No description available.

The principal aim of this Thesis is the synthesis and characterisation of a range of novel liquid crystals designed to exhibit the twist-bend nematic phase (NTB), in order to enhance our understanding of the relationships between molecular structure and the observation of NTB behaviour. Moreover, the inclusion of chiral fragments allowed the effects of molecular chirality on the structure of the NTB phase, specifically the chiral twist-bend nematic phase, N*TB, to be studied. In Chapter 3, a series of non-symmetric odd-membered liquid crystal dimers are prepared and the terminal chain length m is varied. A change in the local molecular structure from intercalated to bilayer is seen on increasing m, but this has no apparent effect on the stability of both the nematic and twist-bend nematic phases, which show a regular dependence on m. A novel twist-bend smectic phase is reported. Chapter 4 investigates the effects of branching this terminal chain on phase behaviour. It is evident that in dimers with a shorter spacer, branching destabilises the N and NTB phases while stabilising smectic behaviour, but in longer homologues smectic behaviour is also destabilised. Chapter 5 explores the effect of molecular bulk on phase behaviour, specifically the stability of the NTB phase, by the incorporation of a pyrene moiety. This group supresses crystallisation such that stable, low temperature NTB phases are formed despite the bulky group. Chapters 6 and 7 study the inclusion of chiral moieties in bent-shaped, odd-membered dimers: specifically, 2-methylbutyl, 1-methylheptyl (6) and lactic esters (7). New examples of the rarely observed chiral twist-bend nematic phase are seen. Phase behaviour is investigated and compared to achiral and racemic analogues. Chapter 8 describes the mesogenic behaviour of molecular complexes assembled by hydrogen bonding between both achiral and chiral stilbazole-based and benzoic acid-based fragments. A selection of the complexes exhibit the N(*)TB phase despite only one or neither component being mesogenic.

Foram estudadas as seguintes mesofases liotrópicas tipo I, que se orientam espontaneamente em presença de campo magnético, com o eixo de simetria paralelo ao campo: laurato de potássio/KCl/H2O e decilsulfato de césio/CsNO3/H2O; foi estudada também a mesofase liotrópica laurato de potássio/H2O, que não apresenta a propriedade de orientação magnética espontânea. Foram utilizadas as técnicas da difração de raios-X em alto e baixo ângulos e, de forma acessória, microscopia óptica de luz polarizada, calorimetria diferencial de varredura e criofratura( freeze etching). A mesofases foram acondicionadas em diferentes tipos de porta-amostras com e sem tratamento químico de superfície, submetidas a campos magnético e elétrico, bem como a variações de temperatura. Esse estudo possibilitou a identificação de geometria das unidades difratoras, confirmando o modelo de micelas cilíndricas, para o tipo I, bem como forneceu evidências da influência dos efeitos de superfície e da formação de agregados de micelas com dimensões variadas, que originaram os padrões de difração. Foi confirmada a coexistência das fases hexagonal infinita e tipo I em equilíbrio termodinâmico. Foi construído um modelo de agregados de micelas ajustado aos resultados experimentais do espalhamento de raios-X. A formação desses agregados pode ser explicada pelo balanço das interações atrativa de van der Waals, repulsiva coulombiana e de volume excluído, esta última a partir de considerações sobre a solvatação das micelas de anfifílico no meio aquoso. / We studied the following type I lyotropic mesophases, which are oriented spontaneously in the presence of magnetic field, with the symmetry axis parallel to the field: potassium laurate/KCl/H2O and cesium decilsulfate/CsNO3/H2O; was also studied lyotropic mesophase potassium laurate /H2O, which does not exhibit the property of spontaneous magnetic orientation. We used the techniques of X-ray diffraction at high and low angles, and an ancillary, polarized light microscopy, differential scanning calorimetry and cryofracture (\"freeze etching\").

Foram estudadas as seguintes mesofases liotrópicas tipo I, que se orientam espontaneamente em presença de campo magnético, com o eixo de simetria paralelo ao campo: laurato de potássio/KCl/H2O e decilsulfato de césio/CsNO3/H2O; foi estudada também a mesofase liotrópica laurato de potássio/H2O, que não apresenta a propriedade de orientação magnética espontânea. Foram utilizadas as técnicas da difração de raios-X em alto e baixo ângulos e, de forma acessória, microscopia óptica de luz polarizada, calorimetria diferencial de varredura e criofratura( freeze etching). A mesofases foram acondicionadas em diferentes tipos de porta-amostras com e sem tratamento químico de superfície, submetidas a campos magnético e elétrico, bem como a variações de temperatura. Esse estudo possibilitou a identificação de geometria das unidades difratoras, confirmando o modelo de micelas cilíndricas, para o tipo I, bem como forneceu evidências da influência dos efeitos de superfície e da formação de agregados de micelas com dimensões variadas, que originaram os padrões de difração. Foi confirmada a coexistência das fases hexagonal infinita e tipo I em equilíbrio termodinâmico. Foi construído um modelo de agregados de micelas ajustado aos resultados experimentais do espalhamento de raios-X. A formação desses agregados pode ser explicada pelo balanço das interações atrativa de van der Waals, repulsiva coulombiana e de volume excluído, esta última a partir de considerações sobre a solvatação das micelas de anfifílico no meio aquoso. / We studied the following type I lyotropic mesophases, which are oriented spontaneously in the presence of magnetic field, with the symmetry axis parallel to the field: potassium laurate/KCl/H2O and cesium decilsulfate/CsNO3/H2O; was also studied lyotropic mesophase potassium laurate /H2O, which does not exhibit the property of spontaneous magnetic orientation. We used the techniques of X-ray diffraction at high and low angles, and an ancillary, polarized light microscopy, differential scanning calorimetry and cryofracture (\"freeze etching\").

Tao, Yin = 納米線在液晶中的動力學 / 陶寅. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Abstracts in English and Chinese. / Tao, Yin = Na mi xian zai ye jing zhong de dong li xue / Tao Yin. / Abstract --- p.I / 摘要 --- p.III / Acknowledgement --- p.IV / List of Figures --- p.VIII / List of Tables --- p.XV / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1. --- Background --- p.1 / Chapter 1.2. --- Review of Liquid Crystals --- p.2 / Chapter 1.2.1. --- Basic concepts --- p.2 / Chapter 1.2.2. --- Physical Properties of liquid crystals --- p.5 / Chapter 1.3. --- Manipulation of nanowires in suspensions --- p.8 / Chapter 1.3.1. --- Longitudinal Anchoring of liquid crystals --- p.8 / Chapter 1.3.2. --- Dielectrophoretic force and torque --- p.12 / Chapter 1.3.3. --- Measurement of conductivity --- p.15 / Chapter 1.4. --- Our motivation and work --- p.17 / Reference --- p.19 / Chapter Chapter 2 --- Experiments --- p.22 / Chapter 2.1. --- Nematic Liquid Crystal Cell Design and Fabrication --- p.22 / Chapter 2.1.1. --- Parallel Plate Capacitor like Liquid Crystal Cell --- p.22 / Chapter 2.1.2. --- In-Plane Switching Liquid Crystal Cell --- p.23 / Chapter 2.2. --- Filling of liquid crystals and dispersing nanowires --- p.28 / Chapter 2.3. --- Measurements --- p.30 / Chapter 2.3.1. --- Measurement of alignment and reorientation of the nanowires --- p.30 / Chapter 2.3.2. --- Measurements of the optical transmittance of liquid crystal cell --- p.31 / Chapter 2.4. --- Experimental Procedures --- p.33 / Chapter 2.4.1. --- Study of the relaxation of liquid crystals and nanowires --- p.33 / Chapter 2.4.2. --- Study of response of liquid crystals and nanowires to applied E field --- p.34 / Reference --- p.35 / Chapter Chapter 3 --- Numerical simulations of the motion of liquid crystals --- p.36 / Chapter 3.1. --- Leslie-Ericsson equation --- p.36 / Chapter 3.2. --- Response and relaxation of liquid crystals --- p.39 / Chapter 3.2.1. --- Parallel plate capacitor like liquid crystal cells --- p.39 / Chapter 3.2.2. --- In-plane switching liquid crystal cells --- p.45 / Reference --- p.49 / Chapter Chapter 4 --- Method of analysis --- p.50 / Chapter 4.1. --- Deduction of the orientation of nanowires --- p.50 / Chapter 4.1.1. --- Parallel plate capacitor like liquid crystal cell --- p.50 / Chapter 4.1.2. --- In-plane switching liquid crystal cells --- p.52 / Chapter 4.2. --- Methods of curve fitting to experimental data --- p.54 / Chapter 4.2.1. --- Procedures of fitting the curves of transmission --- p.54 / Chapter 4.2.2. --- Procedures of fitting the curves of angle β (t) and φ (t)…… --- p.57 / Reference --- p.64 / Chapter Chapter 5 --- Results and discussion --- p.65 / Chapter 5.1. --- Study of the relaxation of nanowires and liquid crystals --- p.65 / Chapter 5.1.1. --- Dependence on the length of nanowires --- p.65 / Chapter 5.1.2. --- Dependence on the temperature of liquid crystals --- p.82 / Chapter 5.2. --- Study of the responses of nanowires and liquid crystals to E field --- p.89 / Chapter 5.2.1. --- Dependence on the applied E field --- p.89 / Chapter 5.2.2. --- Dependence on the length of nanowires --- p.112 / Chapter 5.2.3. --- Dependence on the temperature of liquid crystal --- p.116 / Reference --- p.122 / Chapter Chapter 6 --- Conclusions --- p.123 / Appendix 1 --- p.125 / Appendix 2 --- p.132

Tam, Yiu Ho = 納米線在液晶中的取向研究 / 譚耀豪. / "November 2009." / Accompanying CD-ROM contains data files. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 79-83). / Abstracts in English and Chinese. / Library's copy: lacks accompanying CD-ROM. / Tam, Yiu Ho = Na mi xian zai ye jing zhong de qu xiang yan jiu / Tan Yaohao. / Abstract --- p.1 / 摘要 --- p.2 / Acknowledgements --- p.3 / Table of contents --- p.4 / Chapter Chapter 1 --- Introduction --- p.8 / Chapter 1.1 --- Background --- p.8 / Chapter 1.2 --- Review of Liquid crystals --- p.8 / Chapter 1.2.1 --- Molecular structure --- p.8 / Chapter 1.2.2 --- Phases --- p.10 / Chapter 1.2.3 --- Classification of liquid crystalline phases --- p.11 / Chapter 1.2.4 --- Elastic property --- p.12 / Chapter 1.2.5 --- Electrical property --- p.13 / Chapter 1.2.6 --- Optical property --- p.14 / Chapter 1.2.7 --- Alignment methods of liquid crystals --- p.14 / Chapter 1.2.8 --- Dynamics of the director of liquid crystals --- p.15 / Chapter 1.2.9 --- Transmittance calculations --- p.17 / Chapter 1.3 --- Interactions between liquid crystal and nanorods --- p.19 / Chapter 1.3.1 --- Longitudinal anchoring --- p.19 / Chapter 1.3.2 --- Theoretical model of the elastic interaction --- p.20 / Chapter 1.4 --- Motivations --- p.22 / Chapter 1.5 --- Our work --- p.23 / Chapter 1.6 --- Overview of the thesis --- p.23 / Chapter Chapter 2 --- Experiments --- p.24 / Chapter 2.1 --- Cell fabrications --- p.24 / Chapter 2.2 --- Filling of liquid crystal and dispersing nanorods --- p.26 / Chapter 2.3 --- Measurements --- p.27 / Chapter 2.3.1 --- Measurements of alignment and deduction of the orientation of nanorods --- p.27 / Chapter 2.3.2 --- Measurements of the optical transmittance of liquid crystal cells --- p.27 / Chapter 2.4 --- Experimental procedures --- p.29 / Chapter 2.4.1 --- Study of the statics of nanorods and liquid crystal --- p.29 / Chapter 2.4.2 --- Study of the dynamics of nanorods and liquid crystal --- p.30 / Chapter Chapter 3 --- Numerical solutions of the equations of motions --- p.31 / Chapter 3.1 --- Solving procedures --- p.31 / Chapter 3.1.1 --- Conversion of differential equations into difference equations --- p.31 / Chapter 3.1.2 --- Solving algorithm --- p.33 / Chapter 3.2 --- Comparison of numerical and analytical solutions --- p.35 / Chapter 3.2.1 --- Analytic solution of a simplified equation of motion --- p.35 / Chapter 3.2.2 --- Checking for the agreement between the numerical and analytic results --- p.36 / Chapter 3.2.3 --- Checking for the accuracy of the numerical results --- p.39 / Chapter Chapter 4 --- Method of analysis --- p.41 / Chapter 4.1 --- Deduction of the orientation of nanorods --- p.41 / Chapter 4.2 --- Method of curves fitting to experimental data --- p.43 / Chapter 4.2.1 --- Procedures of fitting the transmission curves --- p.43 / Chapter 4.2.2 --- Procedures of fitting the curves of angle ß --- p.44 / Chapter Chapter 5 --- Results and discussion --- p.48 / Chapter 5.1 --- Study of the statics of nanorods and liquid crystal --- p.48 / Chapter 5.1.1 --- Study of the alignment ability of liquid crystal on the nanorods --- p.48 / Chapter 5.1.2 --- Study of the longitudinal anchoring effect of liquid crystal on the nanorods --- p.54 / Chapter 5.2 --- Study of the dynamics of nanorods and the liquid crystal --- p.57 / Chapter 5.2.1 --- Dependence on the length of nanorods --- p.57 / Chapter 5.2.1 --- Temperature dependence on the LC-nanorod interaction --- p.66 / Chapter Chapter 6 --- Conclusions --- p.76 / References --- p.79 / Appendices --- p.84

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.

No description available.

Ferroelectric liquid crystals (FLCs) are being investigated as alternatives to nematic liquid crystals in display applications due to their low power requirements and fast switching times. Commercial FLCs consist of a chiral dopant in an achiral smectic C (SmC) liquid crystal host. A bulk property that arises from the chiral nature of this mixture is a spontaneous polarization (PS), which depends on the polarization power of the chiral dopant (δp). The magnitude of δp reflects the ability of a dopant to induce a polarization in an achiral host. It has been proposed that the magnitude of δp can be enhanced by matching dopant and host structures, which may enhance the propagation of chiral perturbations from the dopant to the host. This is known as the chirality transfer feedback (CTF) model. Previous studies in the Lemieux lab featured 2H NMR to detect chiral perturbations exerted by a dopant on the liquid crystal host based on the observation of pairs of quadrupolar doublets in the 2H NMR spectra. In the work described herein, the contribution of chirality transfer feedback to the difference in quadrupolar splitting between pairs of quadrupolar doublets (ΔΔνQ) was assessed by 2H NMR spectroscopy. These experiments confirmed the results reported by Finden and Yuh by demonstrating the presence of chiral perturbations exerted by a diester substituted 6,6’-spirobiindandione dopant ((RS)-2.6-d4) on the achiral SmC host NCB76, and the absence of those perturbations using the diester substituted 5,5’-spirobiindandione analogue ((RS)-2.3-d4). Subsequent studies explored the effect of modifying the chiral topography of the 2,2’-spirobiindan-1,1’-dione core on the magnitude of δp. Both the 5,5’- and 6,6’-disubstituted cores were reduced to give the corresponding mono-carbonyl derivatives ((R)-3.4-d4 and (R)-3.8-d4), substituted with ether side-chains. Finally, ester side-chains were added to the 6,6’- mono-carbonyl derivative ((R)-3.9-d4) for comparison with previous experiments. The ferroelectric induction properties of these dopants were investigated in NCB76 at mole fractions ranging from xd = 0.03 – 0.10. The mono-carbonyl 5,5’- and 6,6’-diether dopants gave absolute polarization powers of 120 nC/cm2 and 123 nC/cm2 respectively, which are not significantly different. This suggests that a reduction in the chiral topography of the spirobiindandione core greatly affects the polarization power of the dopant and may reduce the contribution from chirality transfer to δp. This was confirmed by a measurement of the polarization power of the 6,6’-diester mono-carbonyl dopant (R)-3.9-d4 in NCB76, which gave a δp value of 117 nC/cm2. / Thesis (Master, Chemistry) -- Queen's University, 2008-07-11 15:10:53.56

Ferroelectric liquid crystals (FLCs) have been investigated as the basis for a new type of liquid crystal display because of their fast switching times. Commercial FLC materials are mixtures consisting of a small amount of chiral dopant in an achiral liquid crystal host with an isotropic-nematic-smectic A-smectic C (INAC) phase sequence, which is required to achieve proper alignment between glass slides with rubbed polyimide alignment layers. However, the layer contraction occurring at the SmA-SmC phase transition on cooling from isotropic liquid is a severe problem that leads to a buckling of the smectic layers and results in zigzag defects that drastically degrade the optical quality of FLC films. To solve this problem, we are focusing on a new class of liquid crystal molecules with minimal or no smectic layer shrinkage at the SmA-SmC transition which is referred to as ‘de Vries-like.’ Previous work in the Lemieux group has shown that combining structural elements promoting SmA and SmC phases in a single molecule increases de Vries-like behavior. Giesselmann et. al. suggest that a correlation exists between the temperature range of the SmA phase and de Vries-like behavior. In the study described herein, two homologous series of molecules with 2-phenylpyrimidine cores with siloxane-terminated side-chain (SmC promoting element) and a chloro-terminated side-chain (SmA promoting element)are synthesized and characterized by polarized optical microscopy, differential scanning calorimetry and small-angle X-ray diffraction (SAXS). The reduction factor R for series 1.13 from 0.36 to 0.46 and for series 1.14 from 0.47 to 0.54. Results show that, although there is some correlation between % layer contraction and SmA temperature range, it can be explained primarily by differences in tilt angle θ. When θ is taken into account in the R values, there is no correlation. Another aspect of the study described herein, two siloxane-terminated 2-phenylpyrimidine chiral dopants are synthesized and characterized by polarized optical microscopy, differential scanning calorimetry and small-angle X-ray diffraction (SAXS). / Thesis (Master, Chemistry) -- Queen's University, 2009-11-30 13:42:44.584