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Efeitos de Superfícies de Contorno na Orientação de Cristais Líquidos Liotrópicos; Boundary Surface Effects on the Liotropic Liquid Crystal Orientation

Bechtold, Ivan Helmuth
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/05/2000 PT
Relevância na Pesquisa
66.27%
Para uso em aplicações tecnológicas os cristais líquidos são geralmente confinados em em celas, onde a interação do cristal líquido com a superfície de contorno é de grande importância para o bom desempenho do dispositivo. Os cristais líquidos liotrópicos em particular, possuem propriedades físicas muito mais complexas que os termotrópicos, que não são conhecidas em sua totalidade. Dessa forma, desenvolvemos um estudo com o objetivo de investigar a influência da superfície na configuração de uma amostra de cristal líquido liotrópico. Utilizamos alguns tratamentos de superfície para alterar as condições de contorno e investigar a orientação induzida ao cristal líquido. Esses tratamentos alteram as propriedades físico-químicas das superfícies, tais como o caráter hidrofílico (utilizando lâminas de vidro) e hidrofóbico (utilizando lâminas de vidro recobertas com polímero). Outro tratamento empregado consiste no esfregamento dos substratos ao longo de uma direção preferencial que pode alterar a topografia das superfícies. Variamos a espessura da amostra para comparar os efeitos devido as interações da superfície em relação as interações entre as moléculas no volume. Efetuamos análise de textura da amostra de cristal líquido liotrópico após colocada nas celas fabricadas com os substratos tratados. Através de medidas de transmitância de um feixe de luz polarizada pela amostra...

Dispersão de nanopartículas de látex em um cristal líquido liotrópico; Dispersion of nanoparticles of latex in the lyotropic liquid crystal

Nakamatsu, Sandra
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/09/2008 PT
Relevância na Pesquisa
66.33%
Neste trabalho, estudamos a dinâmica de formação e dispersão de agregados de látex quando inseridos num cristal líquido liotrópico. Esse cristal líquido é um sistema ternário composto de laurato de potássio, cloreto de decilamônia e água; e apresenta fases nemáticas uniaxiais calamítica e discótica (NC e ND, respectivamente) e biaxial (NB). As partículas de látex possuem diâmetro de 100nm e partículas com diferentes tipos de recobrimentos foram testadas. Observamos que nas fases NC e NB há formação de aglomerados de partículas, porém na transição para a fase ND as partículas se dispersam no meio. Verificamos que esse processo de aglomeração e dissociação das partículas está relacionado com a transição de fase NB - ND e foi observado em dois sistemas hospedeiros por resfriamento e por aquecimento. No intervalo de temperatura que corresponde à fase nemática biaxial para o cristal líquido puro, observa-se que há um aumento na dimensão dos aglomerados, que se tornam anemométrico e orientados na direção de orientação do meio. Dois diagramas de fases foram construídos, variando-se a concentração de partículas dispersas no meio, e a composição relativa de surfactantes do sistema hospedeiro. Experimentos de espalhamento de raios X indicam que a distância média entre as micelas que formam o meio hospedeiro não é alterado pela inserção de partículas no cristal líquido e permanece a mesma em todas as fases nemáticas. Foram também realizados estudos de reologia que mostram que a viscosidade do sistema é alterada pela presença das partículas de látex. Os fenômenos observados são interpretados levando-se em conta as flutuações de orientação das micelas nas diferentes fases nemáticas.; In this work...

Thermal tunability of photonic bandgaps in photonic crystal fibers selectively filled with nematic liquid crystal

Franco, Marcos A.R.; Patrício, Paulo S.; Pitarello, Tânia R.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
66.31%
We address the bandgap effect and the thermo-optical response of high-index liquid crystal (LC) infiltrated in photonic crystal fibers (PCF) and in hybrid photonic crystal fibers (HPCF). The PCF and HPCF consist of solid-core microstructured optical fibers with hexagonal lattice of air-holes or holes filled with LC. The HPCF is built from the PCF design by changing its cladding microstructure only in a horizontal central line by including large holes filled with high-index material. The HPCF supports propagating optical modes by two physical effects: the modified total internal reflection (mTIR) and the photonic bandgap (PBG). Nevertheless conventional PCF propagates light by the mTIR effect if holes are filled with low refractive index material or by the bandgap effect if the microstructure of holes is filled with high refractive-index material. The presence of a line of holes with high-index LC determines that low-loss optical propagation only occurs on the bandgap condition. The considered nematic liquid crystal E7 is an anisotropic uniaxial media with large thermo-optic coefficient; consequently temperature changes cause remarkable shifts in the transmission spectrums allowing thermal tunability of the bandgaps. Photonic bandgap guidance and thermally induced changes in the transmission spectrum were numerically investigated by using a computational program based on the beam propagation method. © 2010 SPIE.

Nasal administration of liquid crystal precursor mucoadhesive vehicle as an alternative antiretroviral therapy

Carvalho, Flávia Chiva; Campos, Michel Leandro; Peccinini, Rosângela Gonçalves; Gremião, Maria Palmira Daflon
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 219-227
ENG
Relevância na Pesquisa
66.25%
The purpose of this study was to develop a mucoadhesive stimuli-sensitive drug delivery system for nasal administration of zidovudine (AZT). The system was prepared by formulating a low viscosity precursor of a liquid crystal phase, taking advantage of its lyotropic phase behavior. Flow rheology measurements showed that the formulation composed of PPG-5-CETETH-20, oleic acid and water (55, 30, 15% w/w), denominated P, has Newtonian flow behavior. Polarized light microscopy (PLM) revealed that formulation P is isotropic, whereas its 1:1 (w/w) dilution with artificial nasal mucus (ANM) changed the system to an anisotropic lamellar phase (PD). Oscillatory frequency sweep analysis showed that PD has a high storage modulus (G′) at nasal temperatures. Measurement of the mucoadhesive force against excised porcine nasal mucosa or a mucin disk proved that the transition to the lamellar phase tripled the work of mucoadhesion. Ex vivo permeation studies across porcine nasal mucosa exhibited an 18-fold rise in the permeability of AZT from the formulation. The Weibull mathematical model suggested that the AZT is released by Fickian diffusion mechanisms. Hence, the physicochemical characterization, combined with ex vivo studies, revealed that the PPG-5-CETETH-20...

Liquid crystal mobility and PDLC memory effects

César, Ana Sofia Reboredo
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Dissertação de Mestrado
Publicado em //2011 ENG
Relevância na Pesquisa
66.3%
Dissertation presented at Faculdade de Ciências e Tecnologia of Universidade Nova de Lisboa to obtain the Degree of Master in Chemical and Biochemical Engineering; PDLCs comprising PEGDA or PEGDMA as polymer matrix to support the liquid crystal E7 from Merck, in a ratio 30/70 (w/w) were studied. These were followed by thermal or photochemical polymerization of these mixtures by FTIR, where there was a similar rate of polymerization for both oligomers. Dielectric relaxation spectroscopy for the PDLC with E7 was used, where the polymer matrix was PEGDMA or PEGDA to study the liquid crystal mobility. The glass transition and the nematic-isotropic transition for E7 in both composites were studied, and the temperatures are consistent with those described in the literature for E7 and already observed by differential scanning calorimetry. The mobility of the liquid crystal alone and confined in the polymer matrix was compared, in a range of temperatures near the glass transition temperature (-60ºC to 0ºC). When an electric field is applied dominates the parallel alignment between all liquid crystal microdomains (the PDLC becomes transparent), after the application of an electric field, if it remains transparent, the PDLC have permanent memory effect. When temperature rise above the clear temperature...

Efeitos de superfície nas transições de fases por redução de camadas em filmes de cristal líquido livremente suspensos.; Surface effects in layer-thinning transitions in free-standing liquid crystal films.

Silva, Askery Alexandre Canabarro Barbosa da
Fonte: Universidade Federal de Alagoas; BR; Física geral; Física teórica e computacional; Mecânica estatística; Ótica; Ótica não linear; Proprie; Programa de Pós-Graduação em Física da Matéria Condensada; UFAL Publicador: Universidade Federal de Alagoas; BR; Física geral; Física teórica e computacional; Mecânica estatística; Ótica; Ótica não linear; Proprie; Programa de Pós-Graduação em Física da Matéria Condensada; UFAL
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
66.2%
Liquid crystals exhibit a great variety of phases which differ one from another by their structure and physical properties. Near a phase transition, these mesoscopic phases are very sensitive to the surface interactions showing interfacial phenomena which are extraordinarily variable and interesting. The interaction between boundary surfaces and liquid crystal molecules results in surface layers with properties strongly different from the interior ones. For example, it is observed experimentally the unusual phenomenon of layer thinning upon heating. Above the bulk Smetic A - Isotropic transition temperature, the film is thinned to a low number of layers as the temperature increases. The temperature of these layer thinning transitions are related to the film thickness by means of a simple power-law. The characteristic exponent, μ, measured from experiments using distinct compounds, varies slightly in the range 0.6 < μ < 0.8. In this work, we investigate how surface effects modify the order parameter profiles in the vicinity of the Smectic-A-Isotropic (Sm A - I) transition in freestanding liquid crystal films using an extended mean-field approach which allows to incorporate explicitly the anchoring of the surface layers in the effective potential. We observed the contribution of the surface anchoring to the film stability. We found that there is a characteristic surface anchoring above which the bulk layers are less ordered than the surface ones. We also determine the characteristic exponent which governs the transition temperature dependence with the film thickness. We show that the different values of the exponents are related with the ratio between the size of the central rigid portion of the molecules and the typical layer spacing...

Genetic optimization of modulation characteristics for two twisted nematic liquid crystal spatial light modulators

Kelly, T.L.; Munch, J.
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
Publicado em //1999 EN
Relevância na Pesquisa
66.23%
A single twisted nematic liquid crystal spatial light modulator may suffer from coupled amplitude modulation and a phase modulation capability of less than 2π, although almost all panels can achieve π. Two twisted nematic liquid crystal panels can be combined in an optical system to produce a total phase modulation of at least 2π, and a minimal coupled amplitude modulation. A genetic algorithm is used to optimize the combined modulation characteristics of two liquid crystal panels in a multiplicative architecture. Simulation results and experimental verification are presented which show a substantial reduction in the combined amplitude modulation, and a total phase modulation of 2π.; Thu-Lan Kelly and Jesper Munch

A multi-layered tunable stepped-impedance resonator for liquid crystal characterization

Yaghmaee, P.; Karami Horestani, A.; Bates, B.; Fumeaux, C.
Fonte: IEEE; USA Publicador: IEEE; USA
Tipo: Conference paper
Publicado em //2012 EN
Relevância na Pesquisa
66.23%
The characterization of a tunable band-pass filter based on stepped-impedance resonator (SIR) is presented in this work. The designed filter uses a half-wavelength resonator patch above a multi-layer substrate, with liquid crystal as its central layer, making it continuously tunable at frequencies around S-band. Two liquid crystal samples are considered for three different approaches: lumped-element circuit simulation, full-wave electromagnetic simulations and prototype measurements. The results demonstrate the possibility of using a simple lumped-element circuit simulation for rapid calculation of the performances of liquid crystal devices at microwave frequencies.; Pouria Yaghmaee, Ali K. Horestani, Bevan Bates and Christophe Fumeaux

Interlayer tuning of X-band frequency-selective surface using liquid crystal

Ebrahimi, A.; Yaghmaee, P.; Withayachumnankul, W.; Fumeaux, C.; Al-Sarawi, S.; Abbott, D.
Fonte: IEEE; USA Publicador: IEEE; USA
Tipo: Conference paper
Publicado em //2013 EN
Relevância na Pesquisa
66.25%
In this paper, a new concept of a voltage-controlled tunable frequency-selective surface (FSS) is introduced based on liquid crystal technology. The designed FSS consists of two periodically patterned metallic layers, separated by a thin dielectric substrate. Tunability is achieved by integrating liquid crystal cells within the substrate for each unit cell, producing interlayer capacitors. By applying a bias voltage between the front and back metallic arrays, the anisotropy axis of the liquid crystal molecules can be re-oriented, and thus the effective relative permittivity of the liquid crystals can be modified to cause a frequency shift in transmission response. Electromagnetic simulations predict 5.6% of continuous frequency tuning for this multi-layer FSS.; Amir Ebrahimi, Pouria Yaghmaee, Withawat Withayachumnankul, Christophe Fumeaux, Said Al-Sarawi and Derek Abbott

Reconfigurable tunable microwave devices using liquid crystal.

Yaghmaee, Pouria
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014
Relevância na Pesquisa
66.31%
During the past decades, the applications of communication devices have extended widely, from AM radio receivers initially to newly developed GPS, smart mobile phones, radars, wireless LANs, satellite communications and implantable medical devices. The shortage in the available frequency spectrum for radio communications, the demand for portable wireless devices, and the requirement for more functionality in an even smaller volume, requires the development of new concepts in RF technology. One ideal pathway towards development of such new concepts is reconfiguration. Today, due to the rapid progress in material science and electronic technology, there is great possibility in designing reconfigurable portable wireless devices which are frequency tunable, flexible and consume low energy. In this thesis, the anisotropic properties of liquid crystals in their nematic phase are exploited as a low-voltage (< 35 V) mechanism for designing tunable wireless devices at a low microwave frequency (L to C-band). To demonstrate the possibility of using liquid crystal technology, three different design approaches were pursued: a liquid crystal tunable resonator, a tunable band-pass liquid crystal filter, both at S-band, and liquid crystal tunable frequency selective surfaces operating at C-band. The results from full-wave electromagnetic simulations...

Modellierung und Charakterisierung von integriert-optischen Wellenleitern im Zusammenwirken mit Polymerfilmen und flüssigkristallinen Schichten für die Umweltanalytik; Modelling and characterisation of liquid crystal and polymer films on integrated optical waveguides for the application in environmental sensing

Drapp, Bernd
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
66.24%
In der vorliegenden Arbeit ist das Zusammenwirken von integriert-optischen Wellenleitern mit Polymerfilmen und flüssigkristallinen Schichten unter dem Einfluß von organischen Lösungsmitteln dargestellt und modelliert. Ausgewählte, nematische Flüssigkristalle mit unterschiedlichen Klärpunkten und unterschiedlicher Doppelbrechung werden einer Reihe organischer Lösungsmittel ausgesetzt und die Änderung der Brechungsindizes optisch gemessen. Dabei wird der Zusammenhang zwischen der optischen Anisotropie und der Orientierung der Flüssig-kristallmoleküle ausgenutzt. Integriert optische Mach-Zehnder Interferometer und integriert optische Gitterkoppler dienen als Evaneszentfeldtransducer zur Brechungsindexmessung. Die Daten aus den Flüssigkristallmessungen werden mit Ergebnissen aus Messungen an einem bekannten, isotropen Polymer verglichen. Daraus läßt sich der Einfluß des Analyten auf den Klärpunkt, den Ordnungsgrad und die Dichteänderung im Flüssigkristall charakterisieren. Die Diskussion der experimentellen Ergebnisse wird durch ein mathematisches Modell für die Flüssigkristall / Analyt Wechselwirkung unterstützt. Das Modell beschreibt den experimentell beobachteten Zusammenhang zwischen der Analytkonzentration und dem Brechungsindex des Flüssigkristalls und ermöglicht so eine transducerfreie Darstellung der Ergebnisse. Die Ergebnisse aus der vorliegenden Arbeit zeigen die Möglichkeiten und Grenzen für den Einsatz von Flüssigkristallen in der optischen Sensorik von organischen Lösungsmitteln auf.; The concept of integrated optics originally has been introduced for the use in telecommunication and optical signal processing. At present...

Electro-optical Simulation of a-Si Thin-Film-Transistor Liquid Crystal Display Pixels

Vázquez, Carmen; Sánchez-Pena, José Manuel; Pérez, Isabel; Otón, José M.
Fonte: John Wiley & Sons Publicador: John Wiley & Sons
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em 05/05/2001 ENG
Relevância na Pesquisa
66.17%
An analysis of an amorphous silicon (a-Si) thin-film-transistor liquid-crystal display (TFT-LCD) pixel is presented. The electro-optical model combines the electrical properties of the switching element and the optical performance of a twisted nematic (TN) liquid-crystal cell.

Temperature-Frequency Converter Using a Liquid Crystal Cell as a Sensing Element

Marcos, Carlos; Sánchez-Pena, José Manuel; Torres, Juan C.; Santos, J. I.
Fonte: MDPI AG Publicador: MDPI AG
Tipo: info:eu-repo/semantics/publishedVersion; info:eu-repo/semantics/article
Publicado em /03/2012 ENG
Relevância na Pesquisa
66.23%
A new temperature-frequency converter based on the variation of the dielectric permittivity of the Liquid Crystal (LC) material with temperature has been demonstrated. Unlike other temperature sensors based on liquid crystal processing optical signals for determining the temperature, this work presents a system that is able to sense temperature by using only electrical signals. The variation of the dielectric permittivity with temperature is used to modify the capacitance of a plain capacitor using a LC material as non-ideal dielectric. An electric oscillator with an output frequency depending on variable capacitance made of a twisted-nematic (TN) liquid crystal (LC) cell has been built. The output frequency is related to the temperature of LC cell through the equations associated to the oscillator circuit. The experimental results show excellent temperature sensitivity, with a variation of 0.40% of the initial frequency per degree Celsius in the temperature range from -6 °C to 110 °C.; This work was supported in part by the Comunidad de Madrid (FACTOTEM2-CM, S2009/ESP-1781) and the Spanish Ministry of Science and Technology (TEC2009-13991-C02-01).

Electrooptic Characterization of Tunable Cylindrical Liquid Crystal Lenses

Urruchi, Virginia; Algorri Genaro, J. F.; Sánchez-Pena, José Manuel; Geday, M. A.; Otón, José M.; Bennis, N.
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article; info:eu-repo/semantics/conferenceObject
Publicado em //2012 ENG
Relevância na Pesquisa
66.2%
In this work, one-dimensional arrays of cylindrical adaptive liquid crystal lenses were manufactured and characterized; and test devices were filled with nematic liquid crystal. Comb interdigitated electrodes were designed as a mask pattern for the control electrode on the top glass substrates. A radial graded refractive index along each microsized lens was achieved by fabricating a layer of high resistance sheet deposited as a control electrode. These tunable lenses were switched by applying amplitude and frequency optimized waveforms on the control electrode. Phase profiles generated by the radial electric field distribution on each lens were measured by a convectional interferometric technique.; This work was supported in part by the Ministerio de Ciencia e Innovación of Spain (grant no.TEC2009-13991-C02-01) and Comunidad de Madrid (grant no. S2009/ESP-1781).; Special Issue: The 11th European Conference on Liquid Crystals (ECLC 2011). Maribor, Slovenia, February 6-11 , 2011

Electrical Modeling of Tristate Antiferroelectric Liquid Crystal Devices

Torres, J. C.; Pérez, Isabel; Urruchi, Virginia; Sánchez-Pena, José Manuel; Marcos, Carlos
Fonte: SPIE. The International Society For Optical Engineering Publicador: SPIE. The International Society For Optical Engineering
Tipo: info:eu-repo/semantics/publishedVersion; info:eu-repo/semantics/article; info:eu-repo/semantics/conferenceObject
Publicado em /06/2011 ENG
Relevância na Pesquisa
66.17%
A new electrical equivalent circuit (EEC) has been proposed to model antiferroelectric liquid crystal devices. This circuit includes a constant phase element to take into account the ferroelectric part of the dielectric response in these devices. Electrical characterization of samples has been carried out using a specific experimental protocol based on impedance spectroscopy. The parameters of waveforms used in impedance measurements have been optimized. The procedure to obtain the components of the EEC has also been explained. Finally, the EEC has been validated by comparing experimental and simulated impedance results. A reasonable agreement between both of them has been obtained in a wide frequency range for all selection voltages; Ciencia e Innovación of Spain (Grant No. TEC2009–13991-C02–01) and Comunidad de Madrid (Grant No. S2009/ESP-1781).; Proocedings of: 3rd International Workshop on Liquid Crystal for Photonics (LCP2010). Elche (Alicante), Spain. September 8-10, 2010; Copyright 2011 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes...

Note: Series and parallel tunable resonators based on a nematic liquid crystal cell as variable capacitance

Torres, J.C.; Marcos, Carlos; Sánchez-Pena, José Manuel; Pérez, Isabel; Urruchi, Virginia
Fonte: AIP Publishing Publicador: AIP Publishing
Tipo: info:eu-repo/semantics/publishedVersion; info:eu-repo/semantics/article
Publicado em /08/2012 ENG
Relevância na Pesquisa
66.17%
In this work, tunable series and parallel resonators based on a nematic liquid crystal cell as variable capacitance are proposed and characterized. Tunable resonance frequencies in the range of kHz have been obtained for the combination of the inductance and the liquid crystal cell (capacitance) used in the proposed circuits. Tuning range in frequency obtained is around an octave.; This work was supported in part by the Spanish Ministry of Science and Technology (TEC2009- 13991-C02-01) and the Comunidad de Madrid (FACTOTEM2-CM, REF.S2009/ESP- 1781).; Copyright 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Review of Scientific Instruments (2012), 83 (8). and may be found at http://dx.doi.org/10.1063/1.4738645

Adaptive micro-optical phase modulators based on liquid crystal technology

Algorri Genaro, José Francisco
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
66.39%
This thesis began with the project “Advanced Devices of Liquid Crystal and Electroluminescent Organic Diodes. Hybrid Applications for 3D Vision” funded by the Spanish government. The goal of this project was the development of optical devices to achieve 3D vision in portable devices without glasses or external elements. In order to achieve the goals of this project, solutions based on liquid crystal are considered. Specifically, adaptive micro-optical phase modulators based on liquid crystal technology are researched in depth. The gradient of the refractive index varies spatially the phase delay experienced by an impinging wavefront of a light beam. By using this effect, any refractive optical element may be reproduced with the proper voltage gradient applied to the sample. This is the main operating principle of the micro-optical phase modulators proposed in this thesis. As original contribution of this thesis, a novel algorithm to solve the position of a nematic liquid crystal molecular director is proposed. Once the liquid crystal is completely characterized, the developing of a specific model to know the electro-optic response of the micro-optical phase modulators is also relevant. Another original contribution is a novel equivalent electric circuit for modeling liquid crystal microlenses. An interesting feature of the model is that it provides an analytical solution for microlenses with modal and hole-patterned electrode schemes...

Liquid crystal spatial light modulators as computer controlled optical elements / (Marie-Therese) Thu-Lan Kelly.

Kelly, Thu-Lan
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 115758 bytes; application/pdf
Publicado em //1997 EN
Relevância na Pesquisa
66.17%
This thesis investigated the suitability of liquid crystal spatial light modulators as versatile computer controlled optical elements. The modulation characteristics were determined empirically and experimentally, and their performance as phase modulators tested in the two diverse applications of computer generated holography and phase aberration correction. Commercial liquid crystal panels from a video projector were used, chosen because of low cost, high resolution, computer controlled input, reconfigurability and ready availability. The panels were found to be more suited to amplitude than to phase modulation. Results show that the devices are versatile enough to be adapted to the two very different applications.; Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1998; Copies of author's previously published articles inserted.; Bibliography: p. 119-129.; xvi, 129, [58] p. : ill. ; 30 cm.; Title page, contents and abstract only. The complete thesis in print form is available from the University Library.

A COMBINED DIRECTED METALATION CROSS-COUPLING ROUTE TO A NEW SMECTIC LIQUID CRYSTAL WITH A PHENANTHRENE CORE

GAN, WEI
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 5770821 bytes; application/pdf
EN; EN
Relevância na Pesquisa
66.25%
A series of phenanthrene and oxidized phenanthrene derivatives with typical substitution patterns, 1.31, 1.32, 2.30a-f, 3.1a,b and (-)-4.1 have been synthesized as liquid crystal cores by a combined Directed ortho Metalation (DoM), cross coupling and Directed Remote Metalation (DreM) strategy. The synthetic methodology employed allowed variation of the tail and core structures, for the preparation of a new smectic liquid crystal compound (1.32), a homologous series of 9,10-dihydrophenanthrene-9,10-diones (2.30a-f), a diastereomeric trans-9,10-dihydrophenanthrene-9,10-diol (1.31), two enantiomeric 9,10-dihydrophenanthrene-9,10-diones (R)-3.1a-b) and an enantiomeric 9,10-dihydro-9,10-dimethylphenanthrene-9,10-diol ((-)-4.1). Polarized microscopic and differential scanning calorimetric measurements suggest that 1.31 forms a large range of SmC phase, ca. 100 ºC, followed by a small range of nematic phase, ca. 10 ºC; the 2.30a-f series show similar mesogenic properties, but with the extension of the length of a side chain from six carbons to eleven carbons, the nematic phase has disappeared (in the cases of 2.30a-c). Although (R)-3.1a-b and (-)-4.1 are not liquid crystals, they show ferroelectric induction by doping, in the amount of ca. 5 mol%...

Synthesis and Characterization of Siloxane-terminated Liquid Crystals and Photochromic Fulgide Dopants for Liquid Crystal Photonics Applications

Li, LI
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 8193457 bytes; application/pdf
EN; EN
Relevância na Pesquisa
66.32%
The goal of this thesis is to design both liquid crystal hosts and photochromic dopants terminated with short siloxane oligomers in order to produce homogeneous liquid crystal mixtures containing a photochromic component for liquid crystal photoswitches. Some of the liquid crystals terminated with short siloxane oligomers were also found to form 'de Vries'-type SmA phases, which minimize the formation of chevrons and zigzag defects that severely degrade the quality of electro-optic devices. In the first part of the thesis, siloxane-terminated phenylpyrimidine liquid crystals were synthesized and characterized. They form SmC phases and, in some cases, SmA phases. Addition of a terminal halogen substituent on the alkoxy side-chain broadens the SmA temperature range. It was shown that combining a structural element that promotes the formation of a SmC phase with one that promotes the formation of a SmA phase in a mesogen with a 2-phenylpyrimidine core results in a maximum layer contraction of 1.6% for 2-(4-(11-(1,1,1,3,3,5,5-heptamethyltrisiloxanyl)undecyloxy)phenyl)-5-(1-chlorooctyloxy)pyrimidine (33a), which may be considered a ‘de Vries’ material. As an extension of the result obtained in the first project, siloxane-terminated biphenyl benzoate and phenyl benzoate liquid crystals were synthesized and their phase behavior studied. They form SmC phases and...