Eur. Phys. J. E 4, 21-28
Cellular solid behaviour of liquid crystal colloids 2. Mechanical properties
V.J. Anderson and E.M. Terentjev.Cavendish Laboratory, The University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK emt1000@cus.cam.ac.uk
(Received 13 March 2000 and Received in final form 6 June 2000)
Abstract
This paper presents the results of a rheological study
of thermotropic nematic colloids aggregated into cellular
structures. Small sterically stabilised PMMA particles dispersed
in a liquid crystal matrix densely pack on cell interfaces, but
reversibly mix with the matrix when the system is heated above
. We obtain a remarkably high elastic modulus,
, which is a nearly linear function of
particle concentration. A characteristic yield stress is required
to disrupt the continuity of cellular structure and liquify the
response. The colloid aggregation in a "poor nematic"MBBA has
the same cellular morphology as in the "good nematic"5CB, but
the elastic strength is at least an order of magnitude lower.
These findings are supported by theoretical arguments based on the
high surface tension interfaces of a foam-like cellular system,
taking into account the local melting of nematic liquid and the
depletion locking of packed particles on interfaces.
61.30.-v - Liquid crystals..
82.70.-y - Disperse systems..
81.40.Jj - Elasticity and anelasticity, stress-strain relations..
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001
