Liquid-crystalline phases were discovered more than a century ago.1 Up to now, tens of thousands of organic liquid crystals were discovered. In contrast, only a few mineral liquid crystals were characterized. In comparison to organic liquid crystals, inorganic ones may possess enhanced electrical, optical, magnetic properties and thermal stability. 1 The currently known lyotropic mineral liquid crystals, which formed in dispersions of anisometric inorganic particles at some critical concentration, were summarized in two review articles. 2,3 The liquid-crystalline phase of V2O5 suspensions shows an electro-optic effect and is used for measurement of residual dipolar couplings of unlabeled biomolecules. 4,5 Mineral liquid-crystal moieties can differ largely in size from one system to another, but they are in a colloidal range.

The intercalation reaction of polyoxyethylene sulfate (PEGS) withMg-Al-nitrate [Mg-Al-NO3] layered double hydroxide (LDH)wasinvestigated by using X-ray diffraction, infrared spectroscopy, and transmission electron microscopy (TEM). X-ray diffractograms showed that the basal spacing of the [Mg-Al-NO3]LDH with PEGS as the intergallery anion expanded from 0.89 to 2.37nm to form [Mg-Al-(PEGS)], but no expansion of the basal spacing was observed when poly(ethylene glycol) (PEG) reacted with [Mg-Al-NO3]. The characteristic absorption bands of the organic anion in the infrared spectra were obtained after prolonged treatment with deionized water, demonstrating the stability of the intercalation compounds. Furthermore, TEM analysis revealed that [Mg-Al-NO3], which consisted of hexagonal particles approximately 100-120nm in length, changed into monodisperse rigid spheres approximately 200 nm in diameter after the intercalation of PEGS.

The rheological properties of hydrotalcite-like compounds (HTlc)/sodium montmorillonite (MT) suspensions, which have formed gel-like structures, have been investigated. Special emphasis has been placed on the phenomenon of thixotropy. Usually, the structure recovery at rest after steady shear is considered the fundamental thixotropic process. And the recovery process was performed at the amplitude oscillatory shear measurements and the steady shear measurements. The oscillatory experiments were performed in the linear viscoelastic region so as tomakethe recovery process undisturbed. In the oscillatory experiments, η* increases monotonically with the time after the preshear process, and even after 3 h no equilibrium viscosity value of the suspension is reached. A single power law |η*|～tn holds within the time regime from 10 s to 3h, and the exponent n ) 0.158±0.10 is not only independent of the concentration and composition of the clay and the HTlc but also independent of mechanical pretreatment of the suspension. In the oscillatory experiments, two kinds of Na-MT were used, and almost the same value of exponent n was obtained. This type of kinetics has not been reported so far for the thixotropic recovery in the mixed suspension. And the reorganization of the gel structure is interpreted as a cooperative self-delaying process similar to the aging of glassy polymers or precipitation from supersaturated solid solutions. In the steady experiments, the recovery process was monitored at the low shear rate, and è does not always increase with the time. In the recovery process, the formation of the network was disturbed by the shear rate to some extent. When the structure strength (which is indicated by the value of the viscosity) of the system is low, the disturbance of the shear rate on the recovery process is weak, which becomes distinct when the structure strength is high.