Dynamics of the floating nematic phase formation in platelet suspension with thickness polydispersity by sedimentation†
An inverted phase coexistence, where an ordered phase appears on top of a disordered phase, has been observed in polydisperse colloidal suspensions. Herein, we studied the dynamics of this phenomenon in a suspension of a mixture of two types of platelets, namely, thick and thin. We show that the thick platelets preferentially sediment first excluding the thin platelets, and create a region enriched with thin platelets at some place above the bottom, which eventually gives the inverted configuration. We show that such interplay between the sedimentation and the isotropic–nematic phase transition can cause a rich and complex sedimentation dynamic. Depending on the initial concentration and the gravity strength, the interface between the isotropic phase and the nematic phase can move up or down during the sedimentation, and a variety of final equilibrium structures can appear.