- Using neutron reflection to understand the structural origin of liquid crystal lubrication. LLE Mears, T Cosgrove, G Magro, SW Prescott, RM Richardson, MWA Skoda, WM de Vos and H Zimmerman. Faraday Discussion 156: Tribology, Southampton, April 2012.
The use of liquid crystals as high quality lubricants has been a subject of scientific research for over two decades but has yet to find any major technological application. Liquid crystals clearly have a positive effect on lubrication but the origin of the phenomena is not well understood. There are a number of possible explanations: a surface-induced smectic layer may coat the solid surfaces, thus smoothing asperities; there may be a strongly adsorbed monomolecular film to enhance boundary layer lubrication; the near surface anchoring of the nematic director may act to oppose film thinning, thus keeping the two surfaces apart. Confinement and the surface structure it causes are therefore key to tribological behaviour. Recently we have developed a novel sample environment to study the structure of thin films under confinement using neutron reflection. The technique of neutron reflection is useful for studying a buried interface, using silicon’s relative transparency to neutrons. We have plans to conduct a series of neutron and X-ray experiments to investigate the structure of different liquid crystal films under confinement, which will begin to unravel the origin of liquid crystal lubrication. Here, we intend to present some very recent results from our first experiment on the confinement of cyanobiphenyls with varying chain lengths. The contrast of core deuterated CBs allows us to observe smectic wetting behaviour and its response to confinement. The rest of the planned experiments will also be covered including a new similar confinement cell which uses X-ray reflection and is currently under development.
Last edited: Friday September 10, 2010
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