AN INVESTIGATION OF MISCIBILITY IN GUEST-HOST MONOLAYERS BY SURFACE PRESSURE AND FLUORESCENCE METHODS

Abstract

The miscibility of the thermotropic liquid crystal dodecylcyanobiphenyl (12CB) in air-water monolayers of arachidic acid (AA) and oleic acid (OA) was studied by surface pressure and spectroscopic techniques. The mixing behavior was obtained from surface pressure-area isotherms by using the surface phase rule and excess area criterion. Results show that 12CB is immiscible in AA and miscible in OA over a wide range of compositions. These observations are confirmed by fluorescence emission spectroscopy. For the 12CB/AA system, the emission is due to 12CB excimer formation even at low mole fractions of 12CB, indicating immiscibility. In the case of 12CB/OA, the monomer emission is predominant at..