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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

The study of structure and dynamics in organometallic compounds

Stevenson, Maya January 1998 (has links)
No description available.
22

Synthesis of multi-Functional Discotic Liquid Crystal Dimers

Tzeng, Mei-chun 12 September 2006 (has links)
The scarcity of research about nitrogen containing heterocyclic discotic liquid crystal has made it an interesting subject for chemists. In this thesis, we will discuss the synthesis and properties of four kinds of new dimeric discotic liquid crystal in details. The first type of new dimeric discotic liquid crystals were synthesized based on a novel core structure, dibenzo[a,c]phenazine. All dimers linked by a hexyl-chain spacer exhibited columar phase. The range of mesomorphic temperature became wide as the chain length of spacer increased. Simultaneously, we also changed terminal chain length to investigate the influence on mesomorphic properties by attached terminal group. The second type of new dimeric discotic liquid crystals, which contained the dibenzoquinoxaline skeleton, didn¡¦t show the properties of mesomorphic phase due to the poverty of planality. The third type of molecules, which also have the dibenzoquinoxaline skeleton, were the banana-shaped discotic liquid crystals. We anticipated these dimeric molecules would demonstrate another special mesogenic phase. The last type of dimeric discotic liquid crystals were the extension of our previously research. These molecules, which comprised 5,6,11,12,17,18- hexaazatrinaphthylene skeleton, would be good candidates for using as a n-type material.
23

Organic semiconductor co-crystals: reactivity, mobility, and spectroscopy

Sumrak, Joseph Charles 01 July 2011 (has links)
Organic semiconductors are of interest because low processing temperatures and cost which make such materials candidates for flexible electronics. The charge transport properties of the material are largely dependent on solid-state arrangement of the molecules. This thesis focuses on co-crystallization as a means to achieve [2+2] photodimerization with organic semiconductors, the impact the co-crystal former has on mobility, the use of a co-crystal former to obtain different conformations of a flexible system, and the ability to detect the change in conformation by infrared spectroscopy. [2+2] photodimerization is studied as a way to alter the orientation of the π-systems in the solid state. To align a semiconductor building block into an orientation suitable for [2+2] photodimerization a co-crystallization method was used. The result of the photoreaction is the formation of a dimer in which the π-systems of the semiconductor building block are in a different orientation then before. Changes in the physical properties of the material through photodimerization are explored as a method for patterning thin films. The impact the second component has on the overall mobility in our system is examined. The second component is not expected to act as a semiconductor and the impact on mobility the by its inclusion in the solid is unknown. The impact of a second component on mobility is studied by observing the mobility of multiple co-crystals along with the mobility of the single component. It was found that the mobility could be increased by a factor of approximately 200 with addition of a second component. The mobility change seen in the two-component crystals is equated to the changes observed in the crystal packing. The conformation a molecule adopts in a solid can vary. It was discovered that the addition of a second component can be used to select the major conformation a bithiophene adopts in a solid. The change in conformation changes the orientation of the π-systems between molecules within the solid. The ability for a second component to alter the conformation of a bithiophene is explored. Infrared spectroscopy is used as a facial method to detect the change in the bithiophene conformation.
24

The investigation of optically tunable blue phase doped with azobenzene

Liu, Hu-Yi 02 July 2010 (has links)
This study presents an optically switchable band gap of a 3D photonic crystal that is based on an azobenzene-doped liquid crystal blue phase. The trans-cis photoisomerization of azobenzene was induced by irradiation using 473nm light, and caused the deformation of the cubic unit cell of the blue phase and a shift in the photonic band gap. The fast back-isomerization of azobenzene was induced by irradiation with 532nm light. The crystalline structure was verified using a Kossel diffraction diagram. An optically addressable blue phase display, based on Bragg reflection from the photonic band gap, is also demonstrated. It can be written, erased, and rewritten repeatedly and exhibits a bright saturated color.
25

Band-Structure Analysis of Liquid-Crystal Photonic Crystal Fibers

Kao, Chia-Lung 23 July 2009 (has links)
Filling the liquid crystals (LCs) into the air holes of the photonic crystal fibers (PCFs), we can obtain the liquid-crystal photonic crystal fibers (LCPCFs). Due to the tunable optical properties of the LCs, we can fabricate tunable optical devices based on the LCPCFs. In this thesis, we investigate the photonic bandgap (PBG) properties and find out the effective modal index curves of the LCPCFs by the finite-difference frequency-domain (FDFD) method. The effects of the operation temperature and the alignment of the LCs are discussed. When the alignment of the LC is in the transverse plane of the PCF, we can observe the blue shift and the splitting of the PBGs as we increase the operation temperature. As the LC is aligned along the PCF, the red shift occurs and the splitting disappears. The shift and the splitting of the PBGs are due to the high anisotropic property of the LCs. Besides, we can rotate the alignment of the LCs by the external electric field, and the effects of the alignment on the propagation properties of the LCPCFs are larger than those of the operation temperature. In the experiment, we successfully fabricate the LCPCFs by using the vacuum method. In the measurement of the LCPCF at different operation temperatures,the red shift of the spectra can be observed with the increasing operation temperatures, which has a very good agreement with the simulation results. As we vary the alignment of the LCs with the external electric field, the transmission bands are almost the same as the voltage is less than 200V. During the range of 200V to 400V, the PBGs demonstrate obvious variations and the deep appears at 1050nm. When the external electric field is raised to 400V, the shapes of the spectra are almost the same and the red shift of the PBGs can be observed. The results of our simulation and the experiment measurement can help us to design and fabricate optical devices based on the LCPCFs.
26

Synthesis of New Dibenzo[a,c]phenazine Discotic Liquid Crystal (II)

Hsu, Jan-teng 24 August 2009 (has links)
Because of the unique physical properties of liquid crystal molecules, such as: light, electricity, magnetic anisotropy, they exhibit different values, the most known current application on displays in our life. As the liquid crystal molecules can be modified through the functional groups, thereby affecting its physical properties, it caused great interests in synthetic chemists. In this thesis, we synthesized liquid crystal based on dibezo[a,c]phenazine core and the dioxole skeleton was also induced into dove-tail alkyl chain functional group surrounding the central aromatic core . Moreover, we also change the chain length of alkyl chain to explore stacking arrangement structure of the mesophase. By the various instruments to explore the nature of stacking, we preliminary assumed that the mesophase might exhibit the helical stacking with excellent charge mobility, which could be good candidates for optical and electrical applications.
27

Multimedia video interface controller for silicon microdisplay application /

Cheung, Hon Lung. January 2002 (has links)
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves [61]-[65]). Also available in electronic version. Access restricted to campus users.
28

Design and development of liquid crystal lenses

Ashraf, Mujahid Al Islam. January 2006 (has links)
Thesis (MEng) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Micro-Photonics, 2006. / A thesis submitted for the degree of Master of Engineering, Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2006. Typescript. Includes bibliographical references (p. 74-77).
29

Processing, characterizations and optical modeling of color filter liquid-crystal-on-silicon microdisplays /

Zhang, Baolong. January 2006 (has links)
Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.
30

Mechanically stabilized bistable FLCD on flexible substrates /

Au, Ping Tong. January 2006 (has links)
Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 106-110). Also available in electronic version.

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