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SUMMARY:Solid liquid crystals - Warner\, M (University of Cambridge)
DTSTART:20130108T140000Z
DTEND:20130108T150000Z
UID:TALK42317@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Liquid crystals can become solids when they form glasses or wh
 en liquid crystalline polymers are crosslinked to form rubber. They can sh
 ow properties richer than solids and liquid crystals separately. Glasses h
 ave high moduli and their directors are not mobile with respect to the sol
 id matrix. Rubber maintains the molecular mobility of a liquid\; it can be
  deformed hugely\, has a low modulus\, and its director is mobile. Both ca
 n have their order reduced by heat\, light and solvent\, and then mechanic
 ally contract along the director by a few percent (glasses) and by 100s% (
 rubber). Topological defects in their director fields means that such mech
 anical response generates Gaussian curvature or topology changes.\n\nMobil
 e directors respond to imposed strains by reapportioning natural length in
  directions required by distortions\, rendering their energetic cost zero 
 or very small. If necessary textures of such low cost deformations are req
 uired to comply with boundary conditions in much the same way as in Marten
 site. Indeed such techniques of quasi-convexification have been extended b
 y DeSimone et al to complete and generalise the soft mechanics discovered 
 theoretically and experimentally by physicists and chemists.\n\nI shall sk
 etch some of these phenomena and present recent results on the mechanical 
 and topological effect of disclinations in nematic solids\, and on how pol
 ydomain nematic solids can be super-soft.\n
LOCATION:Seminar Room 1\, Newton Institute
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