Three-Phase Coexistence in Colloidal Rod-Plate Mixtures.

Aqueous suspensions of clay particles, such as montmorillonite (MMT) platelets and sepiolite (Sep) rods, tend to form gels at concentrations around 1 vol %. For Sep rods, adsorbing sodium polyacrylate to the surface allows for an isotropic-nematic phase separation to be seen instead. Here, MMT is added to such Sep suspensions, resulting in a complex phase behavior.

Isotropic-nematic phase transition of polydisperse clay rods.

Rod-like colloidal particles are known to display an isotropic-nematic phase transition on increase of concentration, as predicted already by Onsager. Both natural clay particles and synthetic rods tend to be polydisperse, however, and the question arises how to allow for this in comparing experimental observations with theory. Experimental data for a wide range of samples (both from the literature and the new results) have been collated, with aspect ratios ranging from 14 to 35.

Isotropic-nematic phase transition in aqueous sepiolite suspensions.

Aqueous suspensions of sepiolite clay rods in water tend to form gels on increase of concentration. Here it is shown how addition of a small amount (0.1% of the clay mass) of a common stabiliser for clay suspensions, sodium polyacrylate, can allow the observation of an isotropic-nematic liquid crystal phase transition.