples was verified by means of X-ray diffractometry, electron-microprobe analysis, and differential scanning calorimetry. It was also confirmed that the first crystallization product for all the compositions is the face-centered cubic phase with the NiTi2-type structure. A true comparison between amorphous and crystalline transport properties was thus possible. For the metallic glasses, it was observed that rho( T) had a temperature dependence of the form: A + Bexp(--T/Delta) in agreement with Mizutani who proposed this relation for glasses containing a significant number of d-electrons at EF. The characteristic temperature, Delta, was found to be related to the Debye temperature, theta D, and the parameter B to the electronic specific heat coefficient, gamma. The resistivity data for the crystalline tenary compounds exhibited a (c -- bT + aT2)-dependence. Both the glasses and their crystalline counterparts were characterized by negative temperature coefficients of the resistivity, alpha. However, for the glasses, alpha increased as the Fe content increased whereas for the crystalline compounds alpha decreased as the Fe content increased.

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30

Rowland, Joanne. "Assessing changes in the surface properties of a crystalline material." Thesis, University of London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533545.

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31

Carpentier, Alice Ursula. "Hyperbranched polysiloxysilanes-liquid crystalline core-shell structures : preparation and properties." Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/610.

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32

Pickles, Adrian Philip. "The rheology, properties and morphology of thermotropic liquid crystalline polymers." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317227.

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33

Barlow, Lyndsey J. "Thermal, mechanical and electrical properties of liquid crystalline polymer electrolytes." Thesis, University of Aberdeen, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401497.

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It is generally accepted that ion transport in polymer electrolytes is strongly coupled to the local viscosity of the host polymer and that, in most cases, appreciable ionic conductivity below the glass transition temperature is not observed. Recent literature suggests that this may not always be the case and examples of polymer electrolytes exhibiting ionic conductivity decoupled from the polymeric motions have been reported. This thesis investigates one such system, a liquid crystalline polymer electrolyte, which has been reported to show measurable conductivity in the sold phase. The aim is to investigate such decoupled behaviour, how it may be optimised and to understand the conductivity mechanism. The thermal, mechanical and electrical properties of lithium perchlorate and lithium triflate complexes of a liquid crystalline polymer and its non-liquid crystalline analogue have been investigated. These studies suggest that the conductivity is not in fact decoupled from the local motions of the polymer. Selected complexes are then examined further and conductivities measured under variable pressure. From these data, activation energies, volumes and decoupling constants are calculated. These results show that, although not fully coupled, these complexes cannot be considered to exhibit decoupled conductivity and, in fact, the non-liquid crystalline electrolytes actually show a greater tendency towards decoupled behaviour than their liquid crystalline counterparts. In the final chapter, the two polymers are complexed with lithium trifluoromethanesulphonyl imide, a salt that has been reported to give enhanced conducivities. It is found that using this salt does indeed raise conductivities, but also reduces tendencies towards decoupled behaviour.

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34

Thadani, Shalini B. "Effect of crystalline-phase crosslinking on thermomechanical properties of a diacetylene-containing polyamide fiber." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/9252.

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35

Khamvongsa, Bryan. "Molecular control of liquid crystalline orientation of poly(2,6-benzoxazole)." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/8567.

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36

Greenstein, Abraham. "Analysis of thermal conductivity models with an extension to complex crystalline materials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24710.

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Thesis (Ph.D.)--Mechanical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Graham, Samuel; Committee Co-Chair: Nair, Sankar; Committee Member: Grover - Gallivan, Martha; Committee Member: McDowell, David; Committee Member: Schelling, Patrick; Committee Member: Zhang, Zhuomin

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37

Roso, Casares Sergio. "Synthesis and gas sensing properties of single crystalline metal-oxide nanostructures." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/402468.

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A la present tesis doctoral, s'han produït diferents tipus de nanoestructures basades en òxids metàl·lics, com per exemple nanofils de ZnO i octaedros d'In2O3, utilitzant el mètode de Deposició Química de Vapor (CVD) a altes temperatures. Per a la detecció d'òxid de nitrogen, s'ha descobert que la resposta dels nanofils d'ZnO està directament relacionada amb la quantitat de defectes presents en el material. Com més gran es el nombre de defectes, major és la resposta al diòxid de nitrogen. Tanmateix, per a la detecció d'etanol, la mostra que contenia un nombre mig de defectes, va ser la que dóna millors resultats. Pel que fa als octaedres de In2O3, podem dir que els octaedres d'In2O3 pur són excel·lents candidats per a la detecció de NO2, ja que tenen una excel·lent sensibilitat (0.43 ppb-1) a baixes temperatures (130ºC), mentres que la resposta a altres gasos com H2 és dos ordres de magnituds inferior en les mateixes condicions. A més a més, en presencia d'humitat, s'incrementa la sensibilitat a NO2 i, a la vegada, es redueix la sensibilitat a H2, pel que la selectivitat a NO2 també es veu incrementada. Finalment, utilitzant l'espectroscopia DRIFT, s'ha analitzat l'In2O3 expost a 1 ppm de NO2 a diferents temperatures i s'ha descobert que el mecanisme proposat per a descriure el procés de sensat es bastant més complicat del que s'ha reportat fins ara. Com a resultat de tots aquests experiments, s'ha donat un pas edanvant en l'explicació dels mecanismes de sensat dels nanofils d'ZnO i els octaedres de In2O3 a diferents temperatures.
En la presente tesis doctoral, se han producido diferentes tipos de nanoestructuras basadas en oxidos metalicos, como por ejemplo nanohilos de ZnO y ocaedros de In2O3, utilizando el método de Deposición Química de Vapor (CVD) a altas temperaturas. Para la detección de dióxido de nitrógeno, se ha descubierto que la respuesta de los nanohilos de ZnO está directamente correlacionada con la cantidad total de defectos presentes en el material. Cuanto mayor es el número de defectos, mayor es la respuesta al dióxido de nitrógeno. Sin embargo, para la detección de etanol, la muestra que contenía un número medio de defectos fue la que dio mejores resultados. Por lo que respecta a los octaedros de In2O3, podemos decir que los octaedros de In2O3 puro son excelentes candidatos para la detección de NO2, ya que poseen una excelente sensibilidad (0.43 ppb-1) a bajas temperaturas (130ºC), mientras que la respuesta a otros gases como H2 es dos órdenes de magnitud inferior en las mismas condiciones. Además, en presencia de humedad, se incrementa la sensibilidad a NO2 y, a la vez, se reduce la sensibilidad a H2, por lo que la selectividad hacia NO2 tambien se ve incrementada. Finalmente, utilizando la espectroscopia DRIFT, se ha analizado el In2O3 expuesto a 1 ppm de NO2 a diferentes temperaturas y se ha descubierto que el mecanismo propuesto para describir el proceso de senado es bastante más complicado que lo que se ha publicado hasta ahora. Como resultado de todos estos experimentos, se ha arrojado luz nueva sobre los mecanismos de sensado de los nanohilos de ZnO y los octahedros de In2O3 a diferentes temperaturas.
In the present doctoral thesis, several metal oxide nanostructures such as ZnO nanowires and In2O3 octahedra via a chemical vapour deposition (CVD) method at high temperatures. For the detection of nitrogen dioxide, it was found that the response of ZnO nanowires was directly correlated to the overall amount of defects of the material. The higher the number of defects is, the higher the response to nitrogen dioxide is. On the other hand, for the detection of ethanol, ZnO nanowires with an intermediate number of defects in which surface defects were dominant led to the best results. Additionally, regarding the In2O3 octahedra, we can say that pure In2O3 octahedra are excellent for detecting NO2 gas with an outstanding sensitivity (0.43 ppb-1) at low temperatures (130ºC), while the response to H2 remains two orders of magnitude lower under the same conditions. In addition, the presence of humidity increases the sensitivity to NO2 and, at the same time, reduces the response to H2, which results in an increased selectivity. Finally, by making use of the DRIFT spectroscopy, we have analyzed In2O3 material towards 1 ppm of NO2 at different temperatures and, it has been found that the mechanism proposed for the gas sensing is far more complicated than previously reported. As a result of these experiments, new light on the sensing mechanism of ZnO and In2O3 material towards NO2 gas at different temperatures has been shed.

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38

Scribbins, Ashley Chandler. "Synthesis and properties of some novel liquid crystalline systems including metallomesogens." Thesis, Nottingham Trent University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389686.

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39

Hasson, Craig. "Preparation and properties of liquid crystalline elastomers with chiral nematic structure." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326186.

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40

Hogan, Sarah Eve. "Investigation of the amorphous and crystalline properties of lactose and raffinose." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268883.

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41

Waigh, Thomas Andrew. "The structure and side-chain liquid-crystalline polymeric properties of starch." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284951.

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42

Wensley, Charles Alexander. "Processing and Properties of Amorphous NiW Reinforced Crystalline Ni Matrix Composites." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/30793.

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Metal Matrix Composites (MMCs) are used as structural materials because of their ability to have a combination of high strength and good ductility. A common problem with MMCs utiliz-ing vastly different materials is the difficulty in forming a strong matrix/reinforcement interface without suffering extensive dissolution, debonding, or chemical reactions between the compo-nents. In this work, a nickel base amorphous particulate reinforced crystalline nickel matrix composite is processed. The reinforcement, an equimolar NiW amorphous powder, was synthe-sized using the mechanical alloying process. The amorphous and crystalline nickel powders were blended in varying volume fractions and then consolidated using hot-isostatic pressing (HIP). This work reveals that the amorphous NiW reinforcement provides strength and hardness to the ductile Ni matrix while simultaneously maintaining a strong interfacial bond due to the similar chemistry of the two components. The strengthening achieved in the composite is attrib-uted to the particulate/matrix boundary strengthening.
Master of Science

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43

Tsung-Wen, Huang, and 黃宗文. "Liquid Crystalline Properties of BisimidazoliumSalts with different anion Liquid Crystalline Properties of BisimidazoliumSalts with different anion Liquid Crystalline Properties of Bisimidazolium Salts with differen anion." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/95040985495612608455.

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碩士
輔仁大學
化學系
93
The aim of this work is to synthesize and investigated liquid crystalline properties of bisimidazolium salts with different anions [(Im18)2Cn][X]2 n = 2, 3, 4, 5, 6, 8, 9, 10 ; X = PF6 and BF4 . The bisimidazolium salts with different anion were prepared by anion metathesis. These [(Im18)2Cn][X]2 salts have a liquid crystalline properties, most of these compounds exhibited SmA mesophase ; a small of these compounds exhibited smectic highly order mesophase. By the PXRD analysis we found that with the increase of n number, there are two kinds of situations of the d-spacing (from solid phase into liquid crystal phase). Liquid crystal behaviors of these compounds were investigated by differential scanning calorimetry, polarized optical microscopy and powder X-ray diffraction.

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44

Hung, Ying Jer, and 黃英哲. "Electrorheological of Liquid Crystalline Polymer Properties." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/52767134547099036718.

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45

Guo, Zhen-Kuan, and 郭真寬. "Synthesis of liquid crystalline polymers and properties." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/60896405940478776305.

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46

TSENG, HSIAO-YI, and 曾效沂. "Synthesis and Properties of Liquid Crystalline Epoxy." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/16213962506794065654.

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碩士
國立臺灣大學
材料科學與工程學研究所
86
The synthesis of two novel liquid crystalline epoxies, one based on Schiff b ase with azomethine linkage : 4,4''-bis(2,3-epoxypropoxy) benzylideneaniline(DG EAM), the other based on biphenyl mesogen : 4,4''-bis(2,3-epoxypropoxy)biphenyl (DGEBP), has been presented. DGEAM shows nematic mesophase while DGEBP with sm ectic phase from the observation of polarized optical microscope. These two li quid crystalline epoxies are cured by sulfanilamide(SAA) under proper curing c onditions and characterized with the use of dynamic mechanical analysis(DMA), thermomechanical analysis(TMA), thermogravimetric analysis(TGA) and X-ray diff raction. Liquid crystalline epoxies, DGEAM and DGEBP, have higher glass transi tion temperature(Tg) and lower thermal expansion coefficient(CTE) compared wit h the conventional DGEBA epoxy. The DGEAM, with the heat stability of the azom ethine linkage, has the lowest speed of degradation. The conventional epoxy,DG EBA, degrades fast due to the Bisphenol A segment. On the basis of X-ray diffr action analysis, the DGEAM-SAA is an isotropic epoxy thermoset. The DGEBP-SAA, on the contrary, is a liquid crystalline epoxy thermoset probably with the pr esvervation of smectic phase inside the network.

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47

Sun, Shih Jien, and 孫時傑. "Synthesis and properties of liquid crystalline polycarbonates." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/28758202312275277094.

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48

JU, LEE YI, and 李宜儒. "Synthesis and Properties of Segmented Liquid Crystalline Polyurethane." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/31913024301319327400.

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碩士
國立成功大學
化學工程學系
88
Abstract A series of mesogenic unit with biphenyl group as mesogen core and alkoxy group as flexible chain, 4,4’-bis(ω-hydroxyalkyloxy)-biphenyls, were synthesized , which included 4,4’-bis(2-hydroxyethoxy) biphenyl (BHEBP), 4,4’-bis(3-hydroxypropenoxy)biphenyl (BHPBP) and 4,4’-bis (6-hydroxyhexoxy) biphenyl (BHPBP) . FTIR , EA and H1-NMR were used to confirm their structures . The thermal behaviour and phase behaviour were characterized by DSC, optical microscopy and WXRD. Studies indicate that mesophase of the three mesogenic unit are all smectic G or smectic H and all trans conformation requires a 50°~60°tilt of the molecules in the smectic layers. Besides, the stability of the mesophase were BHHBP > BHEBP > BHPBP. BHPBP and BHHBP are used as the mesogenic unit in the synthesis of homopolyurethanes and copolyurethanes. Homopolyurethane P3 was observed to exhibit smectic-like phase , however , P6 was observed to exhibit crystalline phase only. All copolyurethanes are hard to recognize if the mesophase do exist by using optical microscopy.

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Chang, Piao-Fu, and 張標富. "Physical Properties of Main-Chain Liquid Crystalline Polyurethanes." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/99726372720964243800.

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碩士
元智大學
化學工程學系
91
In this study, we report physical properties of main-chain liquid crystalline polyurethanes. Thermotropic hard segment type liquid crystalline polyurethanes can be obtained by a step polyaddition reaction from mesogenic diols with diisocyanates. All the thermal decomposition behavior of polyurethanes are about 300℃. It shows that the technical application of polyurethanes is limited. In order to obtain polymers with a high application we became interested in the study of decrease of the hard segment melting points to enhance mesogenic temperature range △TLC (i.e. △TLC =Tm→TN-I). Phase segregation of polyurethanes was investigate by DSC, FTIR and POM. It was found that the temperatures of phase transitions depend on the amount of mesogenic diols substituted for 1,4-BD. They show a higher transition temperature (Tg and Tm) when the polyurethanes have been raised by the increase of the amount of mesogenic diols. The transition temperatures and the temperature ranges of mesophases also changed with the length of alkoxy spacer and the kind of diisocyanate. The longer the spacer length, the lower is the transition temperature. And MDIn shows a higher Td than that of TDIn.

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50

Liao, Chi-Hung, and 廖啟宏. "Single Crystalline Zn2GeO4 Nanowires and Their Optoelectronic Properties." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/29688589495796884825.

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碩士
國立交通大學
材料科學與工程學系所
101
In this work, Zn2GeO4 nanowires (NWs) have been successfully synthesized on Si (100) substrate through carbon thermal reduction and vapor-liquid-solid method. The diameters of the NWs are in the range of 80-150 nm with high aspect ratio (AR>100). The X-ray diffraction (XRD) peaks revealed that the phase is rhombohedral Zn2GeO4. High resolution transmission electron microscopy (HRTEM) indicated that the NWs are perfect single-crystalline with [110] growth direction. Moreover, the atomic resolution high-angle annular dark-field (HAADF) and bright field images of scanning transmission electron microscopy (STEM) can distinguish the different elements of atoms. They further clarified the structure of Zn2GeO4 and the position of elements located. The room temperature photoluminescence spectra of Zn2GeO4 NWs revealed high UV emission and broad blue emission. The UV emission was attributed to the Zinc interstitial, of which the intensity decreased as temperature increasing. Furthermore, we have fabricated the device to measure electrical properties of the single NW. The platinum electrodes of the device were deposited by focus ion beam (FIB). It is remarkable that individual Zn2GeO4 NW device exhibited excellent optoelectronic property with fast switching speed under 254 nm UV illuminations. The result showed that Zn2GeO4 NWs can be served as the building blocks for UV photodetectors. In addition, while exposing Zn2GeO4 NWs, which soaking in methyl orange solution. With short wavelength UV illumination, the methyl orange were degraded. This result showed that Zn2GeO4 NWs can be used in degrading organic pollutants. In conclusion, Zn2GeO4 NWs show highly potential applications in UV photodetectors and degradation of organic pollutants.

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Dissertations / Theses on the topic 'Crystalline properties'

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