SURFACE ACTIVITY OF FLUORINATED ORGANIC COMPOUNDS AT ORGANIC-LIQUID/AIR INTERFACES PART III - EQUATION OF STATE OF ADSORBED MONOLAYERS AND WORK OF ADSORPTION OF A FLUOROCARBON GROUP

摘要

Previous investigations have demonstrated that a wide variety of partially fluorinated carboxylic esters are capable of adsorbing as unimolecular films at the interfaces between various organic liquids and air, and also that these films are usually in a gaseous or otherwise expanded state. In the present study it is shown that isotherms of film pressure (F) vs area (A) per adsorbed molecule of solute, at large values of A, obey the simple equation of state (F + F0) (A - A0) = KT. However, as the film pressures increase, the deviation from this equation increases. The two-dimensional analog of the van der Waals equation (F + a/A2) (A - A„) = kT, which includes a more definitive correction factor for the inter-molecular attraction between neighboring molecules in the film, was in good agreement with the experimental data even at very low areas per molecule.