title: Floating nematic phase in colloidal platelet-sphere mixtures.
abstract: The phase behaviour of colloidal dispersions is interesting for fundamental reasons and for technological applications such as photonic crystals and electronic paper. Sedimentation, which in everyday life is relevant from blood analysis to the shelf life of paint, is a means to determine phase boundaries by observing distinct layers in samples that are in sedimentation-diffusion equilibrium. However, disentangling the effects due to interparticle interactions, which generate the bulk phase diagram, from those due to gravity is a complex task. Here we show that a line in the space of chemical potentials µ(i), where i labels the species, represents a sedimented sample and that each crossing of this sedimentation path with a binodal generates an interface under gravity. Complex phase stacks can result, such as the sandwich of a floating nematic layer between top and bottom isotropic phases that we observed in a mixture of silica spheres and gibbsite platelets.
authors.affiliation: Theoretische Physik II, Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: de las Heras
authors.forename: Nisha
authors.initials: N
authors.lastname: Doshi
authors.forename: Terence
authors.initials: T
authors.lastname: Cosgrove
authors.forename: Jonathan
authors.initials: J
authors.lastname: Phipps
authors.forename: David I
authors.initials: DI
authors.lastname: Gittins
authors.forename: Jeroen S
authors.initials: JS
authors.lastname: van Duijneveldt
authors.forename: Matthias
authors.initials: M
authors.lastname: Schmidt
mesh_terms: D001792:Blood Platelets / Q000737:chemistry*; D001799:Blood Sedimentation; D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization; D006112:Gravitation; D008962:Models, Theoretical; D055095:Optics and Photonics; D012822:Silicon Dioxide / Q000737:chemistry
chemical_list: D003102:Colloids; D012822:Silicon Dioxide