Depletion-induced biaxial nematic states of boardlike particles

• Published in: Journal of physics. Condensed matter Vol. 24; no. 28; p. 284128
• Main Authors: Belli, S, Dijkstra, M, van Roij, R
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Bristol IOP Publishing 18.07.2012; Institute of Physics
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Liquid crystals; Physics; Structure of solids and liquids; crystallography; Mean field approximation; Phase diagrams; Multicritical point; Attraction interaction; Uniaxial crystals; Pair potentials; Second virial coefficient; Density functional method; Ordering; Nematic crystals; Concentration distribution; Particle orientation
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/24/28/284128

With the aim of investigating the stability conditions of biaxial nematic liquid crystals, we study the effect of adding a non-adsorbing ideal depletant on the phase behavior of colloidal hard boardlike particles. We take into account the presence of the depletant by introducing an effective depletion attraction between a pair of boardlike particles. At fixed depletant fugacity, the stable liquid-crystal phase is determined through a mean-field theory with restricted orientations. Interestingly, we predict that for slightly elongated boardlike particles a critical depletant density exists, where the system undergoes a direct transition from an isotropic liquid to a biaxial nematic phase. As a consequence, by tuning the depletant density, an easy experimental control parameter, one can stabilize states of high biaxial nematic order even when these states are unstable for pure systems of boardlike particles.