DYNAMIC SURFACE ELASTICITY OF POLYMER-SOLUTIONS

The surfaces of surfactant solutions exhibit viscoelastic dilational b ehavior which may be investigated by modern optical and mechanical met hods. The present study focuses on the dynamic dilational properties o f the polymer solution - gas interface. Linear flexible polymer chains at the surface are considered as consisting of ''trains,'' lying on t he surface, and ''loops'' and ''tails'' that protrude into the liquid. The Rouse model is used to describe the inner dynamics of the trains, whereas their motion relative to their neighbors on the surface can b e described with the help of the reptation conception. An expression f or the complex dynamic dilational surface elasticity has been derived. Although, in general, the relaxation of the surface tension is charac terized by an infinite series of relaxation times, it is shown that fo r many systems the dynamics of the surface layer can be described appr oximately by only two main relaxation times. The dispersion equation, which was obtained earlier for solutions of conventional surfactants, is shown to be fulfilled for polymer solutions also.