Three-Phase Coexistence in Colloidal Rod–Plate Mixtures

Abstract

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. Across a range of clay concentrations, separation into three phases is observed: a lower, nematic phase dominated by Sep rods, a MMT-rich middle layer, which is weakly birefringent and probably a gel, and a dilute top phase. Analysis of phase volumes suggests that the middle layer may contain as much as 6 vol % MMT.

Swelling Inhibition of Liquid Crystalline Colloidal Montmorillonite and Beidellite Clays by DNA

“…Although no biaxial nematic phase appeared in this system, the phase diagram shows up to four distinct liquid-crystalline phases, including several different rod-rich and disk-rich nematic phases. Other examples are mixtures of sepiolite nanorods a few microns long with montmorillonite nanosheets about one micron in diameter 26 . This system has an unusual phase diagram with regions where an isotropic phase coexists with two nematic phases differing by their compositions.…”

The Effects of Size and Shape Dispersity on the Phase Behavior of Nanomesogen Lyotropic Liquid Crystals

“…Woolston and Duijneveldt found that combining montmorillonite (MMT) nanoplatelets with sepiolite (Sep) nanocylinders also showed complex phase behavior [128]. The aqueous MMT alone formed a gel, and aqueous Sep formed a nematic, but the addition of Sep to MMT could result in three-phase coexistence where the bottom layer consisted of a nematic Sep cylinder-rich phase, the middle layer consisted of an MMT platelet-rich phase, and the top layer was a dilute isotropic layer [128]. For all MMT concentrations above 1 vol%, however, the system gelled and the MMT concentration required for gelation decreased as the Sep concentration was increased to 4 vol%.…”

Liquid Crystalline Colloidal Mixture of Nanosheets and Rods with Dynamically Variable Length

“…Prominent examples are the ordered structures found in colloidal systems 4 such as colloid crystals and colloidal LCs. 5 Further, combination of components with dissimilar morphologies such as rod/plate, 6 rod/sphere, 7 plate/sphere, 8 nanosheet/rod, 9 nanosheet/nanosheet, 10 and plate/polymer 11 types of particles also facilitates formation of variety of well-ordered structures. Thus, complexity of the system is a key to develop highly organized and hierarchical structures.…”