Polymer-Induced Modifications in a Langmuir Monolayer PVP, we must first obtain a description of the polymer in the interfacial region under the conditions of our experiment. Since PVP has an affinity Recent experimental findings on the effect of a water soluble for the air-water interface, its concentration at the interface will be much nonionic polymer in the subphase on phase transformations in higher than its concentration in bulk water, which is in the dilute regime an insoluble monolayer of pentadecanoic acid ( PDA ) are disat 0.5%. Based on the analysis in a previous publication (6) we can say cussed. The experiments suggest that the influence of the polythat the polymer at the interface is in the so-called ''plateau regime'' of mer at large areas or low densities is primarily on the second the adsorption isotherm (8, 9). The adsorbed layer is composed of train virial coefficient of the surfactant monolayer. At high densities, segments that are in direct contact with the interface and a self-similar competition between attraction of the monomers for the bare network of loops and tails that extend from the surface to a distance equiva- surface of the air -water interface and repulsion from closely lent to the radius of gyration of the polymer (approximately 80 A ห). The packed PDA molecules results in displacement of the polymer train segments will occupy roughly half of the total available surface. Since from the interface.