Formation and properties of Langmuir and Gibbs monolayers: a comparative study using hydrogenated and partially fluorinated amphiphilic derivatives of mannitol

The synthesis and surface behavior of a series of nine new hydrogenated non ionic surfactants and their fluorinated analogs, derived from D-mannitol ar e described. Adsorption monolayers (Gibbs monolayers) were studied by surfa ce pressure (II) measurements as a function of time. For the spread monolay ers (Langmuir monolayers), the measurements of surface pressure versus mole cular area (A) were performed. For the most hydrophobic amphiphiles at low concentrations, the adsorption at the air/water interface from the bulk sol ution required extremely long times to attain equilibrium. The A values for two compounds which could be studied in both adsorbed and spread monolayer s provided data allowing a direct comparison of the properties of the two t ypes of films formed at the air/water interface. In spite of different mech anisms of formation of Langmuir and Gibbs monolayers, their characteristic parameters were identical, proving the equivalence of these two types of st ructures. (C) 2000 Published by Elsevier Science Ireland Ltd. All rights re served.