Liquid–crystal phase transitions in suspensions of plate–like particles

Abstract

We study the liquid–crystalline phase behaviour of suspensions of hard colloidal platelets, in particular, the relationship between their size polydispersity and the stability of a nematic, columnar and smectic phase. A first–order nematic–to–columnar transition is observed for suspensions up to 25% polydispersity in platelet diameter (σD). However, at densities slightly above nematic–columnar coexistence, the columnar order appears to vanish in the case of σD = 25%, while columnar stability persists for σD = 17%. The observed tolerance of polydispersity in the columnar phase, being a two–dimensional crystal, seems remarkable in light of current predictions for the terminal polydispersity for hard–sphere crystallization and hard–rod smectic ordering.