Liquid crystal phase transitions in suspensions of polydisperse plate-like particles

Abstract

Colloidal suspensions that form periodic self-assembling structures on sub-micrometre scales are of potential technological interest; for example, three-dimensional arrangements of spheres in colloidal crystals might serve as photonic materials, intended to manipulate light. Colloidal particles with non-spherical shapes (such as rods and plates) are of particular interest because of their ability to form liquid crystals. Nematic liquid crystals possess orientational order; smectic and columnar liquid crystals additionally exhibit positional order (in one or two dimensions respectively). However, such positional ordering may be inhibited in polydisperse colloidal suspensions. Here we describe a suspension of plate-like colloids that shows isotropic, nematic and columnar phases on increasing the particle concentration. We find that the columnar two-dimensional crystal persists for a polydispersity of up to 25%, with a cross-over to smectic-like ordering at very high particle concentrations. Our results imply that liquid crystalline order in synthetic mesoscopic materials may be easier to achieve than previously thought.

Liquid crystal phase transitions in suspensions of mineral colloids: new life from old roots

“…Starting from the materials used in the Buining method [42] to produce boehmite rods, Wierenga et al [56] discovered a synthesis route which yields well-formed hexagonal plate-like gibbsite crystals (diameter 100-200 nm and thickness 5-15 nm). Subsequently, van der Kooij & Lekkerkerker [57] succeeded in sterically stabilizing these gibbsite platelets by grafting a layer of low-molecular-weight PIB molecules onto their surface following the method of Buining & Lekkerkerker [36]. This novel model system of hard colloidal platelets was observed to phase-separate into an isotropic and a nematic LC phase [57].…”

“…Subsequently, van der Kooij & Lekkerkerker [57] succeeded in sterically stabilizing these gibbsite platelets by grafting a layer of low-molecular-weight PIB molecules onto their surface following the method of Buining & Lekkerkerker [36]. This novel model system of hard colloidal platelets was observed to phase-separate into an isotropic and a nematic LC phase [57]. Upon further increasing the particle concentration, van der Kooij et al [58] observed that suspensions of these sterically stabilized plate-like gibbsite colloids also display a columnar phase (figure 4) in good agreement with the computer simulation results of Veerman & Frenkel [51].…”

Liquid Crystalline Nature of K4Nb6O17 Nanosheet Sols and Their Macroscopic Alignment

“…The observed marble pattern, with various interference colors due to the birefringence of the sample, is characteristic of liquid crystalline phases. [21,22] Although we have not identified the type of liquid crystal, lamellar, [28] and columnar, [31] as well as nematic phases, can occur for the present nanosheet colloid.The liquid crystalline state of the niobate nanosheets is highly stable. We observed birefringence even at the concentration of 5 10 ±5 mol dm ±3 or ca.…”

Structure of the repulsive gel/glass in suspensions of charged colloidal platelets

“…These observations provided, in part, the experimental stimulus for the theory put forward by Onsager [1]. However, it took more than half a century before further experimental evidence for liquid crystal phase equilibria in suspensions of plate-like particles was obtained [5][6][7][8][9][10][11][12].…”