Dissertations / Theses on the topic 'Liquid-liquid crystal phase separation'
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Wang, Shujun. "Liquid-liquid phase separation in an isorefractive polyethylene blend monitored by crystallization kinetics and crystal-decorated phase morphologies." Akron, OH : University of Akron, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1226680911.
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Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Science, 2008."December, 2008." Title from electronic dissertation title page (viewed 12/29/2008) Advisor, Stephen Z. D. Cheng; Committee members, Alexei Sokolov, Darrell H. Reneker, Gustavo A. Carri, Thein Kyu; Department Chair, Ali Dhinojwala; Dean of the College, Stephen Z. D. Cheng; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Wang, Shujun. "Liquid-Liquid Phase Separation in an Isorefractive Polethylene Blend Monitored by Crystallization Kinetics and Crystal-Decorated Phase Morphologies." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1226680911.
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JUSTICE, RYAN SCOTT. "INTERFACE MORPHOLOGY AND PHASE SEPARATION IN POLYMER DISPERSED LIQUID CRYSTAL (PDLC) COMPOSITES." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1163783056.
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Colas, Clémentine. "Bio-inspired synthetic crystals." Thesis, université Paris-Saclay, 2022. http://www.theses.fr/2022UPASF044.
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Les biominéraux calcaires présentent une grande variété de formes et de fonctions biologiques, mais également un certain nombre de traits structuraux communs. En particulier, ils apparaissent, dans leur grande majorité, comme formés d'un assemblage de nanoparticules cristallines sphéroïdales, tout en ayant des propriétés cristallines voisines de celles d'un monocristal. La compacité de cette nanostructure suggère l'existence d'un transitoire liquide précédant la formation d'un état amorphe, quant à lui démontré dans un certain nombre de cas. Le chemin de cristallisation, qui mettrait ainsi en jeu des états intermédiaires typiques des processus de cristallisation dits non-classiques, n'est pas entièrement établi à ce jour. En particulier, l'existence d'une phase liquide enrichie en ions reste complexe à démontrer in vivo. Afin d'évaluer la pertinence d'une telle hypothèse, une approche basée sur un modèle synthétique incluant une phase liquide dense a été utilisée. Des films de carbonate de calcium amorphes d'épaisseur sub-micronique ont été produits par diffusion de CO₂ gazeux dans une solution calcique en présence de polyelectrolyte anionique. Le mécanisme de formation des films, associant le développement d'un motif 2D par séparation de phase liquide-liquide et l'agrégation irréversible de nanoparticules amorphes formées en solution, a été démontré. Les films amorphes ont été cristallisés par chauffage, exposition à une humidité relative contrôlée, ou vieillissement dans le milieu réactionnel. La caractérisation de ces cristaux 2D, notamment par ptychographie de Bragg, a permis de décrire les mécanismes de transition amorphe-cristal et préciser les propriétés cristallines pour chaque condition de cristallisation. Certains cristaux présentent des propriétés très semblables aux cristaux biogéniques, appuyant ainsi l'hypothèse d'un intermédiaire liquide dans la biominéralisation calcaireCalcareous biominerals present a great variety of forms and biological functions, but also a number of common structural features. In particular, they appear, in their great majority, to be formed by an assembly of spheroidal crystalline nanoparticles, while having crystalline properties close to those of a single crystal. The compactness of this nanostructure suggests the existence of a liquid transient prior to the formation of an amorphous state, which has been evidenced in a number of cases. The crystallisation pathway, which would involve intermediate states typical of so-called non-classical crystallisation processes, is not yet fully established. In particular, the existence of an ion-enriched liquid phase remains complex to demonstrate in vivo. In order to assess the relevance of such a hypothesis, an approach based on a synthetic model including a dense liquid phase was used. Amorphous calcium carbonate films of sub-micron thickness were produced by CO₂ gas diffusion in a calcium solution in the presence of anionic polyelectrolyte. The mechanism of film formation, combining the development of a 2D pattern by liquid-liquid phase separation and the irreversible aggregation of amorphous nanoparticles formed in solution, was demonstrated. The amorphous films were crystallized by heating, exposure to controlled relative humidity, or aging in the reaction medium. The characterization of these 2D crystals, in particular by Bragg ptychography, has made it possible to describe the amorphous-crystal transition mechanisms and to specify the crystalline properties for each crystallization condition. Some crystals show properties very similar to biogenic crystals, thus supporting the hypothesis of a liquid intermediate in calcareous biomineralization
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DI, LEO SIMONE. "SELECTIVE ASSEMBLY, PHASE TRANSITIONS AND MOLECULAR KINETICS OF DNA OLIGOMERS." Doctoral thesis, Università degli Studi di Milano, 2022. http://hdl.handle.net/2434/923222.
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In the last few years it has been shown that the spontaneous self-assembly process of short DNA and RNA duplexes into liquid crystal ordering is a likely potential route that led to the formation of first nucleic acids able to support biological activities. In particular, it has been experimentally demonstrated that liquid crystal domains behave as suitable micro-reactors to trigger polymerization between the stacked and not initially chemically linked short nucleic acids. Even paired mononucleotides at high enough concentration exhibit liquid crystal ordering, unveiling the crucial role of Watson-Crick selectivity and stacking attractive interactions among base pairs. In such a possible prebiotic context, DNA sequences with both random nucleobases sequence and length are likely to be formed. Surprisingly, it has been shown that even random DNA sequence of fixed length can support liquid crystal ordering at high concentration.
The aim of this PhD thesis is to extend the knowledge of DNA liquid crystals self-assembly in the following four directions.
First, I explored the selectivity of interaction in nucleic acids solutions of random-sequence DNA oligomers of different length L. The combination of experimental results and a suitable developed theoretical model revealed a not negligible percentage of perfect duplexes.
Second, I investigated the process that leads to the onset of the nematic liquid crystal phase in aqueous solutions of DNA duplexes. The combination of static light scattering experiments and computer simulations made possible the study of both aggregation and local ordering of DNA duplexes in the isotropic phase, where no positional order is developed, and in proximity of the isotropic-nematic phase boundary. This study gives an insight of the role on the development of local orientational order among DNA duplexes both far and in proximity of the isotropic-nematic phase boundary.
Third, I studied the diffusion of short DNA duplexes with attractive and repulsive interactions in the isotropic phase as a function of temperature. I found that the temperature dependence of diffusion coefficients reflects via an Arrhenius law the interduplex attractive interactions, whereas diffusion of repulsive duplexes is partially well described in terms of repulsive hard spheres.
Fourth, I investigated phase diagrams of mixtures of DNA single strands and duplexes with various polycations that show liquid-liquid phase separations. This phenomena leads to the onset of a concentrated but still liquid phase of polyelectrolytes, called coacervate, in a bulk phase where polyelectrolytes are diluted. The most surprising result I found, it is the insurgence of liquid crystals in coacervates with 12 nucleobases long random DNA oligomers and polylysine at different ionic strengths.
I believe that this PhD thesis adds important pieces to the self-assembly of nucleic acids puzzle, and in particular it shows how randomness of nucleic acids is not an impasse to both hybridization of defectless duplexes and liquid crystal ordering.
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Khanal, Kiran. "Liquid-Crystalline Ordering in Semiflexible Polymer Melts and Blends: A Monte Carlo Simulation Study." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1373901748.
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Nilsson, Peter. "Interaction between Crosslinked Polyelectrolyte Gels and Oppositely Charged Surfactants." Doctoral thesis, Uppsala University, Department of Pharmacy, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8216.
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The interactions between anionic, crosslinked gels and cationic surfactants have been investigated. When exposed to oppositely charged surfactant, the gel collapses into a dense complex of polyion and micelles. During deswelling, the gel phase separates into a micelle-rich, collapsed surface phase, and a swollen, micelle-free core, both still part of the same network. As more surfactant is absorbed, the surface phase grows at the expense of the core, until the entire gel has collapsed. Polyacrylate (PA) gels with dodecyl- (C12TAB), and cetyltrimethylammonium bromide (C16TAB), as well as hyaluronate gels with cetylpyridinium chloride, have been studied.
Kinetic experiments have been performed on macro- as well as microgels, using micromanipulator assisted light microscopy for the latter. A surfactant diffusion controlled deswelling model has been employed to describe the deswelling. The deswelling kinetics of PA microgels have been shown to be controlled by surfactant diffusion through the stagnant layer surrounding the gel, as the surface phase is relatively thin for the major part of the deswelling. For macroscopic PA gels the surface phase is thicker, and the kinetics with C12TAB were therefore also influenced by diffusion through the surface phase, while for C16TAB they were dominated by it.
Relevant parameters have also been determined using equilibrium experiments. An irregular, balloon-forming deswelling pattern, mainly found for macrogels, as well as unexpectedly long lag times and slow deswelling for microgels, are reported and discussed.
The microstructure of fully collapsed PA/C12TAB complexes has been studied using small-angle X-ray scattering. A cubic Pm3n structure was found at low salt concentration, which melted into a disordered micellar phase as the salt concentration was increased. Further increasing the salt concentration dissolved the micelles, resulting in no ordering.
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You, Yuan. "Liquid-liquid phase separation in atmospherically relevant particles." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50466.
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Aerosol particles containing both organic material and inorganic salts are abundant in the atmosphere. These particles may undergo phase transitions when the relative humidity fluctuates between high and low values in the atmosphere. This dissertation focuses on liquid-liquid phase separation in atmospherically relevant mixed organic-inorganic salt particles. Liquid-liquid phase separation has potentially important implications in chemical and physical processes in the atmosphere. A humidity and temperature controlled flow cell coupled to either an optical, fluorescence, or Raman microscope was used to study the occurrence of liquid-liquid phase separation and the phase separation relative humidity (SRH) of particles containing atmospherically relevant organic species mixed with inorganic salts. Organic species in the particles studied include single organic species, such as carboxylic acids, alcohols, and oxidized aromatic compounds, as well as complex laboratory-produced secondary organic material. Material directly collected from the atmospheric environment was also studied. In this dissertation, the effects of oxygen-to-carbon elemental ratio (O:C) of the organic species, salt types, molecular weight of the organic species, and temperature on the occurrence of liquid-liquid phase separation and SRH were studies. The oxygenic-to-carbon elemental ratio was a useful parameter for predicting liquid-liquid phase separation and SRH. Liquid-liquid phase separation did not depend strongly on the molecular weight of the organic species or temperature. The correlation between SRH and O:C in particles containing organic species mixed with different salts were qualitatively similar. Results of this research will help improve the understanding of liquid-liquid phase separation in the atmospheric aerosols, and may, in turn, improve simulations and predictions of atmospheric chemistry and climate. Supplementary materials: http://hdl.handle.net/2429/50970Science, Faculty of
Chemistry, Department of
Graduate
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Vliet, Roland Edward van. "Polymer-solvent liquid-liquid phase separation thermodynamics, simulations & applications /." [Amsterdam : Amsterdam : Instituut voor Technische Scheikunde, Universiteit van Amsterdam] ; Universiteit van Amsterdam [Host], 2002. http://dare.uva.nl/document/64948.
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Mercer, Carolyn Regan. "Liquid crystal point diffraction interferometer." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187127.
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A new instrument, the liquid crystal point diffraction interferometer (LCPDI), has been developed for the measurement of phase objects. This instrument maintains the compact, robust design of Linnik's point diffiaction interferometer (PDI) and adds to it phase stepping capability for quantitative interferogram analysis. The result is a compact, simple to align, environmentally insensitive interferometer capable of accurately measuring optical wavefronts with very high data density and with automated data reduction. This dissertation describes the theory of both the PDI and liquid crystal phase control. The design considerations for the LCPDI are presented, including manufacturing considerations. The operation and performance of the LCPDI are discussed, including sections regarding alignment, calibration, and amplitude modulation effects. The LCPDI is then demonstrated using two phase objects: a defocus difference wavefront, and a temperature distribution across a heated chamber filled with silicone oil. The measured results are compared to theoretical or independently measured results and show excellent agreement. A computer simulation of the LCPDI was performed to verify the source of observed periodic phase measurement error. The error stems from intensity variations caused by dye molecules rotating within the liquid crystal layer. Methods are discussed for reducing this error. Algorithms are presented which reduce this error; they are also useful for any phase-stepping interferometer that has unwanted intensity fluctuations, such as those caused by unregulated lasers. It is expected that this instrument will have application in the fluid sciences as a diagnostic tool, particularly in space based applications where autonomy, robustness, and compactness are desirable qualities. It should also be useful for the testing of optical elements, provided a master is available for comparison.
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Jordan, Alexander Thomas. "Liquid phase plasma technology for inkjet separation." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47543.
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Currently most deinking technologies are dependent upon flotation and dissolved air flotation
(DAF) technology in order to separate inkjet ink from fiber and water. Much of this
technology is based on ink that is extremely hydrophobic. This made flotation and DAF
very easy to use because the ink in the water would very easily move with the air in flotation
and be brought to the surface, after which the ink can be skimmed and the pulp can
be used.
Now that small scale printing has become the norm, there has been a move to high
quality, small scale printing. This involves the use of a hydrophilic ink. Hydrophilic ink
cannot be easily separated from water and fiber the same way the hydrophobic ink can be.
With low concentrations of hydrophilic ink in the process water stream, it can be absorbed
into the process but as the hydrophilic ink concentration rises alternative methods will be
needed in order to separate inkjet ink from water.
One solution is to find a method to effectively increase ink particle size. This will
enable the ink particles to be filtered or to have an increase ecacy of removal during
flotation. In this thesis, one solution is discussed about how electric field and electric
plasma technologies can be used to increase particle size and help purify process water in
recycle mills.
This plasma treatment can very effectively bring ink particles together so that they may
be separated by another method. There are two methods by which this may take place. One
is polymerization and the other is electro-coagulation. These processes can work side by
side to bring ink particles together.
This plasma treatment process creates free radicals by stripping off hydrogen atoms
from surrounding organic matter. These free radicals then react with the high alkene bond
content within the ink to create a very large covalently bonded molecule. This is the new
mechanism that is being investigated in this thesis. The other action that is taking place is electro-coagulation.
Plasma treated ink can be filtered out using a cellulose acetate or cellulose nitrate membrane
or they can be filtered using paper or fiber glass filters as well. The extent at which
these can be filtered out is dependent on the size of the pores of the filter. In this study, it
was shown that the plasma treatment was able to clean water with a fairly small amount
of energy. It was also found that treatment time and concentration had very little eect on
the outcome of the treatment ecacy. One factor that did have an effect was the pH. At
very high pH values the process became noticeably less eective. The high pH essentially
eliminated the electro-coagulation aspect of the treatment process and also hurt the polymerization
aspect as well because of lower amount of hydrogen atoms available for the
plasma to create free radicals.
A model of the process was used to try to give the reader an idea of the ecacy that the
process would have in an industrial scale process. The model assumes that two types of ink
particles exist. One is ink that has a radical and another in which the ink does not have a
radical. The model also assumes that if ink is at all polymerized, ink is filtered out with the
0.8 micron filter. The model assumes three reactions; initialization, propagation and partial
termination. The partial termination is a result from the general chemical structure of ink.
Ink has many double bonds in its general structure which makes termination very unlikely
to occur, so the model assumes that on average when two radials interact that only one is
eliminated. This model is only supposed to give the reader an idea of the ecacy of the
process. The numbers provided in the model will change very significantly in a different
system.
The evidence behind polymerization aspect of the process comes from two main sources.
One is the small molecule analysis from methanol after being exposed to the plasma and the
other from the plasma being exposed to allyl alcohol. The small molecule analysis shows
that the process generates free radicals on organic molecules. Methanol was exposed to
the plasma and then the resulting GC/MS analysis showed that 1,2-ethanediol was present, this showed that the electric discharge process was able to create free radicals on organic
molecules in the liquid phase.
Using a similar process the plasma discharge process was exposed to a mixture of allyl
alcohol, water and propanol and water in two separate experiments. The difference between
these two molecules is an alkene bond that is between the carbon two and carbon three
atoms. The particle size of both samples was then analyzed and it was shown that the
solution with allyl alcohol had an average particle size about an order of magnitude larger
than the solution with propanol in it.
Because of all the evidence discussed here and in the rest of the thesis we believe that
the plasma treatment of ink has both polymerization and electro-coagulation aspect. This
process could also be a potential solution to the water soluble ink problem that will soon
face the recycling industry.
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Dowling, P. D. "Optimisation of electrically augmented liquid phase separation." Thesis, University of Bradford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374913.
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Li, Yan. "High-efficiency Blue Phase Liquid Crystal Displays." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5399.
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Blue phase liquid crystals (BPLCs) have a delicate lattice structure existing between chiral nematic and isotropic phases, with a stable temperature range of about 2 K. But due to short coherent length, these self-assembled nano-structured BPLCs have a fast response time. In the past three decades, the application of BPLC has been rather limited because of its narrow temperature range. In 2002, Kikuchi et al. developed a polymer stabilization method to extend the blue-phase temperature range to more than 60 K. This opens a new gateway for display and photonic applications. In this dissertation, I investigate the material properties of polymer-stabilized BPLCs. According the Gerber's model, the Kerr constant of a BPLC is linearly proportional to the dielectric anisotropy of the LC host. Therefore, in the frequency domain, the relaxation of the Kerr constant follows the same trend as the dielectric relaxation of the host LC. I have carried out experiments to validate the theoretical predictions, and proposed a model called extended Cole-Cole model to describe the relaxation of the Kerr constant. On the other hand, because of the linear relationship, the Kerr constant should have the same sign as the dielectric anisotropy of the LC host; that is, a positive or negative Kerr constant results from positive or negative host LCs, respectively. BPLCs with a positive Kerr constant have been studied extensively, but there has been no study on negative polymer-stabilized BPLCs. Therefore, I have prepared a BPLC mixture using a negative dielectric anisotropy LC host and investigated its electro-optic properties. I have demonstrated that indeed the induced birefringence and Kerr constant are of negative sign. Due to the fast response time of BPLCs, color sequential display is made possible without color breakup. By removing the spatial color filters, the optical efficiency and resolution density are both tripled. With other advantages such as alignment free and wide viewing angle, polymer-stabilized BPLC is emerging as a promising candidate for next-generation displays. However, the optical efficiency of the BPLC cell is relatively low and the operating voltage is quite high using conventional in-plane-switching electrodes. I have proposed several device structures for improving the optical efficiency of transmissive BPLC cells. Significant improvement in transmittance is achieved by using enhanced protrusion electrodes, and a 100% transmittance is achievable using complementary enhanced protrusion electrode structure. For a conventional transmissive blue phase LCD, although it has superb performances indoor, when exposed to strong sunlight the displayed images could be washed out, leading to a degraded contrast ratio and readability. To overcome the sunlight readability problem, a common approach is to adaptively boost the backlight intensity, but the tradeoff is in the increased power consumption. Here, I have proposed a transflective blue phase LCD where the backlight is turned on in dark surroundings while ambient light is used to illuminate the displayed images in bright surroundings. Therefore, a good contrast ratio is preserved even for a strong ambient. I have proposed two transflective blue phase LCD structures, both of which have single cell gap, single gamma driving, reasonably wide view angle, low power consumption, and high optical efficiency. Among all the 3D technologies, integral imaging is an attractive approach due to its high efficiency and real image depth. However, the optimum observation distance should be adjusted as the displayed image depth changes. This requires a fast focal length change of an adaptive lens array. BPLC adaptive lenses are a good candidate because of their intrinsic fast response time. I have proposed several BPLC lens structures which are polarization independent and exhibit a parabolic phase profile in addition to fast response time. To meet the low power consumption requirement set by Energy Star, high optical efficiency is among the top lists of next-generation LCDs. In this dissertation, I have demonstrated some new device structures for improving the optical efficiency of a polymer-stabilized BPLC transmissive display and proposed sunlight readable transflective blue-phase LCDs by utilizing ambient light to reduce the power consumption. Moreover, we have proposed several blue-phase LC adaptive lenses for high efficiency 3D displays.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
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Rao, Linghui. "Low Voltage Blue Phase Liquid Crystal Displays." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5448.
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From cell phones, laptops, desktops, TVs, to projectors, high reliability LCDs have become indispensable in our daily life. Tremendous progress in liquid crystal displays (LCDs) has been made after decades of extensive research and development in materials, device configurations and manufacturing technology. Nowadays, the most critical issue on viewing angle has been solved using multidomain structures and optical film compensation. Slow response time has been improved to 2-5 ms with low viscosity LC material, overdrive and undershoot voltage, and thin cell gap approach. Moving image blur has been significantly reduced by impulse driving and frame insertion. Contrast ratio in excess of one million-to-1 has been achieved through local dimming of the segmented LED backlight. The color gamut would exceed 100% of the NTSC (National Television System Committee), if RGB LEDs are used. Besides these technological advances, the cost has been reduced dramatically by investing in advanced manufacturing technologies. Polymer-stabilized blue phase liquid crystal displays (BPLCDs) based on Kerr effect is emerging as a potential next-generation display technology. In comparison to conventional nematic devices, the polymer-stabilized BPLCDs exhibit following attractive features: (1) submillisecond response time, (2) no need for molecular alignment layers, (3) optically isotropic dark state when sandwiched between crossed polarizers, and (4) transmittance is insensitive to cell gap when the in-plane electrodes are employed. However, aside from these great potentials, there are still some tough technical issues remain to be addressed. The major challenges are: 1) the operating voltage is still too high (~50 Volts vs. 5 Volts for conventional nematic LCDs), and the transmittance is relatively low (~65% vs. 85% for nematic LCDs), 2) the hysteresis effect and residual birefringence effect are still noticeable, 3) the mesogenic temperature range is still not wide enough for practical applications (?40 oC to 80 oC), and 4) the ionic impurities in these polymer-stabilized nano-structured LC composites could degrade the voltage holding ratio, which causes image sticking. In this dissertation, the BPLC materials are studied and the new BPLC device structures are designed to optimize display performances. From material aspect, the electro-optical properties of blue phase liquid crystals are studied based on Kerr effect. Temperature effects on polymer-stabilized blue phase or optically isotropic liquid crystal displays are investigated through the measurement of voltage dependent transmittance under different temperatures. The physical models for the temperature dependency of Kerr constant, induced birefringence and response time in BPLCs are first proposed and experimentally validated. In addition, we have demonstrated a polymer-stabilized BPLC mixture with a large Kerr constant K~13.7 nm/V2 at 20 oC at 633 nm. These models would set useful guidelines for optimizing material performances. From devices side, the basic operation principle of blue phase LCD is introduced. A numerical model is developed to simulate the electro-optic properties of blue phase LCDs based on in-plane-switching (IPS) structure. Detailed electrode dimension effect, distribution of induced birefringence, cell gap effect, correlation between operation voltage and Kerr constant, and wavelength dispersion are investigated. Viewing angle is another important parameter. We have optimized the device configurations according to the device physics studied. With proper new device designs, the operating voltage is decreased dramatically from around 50 Volts to below 10 Volts with a reasonably high transmittance (~70%) which enables the BPLCDs to be addressed by amorphous silicon thin-film transistors (TFTs). Moreover, weak wavelength dispersion, samll color shift, and low hysteresis BPLCDs are achieved after their root causes being unveiled. Optimization of device configurations plays a critical role to the widespread applications of BPLCDs. In addition to displays, blue phase liquid crystals can also be used for photonic applications, such as light modulator, phase grating, adaptive lens and photonic crystals. We will introduce the application of blue phase liquid crystal as a modulator to realize a viewing angle controllable display. The viewing angle can be tuned continuously and precisely with a fast response time. The detailed design and performance are also presented in this dissertation.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
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Fine, Bernard Martin. "Light scattering by aqueous protein solutions that exhibit liquid-liquid phase separation." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28079.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Whitaker College of Health Sciences and Technology, 1994.Includes bibliographical references (leaves 177-184).
by Bernard Martin Fine.
Ph.D.
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Poggemann, Hanna-Friederike. "Investigation on liquid liquid phase separation of lysozyme by dynamic light scattering." Thesis, Stockholms universitet, Fysikum, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-193168.
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The liquid-liquid phase separation (LLPS) of biomolecules is a phenomenon which received a lot of attention in the last years because it is not only related to theformation of membraneless organelles but also to neurodegenerative diseases. Lysozyme is a globular protein that undergoes LLPS in a buffer salt system andfor that it is well investigated with several techniques like microscopy, dynamic lightscattering (DLS) or small-angle X-ray scattering. In this work we investigate the effect of temperature, solvent and sample con-centration on the diffusion coefficient, the hydrodynamic radius and the viscosity oflysozyme using a DLS setup. Furthermore, the influence of these parameters on thecluster formation is addressed. Finally, we investigate the question if the LLPS oflysozyme in a buffer environment effects the formation of dynamic clusters.
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Lin, Yi-Hsin. "POLARIZATION-INDEPENDENT LIQUID CRYSTAL DEVICES." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4199.
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Liquid crystal (LC) devices can be operated as amplitude modulators and phase modulators. LC amplitude modulation is commonly used in liquid crystal display (LCD) while phase-only modulation is useful for laser beam steering, tunable grating, prism, lens, and other photonic devices. Most LC devices are polarization dependent and require at least one polarizer. As a result, the optical efficiency is low. To enhance display brightness, a power hungry backlight has to be used leading to a high power consumption and short battery life. In a LC phase modulator, the polarization dependent property complicates the laser beam steering system. It is highly desirable to develop new operating mechanisms that are independent of the incident light polarization. In this dissertation, we have developed eight polarization-independent liquid crystal operation principles: three of them are aimed for displays and the other five are for phase modulators. For amplitude modulations, a new polymer-dispersed liquid crystal (PDLC) and two new dye-doped LC gels are polarizer-free by combining light scattering with dye-absorption effects. In phase modulation, we explore five device concepts: PDLC and Polymer-Stabilized Cholesteric Texture (PSCT), homeotropic LC gels, thin polymer film separated double-layered structure, and double-layered LC gels. In the low voltage regime, both PDLC and PSCT have a strong light scattering. However, as the voltage exceeds a certain level, the phase modulation is scattering-free and is independent of polarization. The homeotropic LC gels do not require any biased voltage and the response time is still fast. Although the remaining phase in these devices is small, they are still useful for micro-photonic device applications. To increase the phase change, thin polymer film separated double-layered structure is a solution. The orthogonal arrangement of top and bottom LC directors results in polarization independence. However, the response time is slow. Similarly, double-layered LC gels are not only polarization independent but also fast response due to the established polymer network.Ph.D.
Optics and Photonics
Optics
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Lifsey, Karen Marie. "Liquid crystal polymers : a unique class of separation media." Thesis, University of East Anglia, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365163.
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Hemström, Petrus. "Hydrophilic Separation Materials for Liquid Chromatography." Doctoral thesis, Umeå universitet, Kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1350.
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The main focus of this thesis is on hydrophilic interaction chromatography (HILIC) and the preparation of stationary phases for HILIC. The mechanism of HILIC is also discussed; a large part of the discussion has been adapted from a review written by me and professor Irgum for the Journal of Separation Science (ref 34). By reevaluating the literature we have revealed that the notion of HILIC as simply partitioning chromatography needed modification. However, our interest in the HILIC mechanism was mainly inspired by the need to understand how to construct the optimal HILIC stationary phase. The ultimate stationary phase for HILIC is still not found. My theory is that a non-charged stationary phase capable of retaining a full hydration layer even at extreme acetonitrile (> 85%) concentrations should give a HILIC stationary phase with a more pure partitioning retention behavior similar to that of a swollen C18 reversed phase. The preparation of a sorbitol methacrylate grafted silica stationary phase is one of our attempts at producing such a stationary phase. The preparation of such a grafted silica has been performed, but with huge difficulty and this work is still far from producing a column of commercial quality and reprodicibility. This thesis also discusses a new method for the initiation of atom transfer radical polymerization from chlorinated silica. This new grafting scheme theoretically results in a silica particle grafted with equally long polymer chains, anchored to the silica carrier by a hydrolytically stable silicon-carbon bond. The hydrolytic stability is especially important for HILIC stationary phases due to the high water concentration at the surface.
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Wang, Haiying. "STUDIES OF LIQUID CRYSTAL RESPONSE TIME." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3541.
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In this dissertation, the response time issue of the liquid crystal (LC) devices is investigated in meeting the challenges for display and photonic applications. The correlation between the LC director response time and the optical response time is derived theoretically and confirmed experimentally. A major contribution of this thesis is that, based on the small angle approximation, we derive rigorous analytical solutions for correlating the LC director response time to its consequent optical response times (both rise and decay) of a vertical-aligned nematic LC cell. This work successfully fills the gap in the literature of LCD switching dynamics. An important effect related to response time, backflow is analyzed using a homogeneous LC cell in an infrared wavelength. The Leslie viscosity coefficients can hardly be found in the literature. A new effective approach to estimate the Leslie coefficients of LC mixtures based on MBBA data is proposed in this dissertation. Using this method, the Leslie coefficients of the LC material under study can be extracted based on its order parameters. The simulation results agree with the experimental data very well. This method provides a useful tool for analyzing the dynamic response including backflow. Cell gap is an important factor affecting the LC response time. Usually a thinner cell gap is chosen to achieve faster response time, since normally both rise and decay times are known to be proportional to d2. However, they are valid only in the region. In the large voltage region where , the optical decay time is independent of d. In this thesis, we find that between these two extremes the response time is basically linearly proportional to d. Our analytical derivation is validated by experimental results. Therefore, in the whole voltage region, the physical picture of the optical response time as a function of the cell gap is completed. This analysis is useful for understanding the grayscale switching behaviors of the LC phase modulators. In conclusion, this dissertation has solved some important issues related to LC optical response time and supplied valuable tools for scientists and engineers to numerically analyze the LC dynamics.Ph.D.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering
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Jegede, Oluwatoyin Enitan. "Metastable liquid phase separation in Co-Cu alloys." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/19808/.
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Two Co – Cu alloys were studied by drop tube processing technique in a view of investigating the effects of rapid solidification on the phase transformations and microstructural evolution in the metastable alloys. The as – solidified samples had diameters ranging from 53 – 850+ μm and these were analysed using various characterization techniques such as optical (OM) and scanning electron (SEM) microscopy, x- ray diffraction (XRD) and differential thermal analysis (DTA). The Cu – 50 at. % Co alloy was observed to experience liquid phase separation at lower undercooling than the Cu – 68.5 at. % Co alloy. This is found to be in accordance to the asymmetrical metastable miscibility gap determined for the alloy system. Significant number of liquid phase separated structures were observed at cooling rates in excess of 15000 Ks-1, evidenced by a range of microstructural morphologies including stable core shell structures, evolving core shell structures and structures in which the demixed liquid phases were randomly distributed. A large number of these structures experienced multiple liquid phase separation processes. The configuration of the core shell structures were found to be independent of the composition of phases and their relative abundance, with the core always formed by the higher melting point phase. The optimum production of the core shell structures were found to be a function of cooling rate.
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Babinchak, William Michael. "Pathological Aggregation and Liquid-Liquid Phase Separation of TDP-43 in Neurodegenerative Disease." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case158575494511376.
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Wincure, Benjamin 1966. "Computational modeling of a liquid crystal phase transition." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103308.
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This thesis numerically solves the tensor order parameter continuum theory equations for nematic liquid crystals to investigate liquid crystal texturing mechanisms during an isotropic to nematic phase transition in a bulk unstable isotropic phase and next to solid surfaces. The Time Dependent Ginsburg Landau equation with a Landau de Gennes Helmholtz free energy density description is used to predict the shapes, textures and defect mechanisms that occur in the expanding droplets and films of a 4'-pentyl-4-cyanobiphenyl (5CB) nematic phase immediately after their nucleation from an unstable isotropic phase, due to a temperature quench. To create a robust simulation method able to tackle high curvature, defect nucleation, heterogeneous substrates and phase ordering interfaces, particular attention was paid to adapting the mathematical model and computational methods to what was previously known about the nucleation and growth events that occur experimentally during a bulk 5CB isotropic to nematic phase transition and next to decorated solid surfaces. The numerical simulations provide detailed predictions about (i) growth rates for different temperature quenches, (ii) structure of the isotropic-nematic interface, (iii) shapes of expanding nano and submicron nematic droplets, (iv) texturing within growing nano and submicron nematic droplets, (v) a new defect formation mechanism called "interfacial defect shedding", and (vi) the effect of contact angle and interface curvature next to a solid surface with anchoring switches. The main contributions of this thesis are its detailed predictions that emerge from the liquid crystal simulation results, the careful adaptation of the mathematical model and numerical method to what is currently known about early stage growth in a nematic liquid crystal phase, and the validation of new theory by the simulation results.
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Powell, Norman James. "The modelling of nematic liquid crystal phase devices." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5749/.
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The implementation of nematic liquid crystal optical devices, which exploit the voltage dependent, optical path length modification of the electrical Freedrichsz transition, is presented. By combining refractive elements in a diffractive zone structure, efficient and flexible devices with relatively high refractive powers can be constructed. Continuously variable optical properties can be achieved by scaling the optical profile of the refractive elements and applying a phase correction to ensure that the transition between adjacent zones is an integral number of wavelength, hence a continuous optical profile is constructed. Two such devices are postulated; a variable deflection angle prism and a variable focal length lens, though the approach may be extended to other devices. The zones are addressed through combed electrode structures. The required voltage profile is produced by dropping the applied voltages across a shaped conductive strip. A sampling of the profile is transported along the length of the zone via discrete electrodes. In order to produce the required scalability and independent phase correction of the optical profile, it is necessary to restrict the design and operation of the electrodes to the approximately linear region of the response curve. Two-dimensional optical structures can either be achieved through the use of planar earth plates, to mask connections to the centre of the device, or by cascading devices with electrode structures open to connection at the edges. In order to predict the optical profiles of these and other devices, a model was constructed which describes the director orientation through a two-dimensioned electrode structure. The variational finite element method was employed to minimize the electrical Gibbs free energy of a liquid crystal cell, in order to find the equilibrium director orientation. A preliminary version of this model is presented which is restricted to rotation of the liquid crystal to within the plane of the solution.
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Zhang, Zichen. "Phase-only nematic liquid crystal on silicon devices." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610052.
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Tian, Linan. "Liquid crystal blue phase for electro-optic displays." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/liquid-crystal-blue-phase-for-electrooptic-displays(0230a0fd-6cbb-4edb-a626-ae981fe75141).html.
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Liquid crystals are a vast and diverse class of materials which ranges from fluids made up of simple rods, polymers and solutions, to elastomers and biological organisms. Liquid crystal phases are neither crystalline, nor a ‘normal’ isotropic liquid, but lie somewhere in between these two common states of matter. Liquid crystals have found enormous use in display devices due to their electro-optic properties. In this thesis, the optical and electro-optical properties of some chiral liquid crystalline phases are studied. The optical and electro-optical behaviour of liquid crystalline blue phases has been investigated via a detailed analysis of the reflection spectrum from thin, vertical field (VF) cells. Spectral analysis in this thesis was performed using a numerical fitting technique based on the Berreman 4x4 matrix method. The validity of the technique was proved through comparisons of independent measurements with the calculated physical parameters. A novel Kerr effect measurement method was proposed in this thesis and a known material was used to verify this new method. The Kerr constant together with its dispersion relation was measured using a white light source. An unusually large Kerr constant, K, is determined in the blue phases of a non-polymer stabilized material, ~ 3x10-9 mV-2 (BPI). The large value of K is attributed to significant pre-transitional values of the dielectric anisotropy and birefringence. K follows an inverse dependence on temperature which is more marked in BPII than BPI, and we consequently suggest that the BPI demonstrates properties best suited to electro-optic devices. The field effects in blue phase include electrostriction and the influence of the Kerr effect was separated from electrostriction phenomena for the first time in this work. Finally in the Kerr effect measurements, the Kerr constant in the optically isotropic dark conglomerate phase of a bent-core material was studied for the first time, with rather low values, ~1x10-11 mV-2. The low Kerr constant can be understood in the context of the physical properties of the material. Supercooling phenomena in the blue phase were studied through an analysis of the optical properties in thin cells. Features including the Bragg reflection peak jump and hysteresis are measured through the reflection spectra. A blue phase sample with a single orientation over an area of millimeters was prepared to help the spectra study of the blue phases. Although some previous reports indicated that there may be a new blue phase in the supercooled region, we find that there is no evidence shows that the supercooled blue phase has a different structure from the BPI.Chiral molecules have been included as dopants in achiral bent-core materials to produce a range of new chiral mixtures. Different host materials and chiral dopants have been used to produce several chiral nematic materials in which the chiral nematic phase, the underlying smectic phase and the blue phases are examined. The order parameter is determined as a function of temperature in the chiral nematic phase, and compared to that determined for several calamitic materials; no discernible difference is found. A study of the pitch divergence in the chiral nematic phase of the bent-core mixtures shows interesting properties at both low temperature (as the smectic phase is approached) and at high temperatures (at the transition to the blue phase). An unusual phase separation of the chiral dopant in the mixtures is reported, and details are deduced through a comparison between different mixtures. It is found that a dopant with similar clearing point to the bent-core material has less likelihood of phase separation. Although the blue phase temperature range is extended in these mixtures in comparison with typical values for calamitic materials, it does not extend beyond 2K in any of the materials. Both blue phase I and the fog phases are observed in these chiral bent core systems, but no BPII is observed in any of the materials studied. The small k33 (~ 2.8 pN at 10 K below clearing point) in the bent-core host material is suggested as one of the reasons that the blue phase range is not enhanced as much as may have been expected from reports by other authors.
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Mottram, N. J. "Boundary effects in nematic liquid crystal layers." Thesis, University of Bristol, 1996. http://hdl.handle.net/1983/3f718f68-e280-4994-afa2-29a7845c73f7.
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Huaiyu, Yang. "Crystallization of Parabens : Thermodynamics, Nucleation and Processing." Doctoral thesis, KTH, Teknisk strömningslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122228.
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In this work, the solubility of butyl paraben in 7 pure solvents and in 5 different ethanol-water mixtures has been determined from 1 ˚C to 50 ˚C. The solubility of ethyl paraben and propyl paraben in various solvents has been determined at 10 ˚C. The molar solubility of butyl paraben in pure solvents and its thermodynamic properties, measured by Differential Scanning Calorimetry, have been used to estimate the activity of the pure solid phase, and solution activity coefficients. More than 5000 nucleation experiments of ethyl paraben, propyl paraben and butyl paraben in ethyl acetate, acetone, methanol, ethanol, propanol and 70%, 90% ethanol aqueous solution have been performed. The induction time of each paraben has been determined at three different supersaturation levels in various solvents. The wide variation in induction time reveals the stochastic nature of nucleation. The solid-liquid interfacial energy, free energy of nucleation, nuclei critical radius and pre-exponential factor of parabens in these solvents have been determined according to the classical nucleation theory, and different methods of evaluation are compared. The interfacial energy of parabens in these solvents tends to increase with decreasing mole fraction solubility but the correlation is not very strong. The influence of solvent on nucleation of each paraben and nucleation behavior of parabens in each solvent is discussed. There is a trend in the data that the higher the boiling point of the solvent and the higher the melting point of the solute, the more difficult is the nucleation. This observation is paralleled by the fact that a metastable polymorph has a lower interfacial energy than the stable form, and that a solid compound with a higher melting point appears to have a higher solid-melt and solid-aqueous solution interfacial energy. It has been found that when a paraben is added to aqueous solutions with a certain proportion of ethanol, the solution separates into two immiscible liquid phases in equilibrium. The top layer is water-rich and the bottom layer is paraben-rich. The area in the ternary phase diagram of the liquid-liquid-phase separation region increases with increasing temperature. The area of the liquid-liquid-phase separation region decreases from butyl paraben, propyl paraben to ethyl paraben at the constant temperature. Cooling crystallization of solutions of different proportions of butyl paraben, water and ethanol have been carried out and recorded using the Focused Beam Reflectance Method, Particle Vision and Measurement, and in-situ Infrared Spectroscopy. The FBRM and IR curves and the PVM photos track the appearance of liquid-liquid phase separation and crystallization. The results suggest that the liquid-liquid phase separation has a negative influence on the crystal size distribution. The work illustrates how Process Analytical Technology (PAT) can be used to increase the understanding of complex crystallizations. By cooling crystallization of butyl paraben under conditions of liquid-liquid-phase separation, crystals consisting of a porous layer in between two solid layers have been produced. The outer layers are transparent and compact while the middle layer is full of pores. The thickness of the porous layer can reach more than half of the whole crystal. These sandwich crystals contain only one polymorph as determined by Confocal Raman Microscopy and single crystal X-Ray Diffraction. However, the middle layer material melts at lower temperature than outer layer material.QC 20130515
investigate nucleation and crystallization of drug-like organic molecules
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Al-Zangana, Shakhawan. "Nano- and micro-particle doped liquid crystal phases." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/nano-and-microparticle-doped-liquid-crystal-phases(31dbb051-7d9c-4780-bda0-d58773846de0).html.
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This thesis presents the investigation of the liquid crystal (LC) - particle suspensions. Particles from nano- to micro-size, spherical to two-dimensional shapes, with different functionality are dispersed into nematic and smectic phases. The aim is to create ordered nanoparticle (NP) assemblies and thereby modify the common properties of the liquid crystal, such as dielectric anisotropy and electro-optical, revealing any interaction between particles and LC properties. It is found that for concentrations (>0.5vol%), the ferroelectric NPs have increased the sensitivity of the nematic liquid crystal to the electric field through electro-optical responses, which is seen by an enhancement in the dielectric anisotropy. This could be induced by the coupling of the electrical dipole moments in the spherical NPs with the LC director field. The electro-optical properties of the chiral smectic (SmC*) phase (tilt angle Θ, switching time τ_s and spontaneous polarisation P_s) are found to be independent of the concentration and sizes of the doped NPs. The relaxation frequency f_R of the Goldstone mode is faster in the ferroelectric NPs suspensions of 2.0vol% compared to the paraelectric NPs. In the graphene oxide (GO) - nematic LC (5CB) suspensions, the small GO sizes of mean size 560 nm are more easily dispersible than larger flakes of 2.8 micro metre mean size. As the GO concentration is increased, each of the threshold voltage and splay elastic constant dramatically increases, reaching saturation at ≈1.0wt%. The field driven switching-on time is practically not affected, while the purely elastically driven switching-off time is strongly sped-up. Interestingly, thermotropic and lyotropic LC phases are exhibited in the GO-5CB suspensions when heating the thermotropic liquid crystal into its isotropic phase. The isotropic phase of 5CB acts as a solvent for the GO particles, forming a lyotropic nematic phase with largely reduced birefringence. It is found that the nematic to isotropic phase transition is shifted toward higher temperature for the GO-5CB system compared to the BaTiO3-5CB system. Dispersions of different sizes of GO flakes are prepared in isotropic and nematic fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature range (25-60 ℃) and frequency range (100 Hz-2 MHz). The mixtures containing GO flakes were found to exhibit varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. The relaxation frequencies in the isotropic media were lower compared to the nematic medium. Relaxation frequencies (~10 kHz) are observed in the GO-isotropic media, which are reduced as the size of the GO flakes are decreased, are anticipated to be inherited from GO flakes. However, the fast relaxations (~100 kHz) that are observed in the nematic suspensions could imply strongly slowed down molecular relaxation modes of the nematogenic molecules. Finally, the phase diagram of lyotropic LC as a function of the lateral dimensions of the GO flakes, their concentration, geometrical confinement configuration and solvent polarity was investigated. Polarising optical microscopy was used to determine isotropic-biphasic-nematic phase evolution. The confinement volume and geometry of the sample relative to the GO size are shown to be vital to the observation of the lyotropic phase. GO LCs have the potential for a range of applications from display technologies to conductive fibres. The confinement related LC phase transition is critical toward their applications. It is also found that the stability of the LC phase is higher for the solvent of higher dielectric constant.
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Fukuda, Junichi. "Phase Separation of Liquid Crystalline Polymers -Statics and Dynamics-." 京都大学 (Kyoto University), 1999. http://hdl.handle.net/2433/157171.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第7631号
理博第2016号
新制||理||1081(附属図書館)
UT51-99-G225
京都大学大学院理学研究科物理学・宇宙物理学専攻
(主査)教授 小貫 明, 教授 蔵本 由紀, 教授 吉川 研一
学位規則第4条第1項該当
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JAIN, ABHISHEK. "DEVELOPMENT OF MEMBRANES FOR LIQUID PHASE ETHANOL-WATER SEPARATION." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1109038241.
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Manolis, Ilias G. "Electrically addressed liquid crystal phase gratings for optical switches." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/251845.
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Lee, Y. "Characterisation of phase modulating liquid crystal on silicon devices." Thesis, University of Edinburgh, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.653757.
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The objective of the work described in this thesis was to optimize the optical phase modulating properties of liquid crystal on silicon (LCoS) devices for non-display applications. This thesis presents the characterization of oxide two deposition processes, modelling of binary phase modulation in ferroelectric liquid crystal SLMs using electronic equivalent circuit, and characterization of multi-phase modulation in nematic liquid crystal with pulse-width modulation. For optimal optical performance of a phase modulating LCoS device, the degree of surface planarisation of the CMOS backplane has to be superior to that of conventional CMOS. Two oxide-deposition processes have been characterized to evaluate their effectiveness in planarising microdisplay backplanes. In order to investigate the trench-filling capabilities of the respective oxide deposition processes, I prepared test samples that had a set of trench patterns (1 - 6 μm wide) etched into 4 μm -thick thermal oxide on a Si-substrate. I found that the trench filling capability of an electron cyclotron resonance chemical vapor deposition (ECR CVD) process is superior to that of a pyrolytic CVD process. I investigated the effects of ECR CVD deposition parameters on trench-filling properties and demonstrated the ability to produce deposited oxide layers which fill high aspect ratio trenches without producing voids. Modelling of binary phase modulation is required for optimal performance of ferroelectric liquid crystals on silicon SLMs when used in coherent optical systems. This thesis presents a modelling technique by which an HSpice model can be provided for characterization of phase modulation properties for designing FLC-on-silicon SLMs. The simulation and experimental measurements of phase modulation are described. For the theoretical model simulation, FLC parameter measurements are described. I experimentally verified the modeled prediction of phase modulation by investigating reflective FLC test cells. I have shown reasonable agreement within 9 % between the measured and simulated values of phase modulation. In phase modulating diffractive optical devices multi-phase modulation provides improved performance over binary modulation. Multi-phase modulation can be achieved by using nematic liquid crystal spatial light modulators (NLCSLM) with pulse-width modulation driven from a binary CMOS backplane. This thesis presents the characteristics and the driving scheme of the 512x512 Si-backplane SLM for the implementation of the multi-phase modulation while comparing the binary and four-level phase holograms. A diffraction efficiency of 39.7% for binary grating and 72.7% for four-level blazed grating were obtained at a spatial frequency of 0.78 lines per mm.
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Mills, Stuart James. "A computer simulation study of liquid crystal phase coexistence." Thesis, Sheffield Hallam University, 1999. http://shura.shu.ac.uk/20065/.
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Results are presented from a variety of molecular simulations of phase coexistence using the well established Gay-Berne (GB) liquid crystal model. Firstly, the simulation of bulk phase coexistence using the Gibbs ensemble Monte Carlo technique is presented, both for one and two-component GB systems. The one-component results, using a novel parameterisation of the GB, show a rich phase behaviour, displaying both isotropic and nematic-vapour coexistence, in good comparison with previous studies. A method for arriving at the two-component parameterisation is then discussed, followed by a novel application of the Gibbs ensemble to the isotropic-nematic transition in two-component systems. Results in broad agreement with theoretical predictions, subject to a large finite size effect, are obtained. Secondly, upon the basis of the one-component Gibbs results, results are presented from a series of molecular dynamics simulations of a free standing GB film in equilibrium with its own saturated vapour. The introduction of inhomogeneity is shown to induce a preferred molecular alignment in the nematic film perpendicular to the liquid-vapour interface. At slightly higher temperatures the nematic film is wet by the isotropic phase, displaying an intermediate ordering regime where the formation of short-lived nematic domains within the film is observed. This effect has been analysed using orientational correlation functions, and shown to result from a decoupling of the planar and perpendicular nematic ordering caused by the system inhomogeneity. A system-size analysis of this effect has also been undertaken, showing a definite increase in the range of decay of these orientational correlations with increasing system size.
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Jamali, Afsoon Jamali. "LARGE AREA TUNABLE LIQUID CRYSTAL LENS." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1541671894328594.
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Kolli, Hima Bindu. "Unconventional Liquid Crystal Phases of Helical Particles." Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/15358.
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Helical particles are ubiquitous in nature. Many natural and synthetic biomolecules like polynucleotides and polypeptides; colloidal suspensions like filamentous (fd) virus and helical flagella and certain organic molecules are found in helical shape. Despite their abundance in nature, understanding of the phase behaviour of helical particles is poor. These helical molecules have a well known propensity to form liquid crystal phases. The chirality in the helical shapes influence their liquid crystal organization. Experimental results of the liquid crystal phases shown by these molecules are often compared to those of rods, neglecting the effect of helical shape on phase behaviour. We have undertaken an extensive investigation of the phase diagram of hard helical particles using Monte Carlo simulations. We provide evidence of new chiral phases exhibiting screw-like order. This new chiral phase is different to the cholesteric phase and is characterized by the C2 symmetry axes of helices spiralling around the nematic director with periodicity equal to the particle pitch. We have used Isobaric Monte Carlo simulations to obtain a full phase diagram of helical particles. A rich polymorphism is observed exhibiting a special screw-like nematic and a number of screw-like smectic phases. The effect of helical shape on the phase diagram is studied by considering different shapes of helix obtained by tuning the helical parameters like radius and pitch. We found a remarkable change in the phase behaviour with the change in the shape of helix. Dense packing structures of different helical shapes are found by implementing Isopointal set Structural Search Method (ISSM). The physical mechanism underlying the liquid crystal order observed in helical flagella is explained. Finally, some results are shown discussing the relation between the pitch and the handedness of cholesteric phase and the shape of the helix.
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Bemrose, Richard Antony. "A molecular dynamics study of liquid crystal mixtures." Thesis, Sheffield Hallam University, 1999. http://shura.shu.ac.uk/19339/.
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Results are presented from molecular dynamics simulations of binary liquid crystal mixtures using a generalisation of a well established Gay-Berne intermolecular potential. The simulations are undertaken in both the microcanonical (NVE) and the isoenthalpic-isobaric (NPH) ensembles. Firstly a 50:50 mixed system is simulated in the NVE ensemble containing generalised Gay-Berne (GGB) rod-like molecules with length to breadth axial ratios of 3.5:1 (molecules A) and 3:1 (molecules B). The molecules in this system differs only slightly from the well-characterised Gay-Berne (GB) potential with length to breadth ratio of 3:1. It is shown that the system exhibits isotropic (/), nematic (N) and smectic-B (SmB) phases with both the I-N and N-SmB phase boundaries not clearly defined. Competition between two density waves parallel to the director of the same wavelength but different phase lead to a pre-smectic ordering preceding the N-SmB phase transition. The longer molecules are shown to have a consistently higher order parameter the difference being greatest in the nematic phase and decrease with lowering temperature. Although a degree of local ordering is shown within each smectic layer the smectic phase is fully commensurate. Secondly, phase behaviour diagrams are presented from a series of constant-NPH simulations over a range of pressures and concentrations. The binary mixtures exhibit a rich phase behaviour, displaying isotropic, nematic, smectic-A (SmA), induced smectic-A and smectic-B phases depending on the choice of pressure and concentration. It is shown that the temperature range over which the nematic phase is stable can be extended greater than either homogeneous system by elevating the system pressure and/or by choice of concentration, agreeing with experimental results. The mixture exhibits a stable SmA island at a mole fraction of xa = 0.50 depending on the choice of pressure and a narrow induced SmA phase at xa = 0.25.
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Zhang, Liqin. "A new liquid-liquid partitioning system for bioseparations at low temperatures." Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1184618209.
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Adechy, Didier. "Phase separation in annular gas-liquid flows at t-junctions." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251963.
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Eliasson, Anders. "Liquid phase sintering of W-Ni-Fe composites : liquid penetration, agglomerate separation and tungsten particle growth." Doctoral thesis, KTH, Keramteknologi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3870.
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The initial stage of liquid phase sintering, involving liquid penetration, agglomerate separation, particle spreading and growth has been investigated in experiments using tungsten heavy alloys. The particle composites used were produced by hot isostatic pressing (HIP) of pure powder mixtures of W-Ni-Fe-(Co). By using different HIP temperatures, volume fractions of tungsten, alloying elements like Cobalt and Sulphur or excluding Iron from the matrix, liquid penetration, agglomerate separation and particle growth conditions were affected. The investigations were performed mainly under microgravity (sounding rockets or parabolic trajectories by airplanes) but at high tungsten particle fractions, short sintering times or at infiltration of solid pure tungsten, they were performed at normal gravity. The liquid penetration of the tungsten agglomerates is explained by initial wetting under non-equilibrium conditions, due to the reaction between the liquid matrix and the particles, and a decrease of interfacial energy. The dissolving of tungsten gives a pressure drop in the penetrating liquid and a driving force for the liquid movement by a suggested parabolic penetration model. For cold worked tungsten, a penetration theory was proposed, where an internal stress release in the penetrated tungsten grains creates space for the advancing liquid. The spreading of the tungsten agglomerates is explained by an interagglomerate melt swelling due to a Kirkendall effect. The liquid matrix undergoes a volume increase since the diffusion rates of Ni-Fe are higher than for W and initial concentration gradients of W and Ni, Fe exists. The suggested model by Kirkendall are also used for an analysis of the interaction behaviour between solid particles and a solidification front and inclusion behaviour in iron base alloys during teeming and deoxidation. The average tungsten particles size decrease initially since part of the tungsten particles is dissolved when the non-equilibrium matrix phase is melting. When equilibrium is reached, the tungsten particles grow in accordance with the Ostwald ripening process by an approximately 1/3 power law. Larger particle fraction of particles showed a higher growth rate, due to shorter diffusion distances between the particles. Cobalt, Sulphur and absence of iron in the matrix were found to increase the growth rate of the tungsten particles due to a higher surface tension between the solid tungsten particles and the matrix melt.QC 20100528
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Starzomski, Mark Stephen. "Characterization and applications of the phase-modulating liquid crystal display." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0016/MQ48289.pdf.
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Chen, Kuan Ming. "Submillisecond-response blue phase liquid crystals for display applications." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5158.
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With exploding growth of information exchanges between people, display has become indispensable in our daily lives. After decades of intensive research and development in materials and devices, and massive investment in manufacturing technologies, liquid crystal display (LCD) has overcome various obstacles and achieved the performance we need, such as wide viewing angle, high contrast ratio, and high resolution, etc. These excellent performances make LCD prevailed in every perspective. Recently, with the demands of energy conservation, a greener LCD with lower power consumption is desired. In order to achieve this goal, new energy-effective driving methods, such as field sequential color display, have been proposed. However, in order to suppress color breakup the LC response time should be faster than 1 ms. To overcome this challenge, various fast-response liquid crystal modes, such as thin cell gap, low viscosity materials, overdrive and undershoot voltages, polymer stabilization, and ferroelectric liquid crystal, are under active investigations. Among these approaches, blue phase liquid crystal (BPLC) shows a greater potential with less fabrication limitations. In this dissertation, the feasibility of polymer-stabilized blue phase liquid crystal for display applications is explored starting from the building blocks of the material system, polymer-stabilization processes, test cell preparations, electro-optical (EO) properties, to suggested approaches for further improvements. Because of the nature of blue phase liquid crystals, delicate balance among system components is critically important. Besides the properties of each composition, the preparation process also dictates the EO performance of the self-assembled nano-structured BPLC composite. After the preparation of test cells, EO properties for display applications are investigated and results described. Approaches for further improvements of the EO properties are also suggested in the final part of this dissertation.ID: 031001409; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Title from PDF title page (viewed June 12, 2013).; Thesis (Ph.D.)--University of Central Florida, 2012.; Includes bibliographical references (p. 82-89).
Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
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Waichigo, Martin M. "Alkylammonium Carboxylates as Mobile Phases for Reversed-Phase Liquid Chromatography." Miami University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1134142423.
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Oprisan, Ana. "Fluctuations, Phase Separation and Wetting Films near Liquid-Gas Critical Point." ScholarWorks@UNO, 2006. http://scholarworks.uno.edu/td/435.
Full textAbstract:
Gravity on Earth limits the study of the properties of pure fluids near critical point because they become stratified under their own weight. Near the critical point, all thermodynamic properties either diverge or converge and the heating and cooling cause instabilities of the convective flow as a consequence of the expansibility divergence. In order to study boiling, fluctuation and phase separation processes near the critical point of pure fluids without the influence of the Earth's gravity, a number of experiments were performed in the weightlessness of Mir space station. The experimental setup called ALICE II instrument was designed to suppress sedimentation and buoyancy-driven flow. Another set of experiments were carried out on Earth using a carefully density matched system of deuterated methanolcycloxexane to observe critical fluctuations directly. The set of experiments performed on board of Mir space station studied boiling and wetting film dynamics during evaporation near the critical point of two pure fluids (sulfur hexafluoride and carbon dioxide) using a defocused grid method. The specially designed cell containing the pure fluid was heated and, as a result, a low contrast line appeared on the wetting film that corresponded to a sharp change in the thickness of the film. A large mechanical response was observed in response to the cell heating and we present quantitative results about the receding contact lines. It is found that the vapor recoil force is responsible for the receding contact line. Local density fluctuations were observed by illuminating a cylindrical cell filled with the pure fluid near its liquid- gas critical point and recorded using a microscope and a video recorder. Microscopic fluctuations were analyzed both in sulfur hexafluoride and in a binary mixture of methanol cyclohexane. Using image processing techniques, we were able to estimate the properties of the fluid from the recorded images showing fluctuations of the transmitted and scattered light. We found that the histogram of an image can be fitted to a Gaussian relationship and by determining its width we were able to estimate the position of the critical point. The characteristic length of the fluctuations corresponding to the maximum of the radial average of the power spectrum was also estimated. The power law growth for the early stage of the phase separation was determined for two different temperature quenches in pure fluid and these results are in agreement with other experimental results and computational simulations.
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Kanao, Eisuke. "Studies on π-interactions in liquid phase separations." Kyoto University, 2020. http://hdl.handle.net/2433/254521.
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Nishiyama, Isa. "The effect of chirality on ferroelectric and related liquid crystal systems." Thesis, University of Hull, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307759.
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Kelly, Thu-Lan. "Liquid crystal spatial light modulators as computer controlled optical elements /." Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phk298.pdf.
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Huang, Tsang-Min. "Phase Equilibria of Binary Liquid Crystal Mixtures Involving Induced Ordered Phases." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1284381816.
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Hsieh, Chia-Rong, and 謝佳蓉. "Phase Separation Studies of Polymer-Dispersed Cholesteric Liquid Crystal film." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/54yvxv.
Full textAbstract:
碩士國立臺北科技大學
有機高分子研究所
98
In this study, we report a single-substrate method for fabrication of reflective and bistable cholesteric liquid crystal displays on substrates based on “polymer-dispered liquid crystal” of liquid crystal in a polymer matrix to create a close-packed monolayer. The displays may be on a large scale and exhibit switching voltages and reflectance approaching two-substrate “polymer-dispered liquid crystal” method.
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LIN, CHUN-YUAN, and 林群淵. "Studies of Phase Separation for a Polymer-Dispersed Cholesteric Liquid Crystal." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/12289440532699741837.
Full textAbstract:
碩士逢甲大學
資訊電機工程碩士在職專班
93
In this thesis, we study the photo-induced phase separation between liquid crystal and polymer and electro-optical property a polymer dispersed cholesteric liquid crystal (PDCLC). By tuning polymer concentration and UV exposure intensity, we achieved the morphology of green-and-black in PDCLC. Further, the characteristics of driving voltage, reflective spectrum, grain size, R-V curve, and response time were investigated. We obtained the reflectivity of 21.5% and 20% for 4mm and 10 mm cell gap samples, in which the driving voltages were 56V and 100V, respectively.