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Title: Magnetic resonance studies of dimer liquid crystals
Author: Le Masurier, Peter John
ISNI:       0000 0001 3606 3968
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 1996
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A class of liquid crystal materials that has recently generated considerable interest is that of the liquid crystal dimers. Whereas the more familiar monomer systems generally comprise of a single rigid unit connected to a flexible chain, the dimers have two mesogenic groups connected with a flexible spacer. This simple extension allows the creation of a whole group of liquid crystal materials that possess properties fundamentally different to their monomer constituents, properties that resemble to a greater extent those of semi-flexible main chain liquid crystal polymers. The majority of dimer systems synthesised and studied so far can be classed as symmetric dimers; i.e. the two mesogenic groups are identical. However, a second group exists where the dimers have different mesogenic groups, the so-called non-symmetric dimers. These have been observed to display novel smectic phase structures where the layers have varying degrees of interconnection. At one extreme is the interdigitated arrangement for which a layer spacing of �1.8 molecular lengths is observed and at the other is the unusual intercalated where the layer spacing is 0.5 times the molecular length. These layer spacings are thought to result from a favourable unlike quadrupolar interaction between two mesogenic groups in the same layers. In this Thesis we present results from magnetic resonance studies of the non-symmetric α-(4-cyanobiphenyl-4'-yloxy)-ω-(4-n-alkylanilinebenzylidine-4'-oxy) alkanes,, and the symmetric α,ω-bis(4-n-alkylanilinebenzylidene-4'-oxy) alkanes, n.OmO.ns. Measurements have been made of the orientational order of the pure dimers and the dimers in monomer solvents, using ESR and deuterium NMR. These results have then been compared with calculations using the Marcelja-Luckhurst theory. The unusual structure of the intercalated smectic C phase has been probed using orientational dependent ESR studies and a structure proposed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: ESR; NMR; Intercalated smectics