The Synthesis and Evaluation of Novel Bent-core Liquid Crystals Designed to Generate a Biaxial Nematic Phase

Lead Research Organisation: University of Hull
Department Name: Physical Sciences

Abstract

It is commonly recognised that matter can exist in three states, solid, liquid and gas, however, some materials, notably those that consist of rod-shaped molecules, can additionally show one or more 'liquid crystal' phase(s). Liquid crystal phases are distinct phases of matter that have molecular orderings intermediate between those of the common liquid state and those of the common crystalline solid state. The smectic phases (several are known) are liquids that are quite viscous because the degree of molecular ordering is close that of solids. The nematic phase is very fluid because the only molecular ordering is a statistically parallel arrangement of molecules. It is this fluid nematic liquid crystal that is used in the widely available flat-panel liquid crystal displays that are now used for watches, calculators, mobile telephones, cameras, lap-top computers, desk-top monitors and more recently large area flat-panel televisions. In these devices, the rod-like liquid crystal molecules have their orientation switched by the application of a small electric field (a few volts), and although switching times are quite fast, around 50 microseconds, faster switching would be advantageous, and open up a whole new area of fast switching applications in displays, telecommunications and optical devices.In the nematic phase, the rod-like molecules have a statistically parallel arrangement of the molecules and in this arrangement there is only one axis (the optic axis) through which polarised light travels through with equal velocity, hence the phase is termed uniaxial. Bent-core (but not too bent) molecules can also exhibit the nematic liquid crystal phase, however, the bent-core molecular structure can give rise to a biaxial nematic phase, in which, as the name implies, there are two optic axes. A biaxial nematic phase is of fundamental scientific interest, and additionally it is of technological interest because switching in such a biaxial nematic phase would be much faster enabling the advantageous devices mentioned above, and possibly facilitate the development of novel high technology applications.So far, very few compounds have been proven to generate a biaxial nematic phase, and these are only exhibited at temperatures of around 200 C, and over a relatively short temperature range; which obviously makes evaluation difficult, and use in applications impossible. This proposed research is designed to thoroughly investigate the structure-property relationships of bent-core molecular structures in the generation of the biaxial nematic phase, through the synthesis and evaluation of novel material designs, with a view to providing the phase over a wider temperature range, at or close to room temperature; thus facilitating the evaluation of physical properties and enabling use in applications discussed above.

Publications

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Fergusson, K.M. Targeting the nematic phase generated by bent-core molecular architectures in 23rd British Liquid Crystal Society Annual Conference, Bristol, April 2009

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Fergusson, K.M. Fluorinated bent-core compounds targeting the biaxial nematic phase: synthesis and mesomorphic properties in 21st British Liquid Crystal Society Annual Conference, Sheffield, March, 2007

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Fergusson, K.M. Targeting the nematic phase generated by bent-core molecular architectures in 12th International Conference on Ferroelectric Liquid Crystals, Zaragoza, Spain, August 2009

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Fergusson, K.M. Bent-core and hockey-stick shaped molecular structures exhibiting interesting morphologies in 12th International Conference on Ferroelectric Liquid Crystals, Zaragoza, Spain, August 2009

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Fergusson, K.M. Novel fluorinated bent-core esters: interesting synthetic strategies and mesomorphic properties in 22nd International Liquid Crystal Conference, Jeju, Korea, June, 2008

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Fergusson, K.M. Novel fluorinated bent-core esters: interesting synthetic strategies and mesomorphic properties in 22nd British Liquid Crystal Society Annual Conference, Norwich, March 2008

 
Description A novel range of bent-core materials were synthesized and evaluated for their melting points, transition temperatures and mesophase morphologies. The novel materials have been used in the formulation of mixtures, evaluated for a range of physical properties in order to evaluate their suitability for applications, notable liquid crystal displays.
Exploitation Route Further research and development in the area.
Sectors Chemicals,Digital/Communication/Information Technologies (including Software),Electronics,Manufacturing, including Industrial Biotechology

 
Description Findings have been used in terms of physical property evaluation of materials generated, and in the further research activities in the area
First Year Of Impact 2006
Sector Chemicals,Digital/Communication/Information Technologies (including Software),Electronics,Manufacturing, including Industrial Biotechology
Impact Types Cultural,Societal

 
Description Kingston Chemicals Ltd 
Organisation University of Hull
Department Kingston Chemicals
Country United Kingdom 
Sector Private 
PI Contribution The compounds generated through research grant EP/D505399/1 were sent to this collaborator for mixture formulation and evaluation of mesomorphic properties.
Collaborator Contribution This collaborator evaluated compounds generated through research grant EP/D505399/1 in mixture formulation for evaluation of mesomorphic properties.
Impact None.
Start Year 2006
 
Description Otto-von-Guericke University Magdeburg 
Organisation The Otto-von-Guericke University Magdeburg
Country Germany 
Sector Academic/University 
PI Contribution Compounds generated through research grant EP/D505399/1 were sent to this collaborator for evaluation of physical properties.
Collaborator Contribution Physical properties were evaluated by this collaborator from compounds generated through research grant EP/D505399/1.
Impact None.
Start Year 2006
 
Description Universidade de Lisboa 
Organisation University of Lisbon
Country Portugal 
Sector Academic/University 
PI Contribution The research grant EP/D505399/1 generated compounds which were sent to this collaborator for evaluation by NMR techniques.
Collaborator Contribution This collaborator evaluated materials synthesized through research grant EP/D505399/1 by NMR techniques.
Impact None.
Start Year 2006
 
Description University of California, Merced 
Organisation University of California, Merced
Country United States 
Sector Academic/University 
PI Contribution Compounds generated through research grant EP/D505399/1 were sent to this collaborator for evaluation of physical properties.
Collaborator Contribution Physical properties were evaluated by this collaborator from compounds generated through research grant EP/D505399/1.
Impact Low electric-field-induced switching in the B1 bent-core liquid crystal phase, J. Kirchoff, L.S. Hirst, K.M. Fergusson, M. Hird, App. Phys. Lett., 2007, 90, 161905.
Start Year 2006
 
Description University of Sheffield 
Organisation University of Sheffield
Country United Kingdom 
Sector Academic/University 
PI Contribution The research grant EP/D505399/1 generated compounds which were sent to this collaborator for evaluation by X-ray techniques.
Collaborator Contribution This collaborator evaluated materials synthesized through research grant EP/D505399/1 by X-ray techniques.
Impact None.
Start Year 2006