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SUMMARY:Liquid crystal foam - Teixeira\, P (ISEL and Universidade de Lisbo
 a)
DTSTART:20130417T100000Z
DTEND:20130417T110000Z
UID:TALK44592@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:We investigate whether a liquid crystal foam\, made by shearin
 g an ionic mesogen\, exhibits the same properties as an ordinary liquid fo
 am. In particular\, for a quiescent foam we find: (i) where three walls me
 et\, they do so at approximately 120-degree angles\, for all times studied
 \; (ii) Lewiss law of linear relation between cell area and number of side
 s is approximately satisfied at late times\; (iii) the morphological patte
 rns coarsen in time\, both T1 and T2 processes are observed and\, at late 
 times\, evolution is consistent with von Neumanns law\; and (iv) relativel
 y large numbers of 5-sided cells survive up to fairly late times. Results 
 (i) and (iii) suggest that surface tension may play a key role in determin
 ing the physics of this system\, as it does in low-viscosity liquid foams.
  If our mesogen is subjected to controlled shear\, there is a threshold sh
 ear rate below which no foam can form. Above this threshold\, a steady-sta
 te foam pattern is obtained where the mean cell area generally decreases w
 ith increasing shear rate. Furthermore\, the steady-state internal cell an
 gles and distribution of cell number of sides deviate from their equilibri
 um (i.e. zero-shear) values.\n
LOCATION:Seminar Room 1\, Newton Institute
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