Investigating the chirality transfer feedback model in ferroelectric liquid crystals using deuterium NMR spectroscopy

dc.contributor.authorHuntley, Christa Margareten
dc.contributor.supervisorLemieux, Robert P.en
dc.date2008-07-11 15:10:53.56's University at Kingstonen
dc.descriptionThesis (Master, Chemistry) -- Queen's University, 2008-07-11 15:10:53.56en
dc.description.abstractFerroelectric 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.en
dc.format.extent4945849 bytes
dc.relation.ispartofseriesCanadian thesesen
dc.rightsThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.en
dc.subjectLiquid crystalsen
dc.subjectMaterials chemistryen
dc.titleInvestigating the chirality transfer feedback model in ferroelectric liquid crystals using deuterium NMR spectroscopyen
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
4.72 MB
Adobe Portable Document Format