Dissertations / Theses: 'POLYMERS; LIQUID CRYSTALS'

1

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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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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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

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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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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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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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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8

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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9

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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10

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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11

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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12

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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13

Bagheri-Hamaneh, Mehdi. "Theory, Modeling, and Simulation of Liquid Crystals and Polymers." Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1143821571.

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14

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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15

Elliott, Alice Margaret Sophie. "The physical structure of a system of mesogenic side chain polymers." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388435.

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16

Sarnecki, Greg. "Studies in soluble conjugated polymers." Thesis, University of Cambridge, 1994. https://www.repository.cam.ac.uk/handle/1810/272769.

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17

Christie, David W. "Alternating copolymers containing side-chain liquid crystal groups." Thesis, University of Aberdeen, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311158.

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The copolymerisation of N-ethyl maleimide (NEM) with ethyl vinyl ether (EVE) in benzene (Bz) was investigated. The copolymerisation displays a tendency towards alternation but is not alternating and propagation involves the formation of a 1:1 NEM/EVE charge-transfer complex. This complex and the monomer/solvent complexes were investigated by ¹H NMR spectroscopic methods. The equilibria were combined mathematically to model the NEM/EVE/Bz system. The copolymerisations of functionalised N-substituted maleimides, N-4-[6-(4'-methoxy-4-azobenzoxy) hexoxycarbonyl] phenylmaleimide (NMeAz6PM) and N-4-[6-(4'-nitro-4-azobenzoxy)hexoxycarbonyl] phenylmaleimide (NNitAz6PM), with styrene (St), 4-vinyl pyridine (4VP), or EVE as the comonomer were studied and the reactivity ratios calculated. The monomer pairs NMeAz6PM/St, NMeAz6PM/4VP and NNitAz6PM/St produce alternating copolymers but NMeAz6PM/EVE does not. The absence of liquid crystallinity in these materials was attributed to the rigidity of the polymer backbone coupled with the low mesogen content arising from the alternating backbone. Blends of amorphous maleimide based copolymers with 6-(4-methoxy-4'-azobenzoxy)hexanoic acid, 4.2, were investigated. The copolymers chosen were believed to be alternating and are the product of the copolymerisation of N-phenyl, N-(4-methoxy) phenyl, or N-(4-hydroxy) phenyl maleimide with St or 4VP. 4.2 is essentially immiscible with the St based copolymers. However 4.2 is miscible with the 4VP based copolymers and liquid crystallinity is induced. This behaviour is attributed to the formation of hydrogen bonds between 4.2 and the pyridyl units of the copolymer backbone. Blends of 4.2 or 6-(4-nitro-4'azobenzoxy)hexanoic acid, 5.2, with copoly(NMeAz6PM-alt-St) or copoly(NMeAz6PM-alt-4VP) were investigated. The limited miscibility and liquid crystalline behaviour of the acid/styrene copolymer blends was attributed to interactions between the mesogens on the copolymer and the acid. However, the enhanced miscibility and liquid crystalline behaviour seen in the pyridine blends can be attributed to the formation of hydrogen bonds between the acids and the pyridyl units of the backbone, in addition to the acid/copolymer mesogen interactions.

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18

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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19

Callan, John Francis. "Low molecular mass and polymeric liquid crystals containing sulphur." Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301776.

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20

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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21

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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22

Avant, Lavern Marshall. "Synthesis and characterization of a cross-digitated poly (2,5-Benzoxazole) (ABPBO)." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/8464.

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23

Keates, P. A. "The development of organized structure in cellulose derivatives." Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384910.

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24

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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25

Ahn, Sangbum. "Synthesis and Functionalities of Conjugated Polymers with Controllable Chirality and Low Bandgaps." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199335.

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26

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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27

Simoes, Ricardo J. F. "Mechanical behavior and performance of injection molded semi-crystalline polymers." Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc5528/.

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I have used computer simulations to investigate the behavior of polymeric materials at the molecular level. The simulations were performed using the molecular dynamics method with Lennard-Jones potentials defining the interactions between particles in the system. Significant effort was put into the creation of realistic materials on the computer. For this purpose, an algorithm was developed based on the step-wise polymerization process. The resulting computer-generated materials (CGMs) exhibit several features of real materials, such as molecular weight distribution and presence of chain entanglements. The effect of the addition of a liquid crystalline (LC) phase to the flexible matrix was also studied. The concentration and distribution of the second phase (2P) were found to influence the mechanical and tribological properties of the CGMs. The size of the 2P agglomerates was found to have negligible influence on the properties within the studied range. Moreover, although the 2P reinforcement increases the modulus, it favors crack formation and propagation. Regions of high LC concentration exhibit high probability of becoming part of the crack propagation path. Simulations of the tensile deformation under a uniaxial force have shown that the molecular deformation mechanisms developing in the material depend on several variables, such as the magnitude of the force, the force increase rate, and the level of orientation of the chains. Three-dimensional (3D) graphical visualization tools were developed for representation and analysis of the simulation results. These also present interesting educational possibilities. Computer simulations provide us information which is inaccessible experimentally. From the concomitant use of simulations and experiments, a better understanding of the molecular phenomena that take place during deformation of polymers has been established.

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28

Lau, Richard Yiu-Ting. "Surface segregation of amorphous, semi-crystalline and liquid crystalline polymers /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CENG%202006%20LAUR.

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Wu, Jiawei. "Physical Properties of Blends of Triblock Copolymer (SEBS) with Low Molar Mass Liquid Crystals." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1434368185.

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30

KUO, THAU-MING. "SYNTHESIS AND CHARACTERIZATION OF MONOMERS AND POLYMERS CONTAINING MULTIPLE P-ARYLENEAZO OR P-BENZOQUINODIIMINE GROUPS: CONDUCTING POLYMERS, LIQUID CRYSTAL POLYMERS, AND DIPOLAR POLYMERS." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184215.

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Aniline Black, a polymer containing p-benzoquinodiimine groups, was synthesized chemically or electrochemically by the oxidation of aniline. The polymer salts showed the conductivity of 10⁻¹-10⁻³ ohm⁻¹cm⁻¹. Polymers containing anthroquinodiimine units were also prepared by polycondensations. The syntheses of model compounds containing p-benzoquinodiimine were attempted. Multiazobisphenol monomers were synthesized. 4,4'-(3,3'-Dimethyl-4,4'-biphenylenebisazo) bisphenol 7, 4,4'-[azobis(p-phenyleneazo)] bisphenol 8, and 4,4'-(2-methoxy-1,4-phenylenebisazo) bisphenol 10 displayed liquid crystal (l.c.) properties, while model derivatives of 7, 8, and 4,4'-(4,4'-stilbenebisazo) bisphenol 9 did likewise. Monomers and derivatives of 4-[(4-hydroxyphenyl)azo]-1-naphthol 5, and 4,4'- [oxybis(p-phenyleneazo)] bisphenol 6 showed no l.c. behavior. New thermotropic polyesters based on these multiazobisphenols were synthesized. Sebacates of 5, 6, 7, 8, and 10 showed l.c. behavior, while polymers based on isophthalic or 5-t-butylisophthalic acid did not do so. Polyformals were also synthesized from these momoners, only that of 4 showed weak l.c. behavior. The correlation between the structure of these polymers and their tractabilities, electrical properties, liquid crystal behaviors was studied. Polymers and copolymers containing p-azoarylene and p-azoxyarylene groups were synthesized by oxidative coupling of various aromatic diamines. Films were cast directly from the reaction mixtures or from the polymer solution. The films were n-doped by sodium naphthalide or p-doped by iodine. They showed electrical conductivities of 10⁻⁴ to 10⁻⁵ ohm⁻¹cm⁻¹. AB monomers containing dipolar p-phenyleneazo groups were synthesized: 4-(4-hydroxy-2-methoxyphenylazo) benzoic acid 21, 4-[4-(4-hydroxy-2-methoxyphenylazo)-2-methoxyphenylazo] benzoic acid 22, and 4-(4-hydroxy-2-methoxyphenylazo)-3-nitrobenzoic acid 23. The monomers were polymerized by direct polycondensations. The polyester synthesized from 21 formed a red, transparent film. A polymethacrylate containing dipolar p-phenyleneazo groups in the side chains was also prepared by the free radical polymerization of 1- [3-methoxy-4-(p-nitrophenylazo)-phenoxy] hexyl methacrylate 28.

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31

Rai, Kashma K. Fontecchio Adam. "Study of spectral sensing using electro-optic films /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3274.

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32

Millan, Barrios Enrique Jose. "Synthesis and electrochemistry of pyrrole derivatives." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242418.

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33

McKenzie, Blayne M. "Metallo-Responsive Liquid Crystalline Monomers, Polymers and Networks." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1295565872.

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34

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

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35

Chuah, Siew Peng. "In-situ fibre formation & management of thermotropic liquid crystalline polymers in thermoplastic matrices." Thesis, Brunel University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295188.

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36

Done, Dinshong. "Studies on the rheology and morphology of thermotropic liquid crystalline polymers." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/77792.

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It is known that the physical properties of as-processed liquid crystalline polymers are highly dependent on the thermal and deformation histories of the materials experienced. The purpose of this study has been to examine the effect of thermal history on the rheology and morphological texture for several thermotropic liquid crystalline polymers. These include two copolyesters of para-hydroxybenzoic acid and polyethylene terephthalate and a copolymer of para-hydroxy benzoic acid and 6-hydroxy-2-naphthoic acid. For all three systems, it was found that the viscosities at temperatures below the normal flow temperatures were reduced as a result of preheating. Furthermore, these polymers were able to flow at temperatures as much - as 50°C below their normal flow temperatures if preheated and cooled rapidly. Also found was that it took a few minutes for the viscosities of the preheated samples to recover to a higher level at which the flow was ceased, during this period the materials were processable. These behaviors were attributed to the supercooling of the nematic state formed at preheating temperatures. This was supported by the lack of transition peaks in DSC traces obtained under the same cooling history as that in the Rheometric Mechanical Spectrometer. In the cold die extrusion experiment, a skin/core structure was observed for most extrudates. The thickness of the skin layer was directly related to the orientation and tensile properties of the extrudate. The thicker the skin layer was, the better the orientation and tensile properties were. The thickness of the skin layer was also found to increase with the extrusion speed. However, the orientation was only limited to the skin layer with the core region was relatively unoriented. For the lubricated squeezing flow experiments, the newly designed device worked satisfactory and predicted the relationship that the transient biaxial extensional viscosities are very close to six times the transient shear viscosities for polystyrene at small strains. Loss of lubrication occurred at fairly low strains, 0.3 to 0.4, was the limit of this method. For all three liquid crystalline polymers, the transient biaxial extensional viscosity was found to decrease with the increase in squeezing rate and no steady state was reached. Yield stresses were observed for liquid crystalline polymers under the squeezing jump strain deformation and the magnitude of these yield stresses were of the order of several hundreds Pa. The existence of yield stresses could be due to the presence of some structure in the sample which prevented the stress from relaxing to zero. The constant stress lubricated squeezing flow method has been proved to not be suitable for estimating the biaxial extensional viscosity of liquid crystalline polymers because the constant slope region for the creep curve was too short and it was difficult to determine the extension rate accurately. Under a heavy stress of 70368 Pa and proper cooling, it was possible to generate some fibrous structure in the squeezed sample.
Ph. D.

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37

Kalakonda, Parvathalu. "Thermal Physical Properties Of Nanocomposites Of Complex Fluids." Digital WPI, 2013. https://digitalcommons.wpi.edu/etd-dissertations/301.

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"Composites of nanoparticles with complex fluids represent a unique physical system where thermal physical properties of the components partially or fully mix and new behavior can emerge. Traditional composites are relatively well understood as the superposition, weighted by volume or mass, of the components properties and the interfacial interactions play the role of holding the composite together. As the filler component, nanoparticle, decreases in size, the surface area begins to dominate, leading to unique behavior of the nanocomposites. The richness of the nanocomposites that can be designed by coupling various nanoparticles and complex fluid materials opens a wide field of active research. This dissertation presents a series of experimental studies on various nanocomposites using modulated differential scanning calorimetry, spectroscopic ellipsometry, dielectric spectroscopy, polarizing microscopy, and conductivity measurements of nanoparticles such as multi-wall carbon nanotubes and quantum dots on the phase transitions of several liquid crystals and polymers. The liquid crystals (LCs) and liquid crystalline polymer (LCP) of interest are: negative dielectric anisotropy alkoxyphenylbenzoate (9OO4), octylcyanobiphenyl (8CB), decylcyanobiphenyl (10CB), and isotactic polypropylene (iPP) which can form smectic liquid crystal (LC) phase. Studies have been carried out as a function of concentration and temperature spanning through various ordered phases. The results indicate a mixture of ordering and disordering effects of the nanoparticles on the phases of the complex fluids. In 9OO4/CNT system, dipole moment of liquid crystal and graphene like surface can allow a random dispersion of CNT to promote both orientational and positional order. For nCB/CNT, nCB/Quantum dot (QD) systems, nanoparticles induce net disordering effect in LC media. The effect of QDs on LC depends on the anchoring conditions and the QDs size. The results clearly demonstrate that the nematic phase imposes self-assembly on QDs to form one dimensional arrays. This leads to net disordering effect. The thermal/electrical conductivity changes in thin films of iPP/CNT sheared/un-sheared samples and it also varies with temperature for the purpose of inducing anisotropy of those properties in parallel and perpendicular to average orientation. The percolation threshold is clearly pronounced in both conductivities due to pressing and shearing treatment of the films. This will further our abilities to nano-engineer material for many important applications."

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38

Linegar, Kirtland L. "Applications of dynamic light scattering in chemical engineering polymers, proteins, and liquid crystals /." College Park, Md. : University of Maryland, 2008. http://hdl.handle.net/1903/8314.

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Thesis (M.S.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Institute for Physical Science and Technology & Dept. of Chemical and Biomolecular Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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39

Georgiev, Georgi Yordanov. "Structural studies of polymers and polymer liquid crystals by X-ray scattering, thermal analysis and ellipsometric studies through polarized light microscopy /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2002.

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Thesis (Ph.D.)--Tufts University, 2002.
Adviser: Peggy Cebe. Submitted to the Dept. of Physics. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

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40

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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41

Kulkarni, Rahul. "Unique Morphology and Structure of New Organic Porphyrin Based Discotic Liquid Crystals." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1271041395.

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42

Echeverri, Mauricio. "Phase Diagram Approach to Fabricating Electro-Active Flexible Films: Highly Conductive, Stretchable Polymeric Solid Electrolytes and Cholesteric Liquid Crystal Flexible Displays." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1352949368.

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43

Blizard, Kent G. "A morphological investigation of polymer blends of two engineering thermoplastics with a liquid crystalline copolyester." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/63970.

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44

Ritcey, Anna Marie. "Chiroptical properties of cellulose derivatives." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75758.

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The chiroptical properties of isotropic solutions, cholesteric liquid crystals and solid films prepared from selected cellulose derivatives are investigated by optical rotary dispersion (ORD) and circular dichroism (CD). Optical activity from intrinsic molecular dissymmetry, polymer conformation and cholesteric reflection properties are considered.
The chiroptical properties of cholesteric liquid crystals are interpreted according to deVries' theory. Lyotropic liquid crystalline phases formed by (hydroxypropyl)cellulose in methanol display anomalously high optical rotation at low wavelengths. The anomalies disappear on the addition of a dipolar aprotic solvent, and are absent for the ethyl ether derivative of the polymer, indicating a chiral hydrogen bonded structure is contributing to the optical activity.
Investigation of the chiroptical properties of cellulosics by circular dichroism requires the presence of a suitable chromophore, either as a chain substituent or as an added dye. Congo red exhibits induced optical activity in dilute aqueous solutions of methylcellulose and cellulose oligomers, providing evidence for the presence of a helical conformation. CD spectra of two new biphenyl derivatives also exhibit exciton splitting characteristic of a helical arrangement of chromophores. Conformational dissymmetry is not indicated in spectra of cellulose acetate although the sign of carbonyl CD band is solvent dependent. The sign of this band is interpreted in terms of the orientation of the ester substituent relative to the anhydroglucose ring. Congo red, bound in cholesteric cellulose films prepared by the deacetylation of cellulose acetate cast from mesophase solution, shows induced optical activity which, in this case, reflects the cholesteric nature of the matrix. Similar results for cellulose gels regenerated from LiCl/N,N-dimethylacetamide solution indicate that cellulose adopts a supramolecular helicoidal arrangement on slow precipitation from solution.
The optical properties of the thermotropic cholesteric liquid crystalline phase formed by a new cellulose derivative, (ethoxypropyl)cellulose, are examined by circular reflectivity measurements.
The cholesteric reflection properties of mesophase solutions of cellulose acetate in trifluoroacetic acid are characterized. The polymer undergoes rapid trifluoroacetylation in this solvent and the presence of trifluoroacetate substituents alters the handedness and the magnitude of the pitch. Although the pitch is sensitive to the nature of achiral substituents, it is not influenced by the addition of chiral solvents. (Abstract shortened with permission of author.)

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45

Viola, Georg Giuseppe. "Rheological characterizaton, and the development of molecular orientation and texture during flow for a liquid crystalline copolymer of para- hydroxybenzoic acid and polyethylene terephthalate." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/49953.

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Abstract:

It is generally agreed that the high physical properties arising in as-processed liquid crystalline materials are due to the high degree of molecular orientation which develops during the processing step. In order to more fully understand and predict such behavior, a constitutive equation describing the flow behavior of these materials would be useful. It has been suggested that in order to describe the rheology of liquid crystalline fluids such a constitutive equation would need to include molecular orientation effects. The purpose of part of this study has been to examine the usefulness of several constitutive equations for describing the steady and transient behavior of several liquid crystalline polymers. These include a copolyester of para-hydroxybenzoic acid and polyethylene terephthalate, and an anisotropic solution of 12 weight% Kevlar in 100% sulfuric acid. It was found that in the case of the copolyester system, the steady shear and dynamic viscosities were equal over certain temperature ranges. For this reason, the constitutive equation of Zaremba, Fromm, and DeWhitt (ZFD model) was used to predict the steady state behavior of the system studied. From knowledge of either the steady shear or dynamic viscosity it was possible to predict both the steady state normal stresses (N1) and the storage modulus (G'). The model could not, however, predict the transient behavior of the systems studied. Ericksen’s anisotropic fluid theory has been investigated in detail as it takes molecular orientation effects into account. Ericksen’s theory can partially explain the transient behavior of the systems studied in terms of molecular orientation which develops during shear flow. However, wide angle x-ray scattering (WAXS) and scanning electron microscope (SEM) studies reveal that shear flow has little effect on the development of molecular orientation during flow. In addition, any orientation produced during flow may be lost within thirty seconds at the melt temperature. It appears that a disruption of texture is occurring during flow which may need to be incorporated into the theory of Ericksen.
Ph. D.
incomplete_metadata

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46

Evans, Stacy Alexandria Banford. "Dithiafulvene (1,3-dithiole) and acrylate liquid crystals: Synthesis of monomers and polymers with possible electronic and electro-optic applications, and investigations in the synthesis of pure (meth)acrylates." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184777.

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Abstract:

In this work, using the idea of an electrically conducting "functional unit," monomers and polymers with possible electronic and electro-optic applications were synthesized. The synthesis and polymerizations were, in many cases, novel and non-trivial. Dithiafulvene (1,3-dithiole) and variations of this functional unit were synthesized and incorporated into new condensation polymers. Polyesters, polyamides and polyhydrazones were all successfully synthesized and could be cast into films. These new polymers might be applicable as processable conducting materials if compatible dopants are employed or by themselves in the area of third order non-linear optics. Using a (meth)acrylate backbone, a spacer group of six methylene units, and a phenyl-CO₂-phenyl mesogen, linked by an ester group to a strongly polar optically active center containing a methoxy group, three new novel monomers and polymers were designed to exhibit smectic C* liquid-crystal phases. The polymers exhibited liquid crystalline behavior as was shown in differential scanning calorimetry and optical microscopy. Further studies and investigations in the synthesis of pure (meth)acrylate esters and their homopolymers yielded surprising results with regard to the Schotten-Baumann reaction. Interestingly, the use of meth(acryloyl) chloride in this scheme leads to (meth)acrylic anhydride, which is not easily isolable from distillable products. This anhydride is responsible for gelation in the polymerization of glycolate esters, and cannot be removed by work-up with various nucleophiles without disrupting desired ester functions. An S(N)2 method is recommended in this work.

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47

Ko, Chan Uk. "Studies of blends containing liquid crystalline polymers with PET and related investigations of hydroquinone/biphenol polysulfone systems." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/76036.

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Abstract:

The investigation of structure-property behavior of extruded cast films prepared from blends of thermotropic liquid crystalline copolyesters with polyethylene terephthalate (PET). Data were obtained which showed not only the temperature dependence of the moduli and stress-strain behavior but also the orientation effects that must be prevalent in order to explain the differences between the moduli measured parallel and perpendicular to the extrusion direction. Only at high liquid crystal polymer (LCP) compositions is the modulus particularly increased. The modulus enhancement with lower LCP content and utilization of process variables are discussed. Specifically, the extruder gear pump speed did not enhance Young's modulus at the same LCP content as extensively as did the effect of extruder screw speed. Also a study to synthesize and characterize new segmented copolymers that could produce unusual film properties are discussed. The approach involved the synthesis of high Tg (220 C) isotropic poly (aryl ether sulfone) oligomers of varying segment molecular weights. The thermal and mechanical studies of the copolymers have been carried out to probe the potential of these copolymers for signs of liquid crystalline character and to note their ability to thermally crystallize as well as to crystallize by solvent or strain inducement. Along these lines, thermal analysis, polarizing hot-stage microscopy, wide angle x-ray scattering and mechanical testing were utilized in this investigation
Master of Science

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48

Handlos, Agnita A. "The processing of microcomposites based on polypropylene and two thermotropic liquid crystalline polymers in injection molding, sheet extrusion, and extrusion blow molding." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-164735/.

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49

Lau, Richard Yiu-Ting. "Study of surfaces of semi-crystalline polymers by static time-of-flight secondary ion mass spectrometry /." View abstract or full-text, 2010. http://library.ust.hk/cgi/db/thesis.pl?CBME%202010%20LAU.

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50

Morris, Christopher J. "Capillary-force driven self-assembly of silicon microstructures /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/5963.

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Dissertations / Theses on the topic 'POLYMERS; LIQUID CRYSTALS'

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