Item – Theses Canada

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OCLC number
809970440
Link(s) to full text
LAC copy
LAC copy
Author
Song, Qingxiang.
Title
Investigating the effect of smectic : a temperature range variation on de Vries properties.
Degree
M. Sc. -- Queen's University, 2010
Publisher
Ottawa : Library and Archives Canada = Bibliothèque et Archives Canada, [2011]
Description
2 microfiches
Notes
Includes bibliographical references.
Abstract
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 [theta]. When [theta] 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).
ISBN
9780494650592
0494650591