Sterically stabilized nano-platelets were prepared by treating montmorillonite clay with both a surfactant and a polymeric stabilizer. These nano-platelets, for the first time, formed stable suspensions in a thermotropic liquid crystal(LC), 5CB. In the isotropic state of the LC, static light scattering confirmed that the clay nano-platelets were freely suspended, with no aggregation detected even after repeated temperature cycling. Small-angle X-ray scattering revealed that the clay was nearly completely delaminated in the LC, with some stacks of a few clay nano-platelets having formed. Differential scanning calorimetry of the LC/clay suspensions showed a small but non-monotonic shift of the I-N transition temperature. This behavior is similar to that of LC confined in porous media, with an initial increase of the transition temperature on adding clay being ascribed to the effect of surface anchoring facilitating the formation of the nematic phase; whereas a decrease at higher clay concentrations (or equivalently, for smaller pores) is ascribed to confinement effects frustrating the formation of the nematic phase. This interpretation is supported by polarizing light microscopy which showed the nematic domain size becoming smaller on increasing the clay concentration.

41044 modified by 158.130.30.30 on 2-15-2007-->