Mourad M C D, Wijnhoven J E G J, Van't Zand D D, van der Beek D, Lekkerkerker H N W
Van't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Philos Trans A Math Phys Eng Sci. 2006 Oct 15;364(1847):2807-16. doi: 10.1098/rsta.2006.1856.
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.
凝胶化是带电胶态粘土薄片水悬浮液中常见的现象，即使在低至1 wt%的浓度下也会发生。然而，在带电三水铝石[Al(OH)₃]薄片体系中，根据离子强度的不同，凝胶化可能会延迟到高达50 wt%的浓度。我们研究了该体系在接近凝胶化状态时的相行为，该状态处于由库仑排斥力和范德华吸引力之间的竞争所产生的吸引态和排斥态之间的微妙区域。作为离子强度的函数，观察到了各向同性-向列相、向列-柱状相和各向同性-柱状相分离。此外，重力压缩使我们能够观察到在均匀悬浮液中因凝胶化而停止的相分离。
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