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Dissertations / Theses on the topic 'Liquid crystals. Polymer liquid crystals'

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Published: 4 June 2021

Last updated: 9 February 2022

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1

Wu, Haixia. "Anchoring Behavior of Chiral Liquid Crystal at Polymer Surface: In Polymer Dispersed Chiral Liquid Crystal Films." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04082004-154054/unrestricted/wu%5Fhaixia%5F200405%5Fmast.pdf.

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Thesis (M.S.)--Textile and Fiber Engineering, Georgia Institute of Technology, 2004.
Griffin, Anselm, Committee Member; Srinivasarao, Mohan, Committee Chair; Park, Jung O., Committee Member. Includes bibliographical references (leaves 101-105).

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2

Legge, Coulton Heath. "Structural modifications in liquid crystals and liquid crystal polymers." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306164.

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3

Zhang, Guoqiang. "Stressed Liquid Crystals: Properties and Applications." [Kent, Ohio] : Kent State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1184972979.

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Thesis (Ph.D.)--Kent State University, 2007.
Title from PDF t.p. (viewed Mar. 4, 2009). Advisor: John West. Keywords: liquid crystal, polymer, shear, structure, application Includes bibliographical references (p. 252-267).

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4

Hicks, Sarah Elizabeth. "Polymer-Dispersed and Polymer-Stabilized Liquid Crystals." Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1333417859.

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5

Kim, Sang Hwa. "Fast Switching Polymer Stabilized Liquid Crystal Devices: Morphological and Electro-Optical Properties." [Kent, Ohio] : Kent State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1101220722.

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6

Silvestri, Regan L. "Spectroscopic characterization of the structure and motion of polymer liquid crystals and polymer dispersed liquid crystals." Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1057587237.

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7

Pena, Ricardo. "Polymeric liquid crystals as potential processing aids." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/9138.

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8

Haley, William Charles Jr. "The synthesis and asymetric reduction of a liquid crystalline polymer." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/11040.

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9

Burnham, Kikue Sugiyama. "Phototriggers for a liquid crystal-based optical switch." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/27900.

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10

Bladon, Peter. "Phase transitions in nematic polymer liquid crystals." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307042.

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11

Namba, Takashi. "A synthesis of a new liquid crystal polyester." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/8641.

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12

Denisov, Alexey. "Reconfigurable photonic crystals : external field structuring of liquid crystals - polymer composites." Télécom Bretagne, 2009. http://www.theses.fr/2009TELB0104.

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Cette thèse concerne l'étude des composites cristaux liquides (CL) / polymère. Notre but est de concevoir et de fabriquer des cristaux photoniques dont la structure soit reconfigurable par l'action d'un champ appliqué, électrique ou lumineux. Notre première réalisation se base sur l'utilisation de cristaux liquides cholestériques (CLC) stabilisés par un polymère. Les CLC présentent naturellement une structure hélicoïdale périodique, et sont donc des cristaux photoniques à une dimension pour certaines longueurs d'ondes. Pour former un cristal photonique bidimensionnel, nous avons induit une modulation périodique de la structure CLC dans une seconde direction en appliquant un champ électrique. Cette structure a permis de montrer expérimentalement un effet de bord de bande et la possibilité d'ajuster la résonance en modifiant le champ appliqué. Notre deuxième approche se base sur l'effet photoréfractif dans les composites cristaux liquides / polymères dopés par des fullerènes. Dans ces matériaux, nous avons photo-inscrit des réseaux unidimensionnels reconfigurables. Pour améliorer l'efficacité et la résolution, nous avons étudié l'influence de la concentration du dopant, utilisant le fullerène C70 ou le dérivé PCBM-60. Nous avons observé une amélioration de la résolution due à l'effet conjoint d'une augmentation de la concentration en dopant et du mécanisme de piégeage des charges dans le réseau polymère. Nous présentons également une nouvelle façon expérimentale d'exploiter l'effet photoréfractif dans des composites cristaux liquides / polymère, permettant d'améliorer l'efficacité de diffraction, pour mieux satisfaire à des besoins d'applications pratiques.

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13

Shafran, Matthew S. "Responsive liquid crystal polymer rods." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5598.

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Thesis (M.S.)--West Virginia University, 2008.
Title from document title page. Document formatted into pages; contains viii, 71 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 63-67).

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14

Nemati, Hossein. "COLOR TUNING IN POLYMER STABILIZED CHOLESTERIC LIQUID CRYSTALS." Kent State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=kent1428717594.

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15

Dong, Shaosheng. "Liquid Crystal Polymers And Dendritic Liquid Crystals: Synthesis, Morphology, Rheology And Binary Mixtures." online version, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1094584392.

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16

Gopalanarayanan, Bhaskar. "Analysis of Thermoplastic Polyimide + Polymer Liquid Crystal Blends." Thesis, University of North Texas, 1998. https://digital.library.unt.edu/ark:/67531/metadc279285/.

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Thermoplastic polyimides (TPIs) exhibit high glass transition temperatures (Tgs), which make them useful in high performance applications. Amorphous and semicrystalline TPIs show sub-Tg relaxations, which can aid in improving strength characteristics through energy absorption. The a relaxation of both types of TPIs indicates a cooperative nature. The semicrystalline TPI shows thermo-irreversible cold crystallization phenomenon. The polymer liquid crystal (PLC) used in the blends is thermotropic and with longitudinal molecular structure. The small heat capacity change (ACP) associated with the glass transition indicates the PLC to be rigid rod in nature. The PLC shows a small endotherm associated with the melting. The addition of PLC to the semicrystalline TPI does not significantly affect the Tg or the melting point (Tm). The cold crystallization temperature (Tc) increases with the addition of the PLC, indicating channeling phenomenon. The addition of PLC also causes a negative deviation of the ACP, which is another evidence for channeling. The TPI, PLC and their blends show high thermal stability. The semicrystalline TPI absorbs moisture; this effect decreases with the addition of the PLC. The absorbed moisture does not show any effect on the degradation. The addition of PLC beyond 30 wt.% does not result in an improvement of properties. The amorphous TPI + PLC blends also show the negative deviation of ACP from linearity with composition. The addition of PLC causes a decrease in the thermal conductivity in the transverse direction to the PLC orientation. The thermomechanical analysis indicates isotropic expansivity for the amorphous TPI and a small anisotropy for the semicrystalline TPI. The PLC shows large anisotropy in expansivity. Even 5 wt. % concentration of PLC in the blend induces considerable anisotropy in the expansivity. Thus, blends show controllable expansivity through PLC concentration. Amorphous TPI + PLC blends also show excellent film formability. The amorphous TPI blends show good potential for applications requiring high thermal stability, controlled expansivity and good film formability.

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17

Chen, Lu Guang, and s3064076@student rmit edu au. "Thermo-Optical Properties of Polymer Dispersed Liquid Crystals." RMIT University. Applied Science, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080206.114823.

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Polymer dispersed liquid crystal (PDLC) films, consisting of micro-sized domains of a liquid crystal dispersing in a polymer matrix, serve as the basis of a variety of high-efficiency electro-optical effects. The thermo-optical properties of the PDLCs were investigated in this thesis. The thermal properties and the morphologies of four low molar mass mesogens were studied by DSC and polarized optical microscope (POM). There were significant super cooling/heating effects on the first order phase transitions but not on the mesophase transitions. The structural effects on the transition temperature were investigated. Between the two 4-alkoxybenzoic acids mesogens, the clearing temperature of 4-(octyloxy)benzoic acid was higher than 4-(decyloxy)benzoic acid because of the increasing chain length. Trans-4-methoxycinnamic acid had the highest melting temperature among the four mesogens despite the molar mass because the carboxylic acid termini of trans-4-methoxycinnamic acid gave rise to strong intermolecular attractions. The smectic phases of 4-(octyloxy)benzoic acid were classified as head-to-head bilayer orientational smectic structures, SmA2 and SmC2, respectively, by wide angle X-ray diffraction through measuring the d spacing of the liquid crystal. The total solubility parameter was used to evaluate matching a polymer-LC-solvent combination. PDLC films were prepared by the solvent induced phase separation method and suitable morphologies were achieved by thermal induced phase separation. The phase transition temperatures of PDLCs were shifted to a lower temperature due to the polymer dispersion effects. Different mesophases were observed in PDLC films when LC exhibited different mesophases. The LC fractions in the droplets were calculated from the nematic to isotropic enthalpies through the Smith equation. Two factors, thermal cooling rate and the LC concentration, which affect the size of the droplet dispersed in the polymer matrix, were investigated in the PVC dispersed 4,4'-azoxyanisole. The phase transitions of pHEMA dispersed 4-(octyloxy)benzoic acid and PVC dispersed 4,4'-azoxyanisole were investigated by TMDSC and quasi-isothermal TMDSC. The TMDSC results were analysed by the two approaches, reversing and non-reversing heat flow and complex heat capacity. The results of the phase transitions of the two PDLCs illustrated that in the PDLCs it involved both non-reversing, melting, and reversing, clearing and the transition between two mesophases. In the non-reversing transition, the transition temperature would be affected by super cooling/heating and the results obtained in the experiments were dependent on the experimental conditions, such as the heating or cooling rate, sample size and purge gas flow rate. However, in the reversing transition process, there were no super cooling/heating effects observed and it seemed that the experimental conditions were not so critical. Results could be monitored by Lissajous figures obtained from the quasi-isothermal TMDSC. The plots of modulated heat flow versus the derivative of modulated temperature can be used to alert to unfavorable experimental conditions where loss of system linearity could be seen.

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18

Blonski, Slawomir. "Computer Simulations of Mechanical Behavior of Polymer Liquid Crystals." Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc332725/.

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In this dissertation molecular dynamics simulations of behavior of polymer liquid crystals (PLC's) under tensile deformation have been performed. PLC's composed of random or block copolymers of rigid and flexible segments have been studies. Systems of fully flexible chains have been simulated for comparison. Stress-strain relations and fracture mechanics have been investigated.

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19

Zhang, Hailiang. "Wavelength Tunable Devices Based on Holographic Polymer Dispersed Liquid Crystals." Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1203610126.

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20

McHattie, Gillian S. "Ion transport in liquid crystalline polymer electrolytes." Thesis, University of Aberdeen, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324432.

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A systematic study of structure-property relations has been carried out on a range of polymers, both with and without mesogenic moieties. These materials have been characterised using various thermal techniques, including DSC and DMTA. These polymers have been complexed with LiClO₄ and the effects of the salt on thermal characteristics have been investigated. In addition, AC impedance spectroscopy has been employed to determine the temperature dependence of the conductivity of these complexes. Results suggest that polymers with mesogenic side groups have the potential to exhibit a conduction mechanism which is independent of both the glass transition temperature of the complex as determined by DSC and the corresponding structural relaxation detected using DMTA. It is found that the glass transition temperature of these materials is determined primarily by the side groups, and not by the polymer backbone. A model is thereby proposed in which ionic motion is decoupled from Tg, but still dependent on the local viscosity of the ionic environment. Appreciable conductivity is therefore observed below the glass transition temperature of the complex, thus resulting in dimensionally stable polymeric complexes with possible applications as solid state electrolytes in batteries.

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21

Bara, Jason Edward. "New ionic liquids and ionic liquid-based polymers and liquid crystals for gas separations." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256439.

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22

Zeng, Erman. "Synthesis and characterization of HBA/HNA star-copolyester." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/10055.

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23

Zeng, Erman. "Design, synthesis and characterization of columnar discotic and bowlic liquid crystals." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12268.

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24

Shinton, S. E. "Optical and dielectric properties of polymer dispersed liquid crystals." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639025.

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Polymer Dispersed Liquid Crystals (PDLCs) are attracting considerable attention for new optical displays. This thesis describes the synthesis of PDLC materials, fabrication of cells and study of their optical and dielectric behaviour. This work includes two areas of research. Predominantly it is an investigation of the properties of PDLCs prepared using Polymerisation Phase Separation (PIPS) by UV irradiation of mutually soluble liquid crystal (LC) and pre-polymer materials, developed for use in PDLC systems. A limited study of liquid crystal gels completes the thesis. We demonstrate that the electro-optical response of a PDLC is due to alignment of the LC phase, illustrated by comparison of the dielectric behaviour of the PDLC and LC in an aligning field. It is evident from this work that there is solubility of the LC component in the polymer that forms the continuous phase. Therefore, only at higher concentrations of the LC component (above 30%) will the PDLC be formed, and in such materials, the continuous phase contains dissolved LC material. Variation of experimental conditions under which samples are prepared, by changing the composition, temperature of cure and the presence of aligning fields, leads to modifications in the structure and properties of PDLCs, which are investigated. Techniques to study the dielectric, electro-optic and optical properties have been applied to the range of samples prepared. Such studies give information on the alignment of the LC phase in a PDLC in directing electric fields. It is demonstrated that dielectric relaxation spectroscopy (DRS) provides direct information on the macroscopic orientation and voltage induced changes in the alignment of gels produced in the presence and absence of electric fields. Our studies show that DRS, in combination with optical techniques, provides a powerful means for studying the alignment of LC molecules in PDLCs and gels.

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25

Brittin, Mark. "Analytical and morphological studies of polymer-stabilised liquid crystals." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297785.

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26

Jenkins, Shawn Eric. "Synthesis and spinning of a new thermotropic liquid crystallinepolymers : characterization of fiber morphology and mechanical properties." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/8557.

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27

Luo, Shijian. "Synthesis and charaterization of chiral 2-methyl-1,4-cyclohexanedicarboxylic acid and its polyamide." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/8606.

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28

Wusik, Martin Joseph. "The synthesis and characterization of a regularly alternating copolyester." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/8708.

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29

Zhou, Jian. "Study of Anchoring Behavior of Nematic Fluids at The Interface of Polymer-Dispersed Liquid Crystals." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5121.

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A liquid crystal (LC) at its boundary surface adopts a preferential alignment, which is referred to as anchoring. The direction of this alignment (i.e., anchoring direction) may be perpendicular, parallel or tilted with respect to the surface. Transitions from one anchoring condition to another may occur when the parameters (e.g., temperature) charactering the surface change, as referred to as anchoring transitions. In the LC-polymer composite systems under our study, the anchoring and temperature- driven anchoring transitions of nematic fluids is very sensitive to the structure of the side chain of poly (alkyl acrylate) matrixes that encapsulate the LC. We have shown that the anchoring transition temperature of these systems can be tuned far below the nematic-to-isotropic transition temperature, by varying either the length, branching structure of the side chains of homopolymers, or the composition of copolymer of two dissimilar monomers. Both sharp and broad anchoring transitions with respect to the temperature range over which a transition occurs were observed. It is postulated that microscopic interactions between the polymer side chains and LC molecules play an important role in determining the anchoring. In particular, the conformation of the polymer side chain is proposed to have important control over the anchoring. Anchoring strength and tilt angle as a function of temperature during the anchoring transitions were also experimentally investigated, which contribute to understanding of the microscopic mechanism for such transitions. Based on the LC-polymer composites with controlled anchoring, a LC display with reverse switching mode and a novel electrically switchable diffraction grating have been demonstrated. The advantages of these devices are ease of manufacturing, low operation voltage, and mechanical stability offered by polymer matrix. Moreover, a detailed study of the director configuration of wall defects found in these composite films was carried out using fluorescence confocal polarized microscopy.

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30

Jiang, Yingfei. "FLEXOELECTRIC LIQUID CRYSTALS AND THEIR APPLICATIONS." Kent State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=kent159518173259836.

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31

Guo, Jian Xin. "Chiroptical properties of Lyotropic (Acetyl)(Ethyl)cellulose liquid crystals." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39513.

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(Acetyl)(ethyl)cellulose (AEC) polymers with an ethyl degree of substitution (DS) of 2.5 and acetyl DS ranging from 0 to 0.5 form chiral nematic liquid crystals in many organic solvents. The chiroptical properties of these lyotropic AEC mesophases are extremely sensitive to the acetyl DS of AEC and the nature of the solvents although the acetyl group and solvents are achiral and all the polymers share the same chiral cellulose backbone. As the acetyl DS increases from 0 to 0.5, the pitch of AEC mesophases in a given solvent varies from a few nanometer to infinity and a reversal of handedness occurs as a compensated degree of acetylation (DA$ sp*$), where the corresponding mesophase is characterized by an infinite pitch and the absence of macroscopic chirality. The value of DA$ sp*$ and the sign of the temperature dependence of pitch depend on the solvent. Achiral dyes dissolved in these AEC mesophases display liquid crystal induced circular dichroism (LCICD), which results from the helicoidal orientation of the dyes by their chiral matrices. The sign and magnitude of the LCICD are correlated with the handedness and pitch of the AEC mesophases. The mechanism for the handedness inversion for lyotropic AEC mesophases with variation in acetyl DS is discussed.

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32

De, Luca Gino. "Computational modelling of nematic liquid crystal defects in devices and fiber processing." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103377.

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This thesis uses multiscale computational modelling to find the fundamental principles that govern defects forming during the operation of new electro-optical devices and the processing of spider silk fibers. The generalized approach developed in this thesis bridges engineering devices and biological processes based on liquid crystalline materials.
Three types of defects are encountered: inversion walls, lines and points. Inversion wall defects are found in the electro-optical device when a nematic thin film undergoes a temperature-induced surface anchoring transition. Point defects naturally occur in the tubular extrusion duct of spiders, while line defects present close topological connections with point defects and are widespread in many high-performance industrial fibers. Three models are used in this thesis and their usage is dependent on the characteristics of the defects studied.
In the case of inversion wall defects, computational modelling is used to verify, complement and analyze experimental measurements made with fluorescence confocal polarizing microscopy by our collaborator at the Georgia Institute of Technology. The various simulation results agree and explain very well experimental observations and provide a thorough understanding of the wall defects behavior. A computational technique is developed to enable the precise determination of the interaction between the liquid crystal and the device substrate. Understanding the behavior of wall defects and estimating interfacial properties are indispensable to the development and optimization of the electro-optical device as they affect properties like temperature of operation, switching voltages and response time.
Computational modelling is also used to investigate the behavior of nematic point defects confined in cylindrical cavities as observed along spiders' spinning apparatus, and to examined textural connections with other well know structures seen in industrial fibers. The various scenarios investigated include: interactions between point defects, topological transformations between point, line and ring defects as well as interactions between ring defects. The simulation results agree and complement previous investigations but also offer a new fundamental understanding on the nature and stability of defects in cylindrical cavities. Understanding the behavior of nematic point and line defects in cylindrical geometries is important as they play a fundamental role in the processing of natural and industrial high-performance fibers.

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33

Wilson, Thomas Stephen. "The rheology and structure of thermotropic liquid crystalline polymers in extensional flow." Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-05222007-091333/.

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34

Dennis, John Raymond. "Mechanisms of liquid crystal and biopolymer alignment on highly-oriented polymer thin films /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9777.

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35

Davé, Vipul. "Cellulose-based fibers from liquid crystalline solutions /." This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-08232007-112345/.

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36

Wang, Qian. "Effect of molecular order on photopolymerization behavior and polymer properties of liquid crystal monomers a dissertation /." San Antonio : UTHSC, 2008. http://proquest.umi.com.libproxy.uthscsa.edu/pqdweb?did=1594485671&sid=1&Fmt=2&clientId=70986&RQT=309&VName=PQD.

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37

Bai, Yiqun. "Structure and properties of linear and star-like thermotropic liquid crystalline polymeric fibers." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/9976.

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38

You, Seungyong. "The dynamics of DNA electrophoresis in lyotropic polymer liquid crystals." Tallahassee, Florida : Florida State University, 2009. http://etd.lib.fsu.edu/theses/available/etd-11132009-092618/.

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Thesis (Ph. D.)--Florida State University, 2009.
Advisor: David H. Van Winkle, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed on May 10, 2010). Document formatted into pages; contains xvi, 137 pages. Includes bibliographical references.

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39

Masutani, Akira. "Guest-host effect of dyes in polymer dispersed liquid crystals." Thesis, Durham University, 2002. http://etheses.dur.ac.uk/4182/.

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The guest-host [GH) effect of a tetracyanoquinodimethane (TCNQ) dye in nematic liquid crystals (LC) and polymer dispersed liquid crystals (PDLC) has been studied and compared with commercial azo and anthraquinone dyes. The adduct (MORPIP) is a conjugated molecule with a high dipole moment of 15 Debyes. E7 LC doped with MORPIP was found to give a dichroic ratio of 2.34 and an order parameter of 0.31; these values are lower than for the other dichroic dyes, typically 0.6 - 0.78. However, MORPIP showed a useful property When doped in LC and PDLC samples. The rise time of E7 was decreased by 21% when doped with 0.3 wt% MORPIP. It was suggested that MORPIP increased the dielectric anisotropy of E7 and hence reduced the rise time. Nevertheless, no change in dielectric anisotropy was observed. This observation favours a model in which the dipolar dopant reorients rapidly in the applied field and drives the reorientation of the surrounding LC The effects of the dyes incorporated in PDLGs were also studied, in order to explore their suitability for use in a colour reflective display. Dichroic PDLQ were made using the photo-initiated phase separation method. 0.37 wt7o MORPIP doped PDLCs showed a 45% faster response to an applied electric field than that of the undoped PDLCs. However, the contrast ratio of the dichroic PDLCs was not sufficiently high for display use due to insufficient scattering and dye trapping. Two new fabrication methods were developed to overcome this problem One method involved the preparation of a network type PDLC into which a doped LC was dispersed. Another method involved the preparation of voids by removing the LC from the PDLC In both methods, subsequent re-filling of the doped LC into the pre-made polymer matrix improved the contrast ratio and reduced the decay time of the dichroic PDLC

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40

Thapar, H. "Preferred orientation development in polymers." Thesis, Brunel University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384513.

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41

Biggins, John Simeon. "Soft and hard elasticity of liquid crystal elastomers." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608918.

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42

Lam, Wing Yip. "Synthesis and light emitting, liquid crystalline, and chiroptical properties of functional disubstituted polyacetylenes /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202003%20LAM.

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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.
Includes bibliographical references (leaves 308-330). Also available in electronic version. Access restricted to campus users.

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43

Wu, H. H. "Physico-chemical studies of polymers containing cycloalkyl and aza-crown-ether units." Thesis, University of Stirling, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377543.

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44

Flores, Suarez Rosaura. "Three-dimensional polarization probing in polymer ferroelectrics, polymer-dispersed liquid crystals, and polymer ferroelectrets." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2012/6017/.

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A key non-destructive technique for analysis, optimization and developing of new functional materials such as sensors, transducers, electro-optical and memory devices is presented. The Thermal-Pulse Tomography (TPT) provides high-resolution three-dimensional images of electric field and polarization distribution in a material. This thermal technique use a pulsed heating by means of focused laser light which is absorbed by opaque electrodes. The diffusion of the heat causes changes in the sample geometry, generating a short-circuit current or change in surface potential, which contains information about the spatial distribution of electric dipoles or space charges. Afterwards, a reconstruction of the internal electric field and polarization distribution in the material is possible via Scale Transformation or Regularization methods. In this way, the TPT was used for the first time to image the inhomogeneous ferroelectric switching in polymer ferroelectric films (candidates to memory devices). The results shows the typical pinning of electric dipoles in the ferroelectric polymer under study and support the previous hypotheses of a ferroelectric reversal at a grain level via nucleation and growth. In order to obtain more information about the impact of the lateral and depth resolution of the thermal techniques, the TPT and its counterpart called Focused Laser Intensity Modulation Method (FLIMM) were implemented in ferroelectric films with grid-shaped electrodes. The results from both techniques, after the data analysis with different regularization and scale methods, are in total agreement. It was also revealed a possible overestimated lateral resolution of the FLIMM and highlights the TPT method as the most efficient and reliable thermal technique. After an improvement in the optics, the Thermal-Pulse Tomography method was implemented in polymer-dispersed liquid crystals (PDLCs) films, which are used in electro-optical applications. The results indicated a possible electrostatic interaction between the COH group in the liquid crystals and the fluorinate atoms of the used ferroelectric matrix. The geometrical parameters of the LC droplets were partially reproduced as they were compared with Scanning Electron Microscopy (SEM) images. For further applications, it is suggested the use of a non-strong-ferroelectric polymer matrix. In an effort to develop new polymerferroelectrets and for optimizing their properties, new multilayer systems were inspected. The results of the TPT method showed the non-uniformity of the internal electric-field distribution in the shaped-macrodipoles and thus suggested the instability of the sample. Further investigation on multilayers ferroelectrets was suggested and the implementation of less conductive polymers layers too.
In dieser Arbeit wird eine zerstörungsfreie Technik zur Analyse, Optimierung, und Entwicklung neuer funktioneller Materialien für Sensoren, Wandler, Speicher und elektrooptische Anwendungen vorgestellt. Die Wärmepuls-Tomographie (engl. Thermal-Pulse Tomography, TPT) liefert dreidimensionale Abbildungen hoher Auflösung von elektrischen Feldern und Polarisationsverteilungen eines Materials. Bei dieser thermischen Methode wird ein fokussierter, gepulster Laserstrahl durch eine undurchsichtige Oberflächenelektrode absorbiert, welche sich dadurch aufheizt. Die einsetzende Wärmediffusion führt – aufgrund der Wärmeausdehnung des Materials – zu Änderungen der Probengeometrie, welche in pyroelektrischen Materialien einen Kurzschlussstrom oder eine Änderung des Oberflächenpotentials zur Folge hat. Diese wiederum enthalten wichtige Informationen über die räumliche Verteilung elektrischer Dipole und Raumladungen im untersuchten Material. Aus dem gemessenen Kurzsschlussstrom kann anschließend das interne elektrische Feld und die Polarisationsverteilung im Material mittels verschiedener Skalentransformations- und Regularisierungsmethoden rekonstruiert werden. Auf diese Weise ermöglichte die TPT-Methode erstmals die Darstellung inhomogener ferroelektrischer Schaltvorgänge in polymeren ferroelektrischen Filmen, welche mögliche Materialien für die Datenspeicherung sind. Die Ergebnisse zeigen eine typische Haftschicht im ferroelektrischen Polymer und unterstützen die Hypothese einer ferroelektrischen Umpolung auf einer der Korngröße äquivalenten Längenskala über Keimbildung und anschließendes Wachstum. Um die Lateral- und Tiefenauflösung zu untersuchen, wurden sowohl die TPT-Methode als auch die äquivalente Methode in der Zeitdomäne (Focused Laser Intensity Modulation Method, FLIMM) auf ferroelektrischen Filme mit Gitterelektroden angewendet. Die Ergebnisse beider Techniken zeigen nach der Datenauswertung mit unterschiedlichen Regularisierungs- und Scale-Methoden eine vollkommene Übereinstimmung. Des Weiteren stellte sich heraus, dass bisherige Untersuchungen der lateralen Auflösung von FLIMM diese möglicherweise überschätzen. Damit behauptet sich TPT als effiziente und verlässliche thermische Methode. Nach einer Optimierung der Optik wurde die TPT-Methode in polymerdispergierten Flüssigkristallen (polymer-dispersed liquid crystals, PDLC), welche in elektrooptischen Anwendungen von Interesse sind, angewendet. Die Ergebnisse deuten auf eine mögliche elektrostatischeWechselwirkung zwischen den COH-Gruppen des Flüssigkristalls und den Fluoratomen der verwendeten ferroelektrischen Matrix hin. Die durch rasterelektronenmikroskopische Aufnahmen (scanning electron microscopy, SEM) gewonnenen geometrischen Parameter der Flüssigkristalltröpfchen konnten mittels TPT reproduziert werden. Für weitere Anwendungen werden schwach ferroelektrische Polymermatrices vorgeschlagen. Im Bestreben neue polymere Ferroelektrete zu entwickeln und deren Eigenschaften zu optimieren, wurden neuartige Mehrschichtsysteme untersucht. Die Ergebnisse aus der TPT-Methode zeigen eine Abweichung der Uniformität der inneren Verteilung des elektrischen Feldes in den geformten Makrodipolen, was auf eine Instabilität der Probe hindeutet. Ebenfalls wurden weitere Untersuchungen an Mehrschicht-Ferroelektreten und die Anwendung von halbleitenden Polymerschichten vorgeschlagen.

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45

Daga, Kamal Dhulchand. "Extrusion of a thermotropic liquid crystal polymer." Ohio : Ohio University, 1987. http://www.ohiolink.edu/etd/view.cgi?ohiou1183043184.

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46

Jacob, Sunny. "Synthesis and characterization of low-melting thermotropic liquid crystalline poly(ester-imide)s /." Online version of thesis, 1994. http://hdl.handle.net/1850/11881.

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47

Fan, Yun-Hsing. "TUNABLE LIQUID CRYSTAL PHOTONIC DEVICES." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3926.

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Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices and their fabrication methods. The devices presented include inhomogeneous polymer-dispersed liquid crystal (PDLC), polymer network liquid crystals (PNLC) and phase-separated composite film (PSCOF). Liquid crystal/polymer composites could exist in different forms depending on the fabrication conditions. In Chap. 3, we demonstrate a novel nanoscale PDLC device that has inhomogeneous droplet size distribution. In such a PDLC, the inhomogeneous droplet size distribution is obtained by exposing the LC/monomer with a non-uniform ultraviolet (UV) light. An electrically tunable-efficiency Fresnel lens is devised for the first time using nanoscale PDLC. The tunable Fresnel lens is very desirable to eliminate the need of external spatial light modulator. Different gradient profiles are obtained by using different photomasks. The nanoscale LC droplets are randomly distributed within the polymer matrix, so that the devices are polarization independent and exhibit a fast response time. Because of the small droplet sizes, the operating voltage is higher than 100 Vrms. To lower the driving voltage, in Chap. 2 and Chap. 3, we have investigated a polymer-network liquid crystal (PNLC) using a rod-like monomer structure. Since the monomer concentration is only about 5%, the operating voltage is below 10 Vrms. The PNLC devices are polarization dependent. To overcome this shortcoming, stacking two cells with orthogonal alignment directions is a possibility. In Chap. 3, another approach to lower the operating voltage is to use phase-separated composite film (PSCOF) where the LC and polymer are separated completely to form two layers. Without multi-domain formed in the LC cell, PSCOF is free from light scattering. Using PNLC and PSCOF, we also demonstrated LC blazed grating and Fresnel lens. The diffraction efficiency of these devices is continuously controlled by the electric field. Besides Fresnel lens, another critical need for imaging and display is to develop a system with continuously tunable focal length. A conventional zooming system controls the lens distance by mechanical motion along the optical axis. This mechanical zooming system is bulky and power hungry. To overcome the bulkiness, in Chap. 4 we developed an electrically tunable-focus flat LC spherical lens which consists of a spherical electrode imbedded in the top flat substrates while a planar electrode on the bottom substrate. The electric field from the spherical and planar electrodes induces a centrosymmetric gradient refractive index distribution within the LC layer which, in turn, causes the focusing effect. The focal length is tunable by the applied voltage. A tunable range from 0.6 m to infinity is achieved. Microlens array is an attractive device for optical communications and projection displays. In Chap. 5, we describe a LC microlens array whose focal length can be switched from positive to negative or vise versa by the applied voltage. The top spherical electrode glass substrate is flattened with a polymer layer. The top convex substrate and LC layer work together like a zoom lens. By tuning the refractive index profile of the LC layer, the focal length of the microlens array can be switched from positive to negative or vise versa. The tunable LC microlens array would be a great replacement of a conventional microlens array which can be moved by mechanical elements. The fast response time feature of our LC microlens array will be very helpful in developing 3-D animated images. A special feature for LC/polymer composites is light scattering. The concept is analogous to the light scattering of clouds which consist of water droplets. In Chap. 6, we demonstrate polymer network liquid crystals for switchable polarizers and optical shutters. The PNLC can present anisotropic or isotropic light scattering behavior depending on the fabrication methods. The use of dual-frequency liquid crystal and special driving scheme leads to a sub-millisecond response time. The applications for display, light shutters, and switchable windows are emphasized. Although polymer networks help to reduce liquid crystal response time, they tend to scatter light. In Chap. 7, for the first time, we demonstrate a fast-response and scattering-free homogeneously-aligned PNLC light modulator. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. As a result, the PNLC response time is ~300X faster than that of a pure LC mixture except that the threshold voltage is increased by ~25X. The PNLC cell also holds promise for mid and long infrared applications where response time is a critical issue.
Ph.D.
Other
Optics and Photonics
Optics

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48

Weng, Libo. "Polymer Stabilized Liquid Crystals: Topology-Mediated Electro-Optical Behavior And Applications." Kent State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=kent1460763169.

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49

López, Betty Lucy. "Thermophysical and Mechanical Properties of Polymer Liquid Crystals and Their Blends." Thesis, University of North Texas, 1994. https://digital.library.unt.edu/ark:/67531/metadc278308/.

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Tensile properties, namely the elastic modulus, tensile strength, percent of elongation at yield and at the break were determined for the pure components and blends. The results are connected to the respective phase diagrams and demonstrate that blending makes property manipulation possible. Blends for which the mechanical properties are better than those of pure EPs can be obtained.

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Pople, John. "Organized structures induced in polymeric and liquid crystalline systems by shear deformation." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308051.

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