Large scale structures in liquid crystal/clay colloids

liquid crystal, colloid, SAXS Suspensions of three different clays in K15, a thermotropic liquid crystal have been studied by optical microscopy and small angle X-ray scattering. The three clays were Claytone AF, a surface treated natural montmorillonite, Laponite RD, a synthetic hectorite and mined Sepiolite. The Claytone and Laponite were sterically stabilized whereas Sepiolite formed a relatively stable suspension in K15 without any surface treatment. Micrographs of the different suspensions revealed that all three suspensions contained large scale structures. The nature of these aggregates was investigated using small angle X-ray scattering. For the clays with sheetlike particles, Claytone and Laponite, the flocs contain a mixture of stacked and single platelets. The basal spacing in the stacks was independent of particle concentration in the suspension and the phase of the solvent. The number of platelets in the stack and their percentage in the suspension varied with concentration and the aspect ratio of the platelets. The lath shaped Sepiolite did not show any tendency to organize into ordered structures. Here the aggregates are networks of randomly oriented single rods.