DOI: 10.1051/jp2:1993171
J. Phys. II France 3 (1993) 851-864

Columnar phase of pyramidic amphiphiles spread at the air-water interface

A. El Abed¹, P. Muller², P. Peretti¹, F. Gallet² and J. Billard<sup>3

1</sup>  Laboratoire de Physique et Biophysique, Université René Descartes-Paris V, 45 rue des Saints Pères, 75270 Paris Cedex 06, France
²  Laboratoire de Physique Statistique, Ecole Normale Supérieure, 24 rue Lhomond, 75230 Paris Cedex 05, France
³  Laboratoire de Physique de la Matière Condensée, Collège de France, Place Marcelin Berthelot, 75232 Paris Cedex 05, France

(Received 8 July 1992, revised 28 December 1992, accepted 3 March 1993)

Abstract
Two compounds, forming thermotropic liquid-crystalline phases in the bulk, were spread at the air-water interface. For both compounds, the surface pressure versus molecular area diagrams exhibit a large domain of molecular areas where the surface pressure of the film is quasi-constant. This plateau region of the isotherms corresponds to a transition from a monolayer in a liquid-expanded phase to a metastable condensed monolayer in which the molecules may adopt an "edge-on" arrangement. In this arrangement, the base of the pyramidic core is normal to the air-water interface. The film was also observed by means of fluorescence and polarizing microscopy. These techniques allowed us to show the formation of anisotropic slowly growing multilayered domains from the "edge-on" monolayer. An original method, based on the light reflectivity of the domains, was developed to measure their thickness and their optical anisotropy. The results show that these domains are formed by an arrangement of the molecules in rectilinear columns for one compound and in spiral columns for the other compound.

PACS
61.30 - 68.10G - 78.20

© Les Editions de Physique 1993