title: Binary separation in very thin nematic films: thickness and phase coexistence.
abstract: The behavior as a function of temperature of very thin films (10 to 200 nm) of pentylcyanobiphenyl on silicon substrates is reported. In the vicinity of the nematic-isotropic transition we observe a coexistence of two regions of different thicknesses: thick regions are in the nematic state while thin ones are in the isotropic state. Moreover, the transition temperature is shifted downward following a 1/h(2) law ( h is the film thickness). Microscope observations and small-angle x-ray scattering allowed us to draw a phase diagram which is explained in terms of a binary first-order phase transition where thickness plays the role of an order parameter.
authors.affiliation: Physique de la Matière Condensée, Collège de France, URA 792 du CNRS, 11 place Marcelin Berthelot, 75005 Paris, France.
authors.forename: D
authors.initials: D
authors.lastname: van Effenterre
authors.forename: R
authors.initials: R
authors.lastname: Ober
authors.forename: M P
authors.initials: MP
authors.lastname: Valignat
authors.forename: A M
authors.initials: AM
authors.lastname: Cazabat