Abstract

A fascinating way to improve the present-day liquid crystal technology consists of imagining to use new liquid crystal phases with “exotic” properties, like the biaxial nematic phase. However, as an essential step in this direction one has to establish the conditions under which such a phase is thermodynamically stable. Inspired by a recent experiment on a colloidal suspension of mineral goethite particles [1], we use a mean field theory to investigate the phase behavior of boardlike particles. By modelling these nanoscopic bricks as cuboids with a hard-body interaction, we analyze the conditions of stability of the long-searched biaxial-nematic phase. We show that under specific conditions size-polydispersity, a common property in most colloids, can increase appreciably the stability of this liquid crystal phase [2]. Moreover, we deduce that this effect can be interpreted in terms of an effective attraction, and therefore that a similar stability could be induced by a non-adsorbing depletant, like a polymeric solution [3].

[1] E. van den Pol et al., Phys. Rev. Lett. 103, 055901 (2009) [2] S. Belli, A. Patti, M. Dijkstra and R. van Roij, Phys. Rev. Lett. 107, 148303 (2011) [3] S. Belli, M. Dijkstra and R. van Roij, J. Phys.: Condens. Matter 24, 284128 (2012)