The surface tension of polymer liquids

A brief review of the surface tension of polymer liquids is presented. A st rong emphasis is placed on recent measurements of surface tensions of homol ogous liquid series up to high-molecular-weight polymers, and the thermodyn amic liquid properties of these same homologous series obtained from source s such as pressure-volume-temperature (PVT) data. The accuracy and limitati ons of the thermodynamic information which are used as input to many of the theories applied to the surface properties of polymer molecules are discus sed. By scaling the surface tension data using a true measure of the cohesi ve energy density of the liquid state, we can clearly observe the entropic contribution to the surface tension caused by the conformational restrictio n of a large molecule at the liquid-vapor interface. The scaling implies th e existence of a corresponding states principle for both polymer liquids an d for low-molecular-weight liquids. The ramifications of the existence of a corresponding states principle for the surface tension of polymer melts ar e discussed. One consequence of the corresponding states principle is that it allows us to use surface tension measurements to compute the cohesive en ergy density of polymer melts using PVT data.