Europhys. Lett.
Volume 61, Number 5, March 2003
Page(s) 702 - 707
Section Interdisciplinary physics and related areas of science and technology
Published online 01 February 2003
DOI: 10.1209/epl/i2003-00132-1
Europhys. Lett., 61 (5) , pp. 702-707 (2003)

Nematic ordering vs. gelation in suspensions of charged platelets

D. van der Beek and H. N. W. Lekkerkerker

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

(Received 30 September 2002; accepted in final form 16 December 2002)

We study aqueous suspensions of charged gibbsite platelets that show the isotropic (I) to nematic (N) phase transition. This is the first case where the I-N transition in a dispersion of charged colloidal platelets is not impeded by gelation since Langmuir's classic work on dispersions of clay particles more than sixty years ago (J. Chem. Phys., 6 (1938) 873). On increasing particle concentration, our dispersions subsequently show an isotropic, nematic and gel phase. We attribute the shift of the gelation boundary from below to above the I-N transition to the surface modification of the gibbsite platelets with aluminium polycations, which are known to enhance the stability of gibbsite colloids significantly.

82.70.Dd - Colloids.
64.70.Md - Transitions in liquid crystals.
61.30.Eb - Experimental determinations of smectic, nematic, cholesteric, and other structures.

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