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Gelation versus Liquid Crystal Phase Transitions in Suspensions of Plate-Like Particles
M. C. D. Mourad, J. E. G. J. Wijnhoven, D. D. van 't Zand, D. van der Beek and H. N. W. Lekkerkerker
Philosophical Transactions: Mathematical, Physical and Engineering Sciences
Vol. 364, No. 1847, New Directions in Liquid Crystals (Oct. 15, 2006), pp. 2807-2816
Published by: Royal Society
Stable URL: http://www.jstor.org/stable/25190361
Page Count: 10
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Gelation is a common effect in aqueous suspensions of charged colloidal clay platelets at concentrations as low as 1 wt%. However, in systems of charged gibbsite [Al(OH)₃] platelets, gelation can be delayed to concentrations as high as 50 wt% depending on the ionic strength. We investigated the phase behaviour of this system approaching the state of gelation in the delicate region between attractive and repulsive states that originate from competition between Coulomb repulsion and van der Waals attraction. As a function of the ionic strength, isotropic-nematic, nematic-columnar and isotropic-columnar phase separations were observed. Moreover, compression by gravitational forces allowed us to observe phase separation that is arrested by gelation in the homogeneous suspensions.
Philosophical Transactions: Mathematical, Physical and Engineering Sciences © 2006 Royal Society