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The Use of Twisted Nematic Displays in the Evaluation of Chirality and its Effects at the Molecular Level

Jia, Xiang (2014) The Use of Twisted Nematic Displays in the Evaluation of Chirality and its Effects at the Molecular Level. PhD thesis, University of York.

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Abstract

The work in this thesis can be divided into three areas: chirality and structure of dopants, host dependency and investigation of reaction pathways in the search for chiral induction. The ‘reverse-twist disclination’ method first reported by Raynes was used to determine the helical twisting power (HTP) of a selection of chiral materials dissolved in achiral nematic liquid crystal hosts: E7, PCH7, BL036 and ZLI559. The chiral materials studied include oxazoline and lactate derived chiral dopants, commercial liquid crystal chiral dopants and thalidomide. One of the most notable outcomes is that the overall shape of the molecular structure of a chiral dopant dictates the magnitude of HTP values, whereby a propellar-like molecular shape consistently provides high HTP values. Additionally, the technique used was found to be very sensitive to differences in the optical purity of the dopant. Host dependency was found for all chiral dopants suggesting that HTP should not be considered as an intrinsic property of a chiral material but rather a property that results from a combination of host and dopant. It had been reported in the literature that the Mitsunobu reaction can, for racemic secondary alcohols, give non-racemic products, a remarkable result that implies that mirror symmetry can be broken on a macroscopic scale. The effect of various different reaction conditions upon the optical purity of 1-methylheptyl esters was studied. The resulting materials were analysed via the reverse-twist disclination method and occasionally the Mitsunobu reaction was found to produce a product that was indeed optically active. Without exception, the Steglich reaction was only found to preserve mirror symmetry and produce non-chiral products.

Item Type: Thesis (PhD)
Keywords: Liquid Crystal Chirality
Academic Units: The University of York > Chemistry (York)
Identification Number/EthosID: uk.bl.ethos.635416
Depositing User: Mr Xiang Jia
Date Deposited: 17 Feb 2015 15:12
Last Modified: 24 Jul 2018 15:20
URI: http://etheses.whiterose.ac.uk/id/eprint/7952

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