STUDY OF THE SURFACE-TENSION OF POLYMER-SOLUTIONS - THEORY AND EXPERIMENTS IN THETA SOLVENT CONDITIONS

A study of the surface tension of semi-dilute polymer solutions in theta solvent conditions is presented. Theoretical predictions are given for the two cases when the interface is attractive or repulsive. The Cahn approach for the interfacial tension is used in order to calculate the interfacial tension in the mean field theory of polymer solutions. The measurements, were performed on two polymer theta solvent systems: polydimethysiloxane-bromocyclohexane at 29 degree C and polystyrene-cyclohexane at 34 degree C for the attractive and repulsive cases respectively. The well-known ring method was used. The agreement between theory and experiments is good. The theoretical predictions and the results are compared with those obtained in good solvent case that the authors reported in a previous paper. The transition theta solvent-good solvent is studied for the attractive system.