Europhys. Lett.
Volume 66, Number 1, April 2004
Page(s) 125 - 131
Section Interdisciplinary physics and related areas of science and technology
Published online 01 March 2004
Europhys. Lett., 66 (1) , pp. 125-131 (2004)
DOI: 10.1209/epl/i2003-10140-1

Sedimentation and multi-phase equilibria in mixtures of platelets and ideal polymer

H. H. Wensink and H. N. W. Lekkerkerker

Van 't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute Utrecht University - Padualaan 8, 3584 CH Utrecht, The Netherlands

(Received 19 November 2003; accepted in final form 26 January 2004)

The role of gravity in the phase behaviour of mixtures of hard colloidal plates without and with non-adsorbing ideal polymer is explored theoretically. By analyzing the (macroscopic) osmotic equilibrium conditions, we show that sedimentation of the colloidal platelets is significant on a height range of even a centimeter. Gravity enables the system to explore a large density range within the height of a test tube which may give rise to the simultaneous presence of multiple phases. As to plate-polymer mixtures, it is shown that sedimentation may lead to a four-phase equilibrium involving an isotropic gas and liquid phase, nematic and columnar phase. The phenomenon has been observed experimentally in systems of colloidal gibbsite platelets mixed with PDMS polymer.

82.70.Dd - Colloids.
64.70.Md - Transitions in liquid crystals.

© EDP Sciences 2004