PHASE-SEPARATION IN CONCENTRATED MIXTURES OF POLYMERS AND SURFACTANTS

The phase behaviour of concentrated mixtures of non-ionic polymers and surfactants has been studied and compared with a simple theory for depletion of polymers from the surface of a colloidal particle. In systems where there is no association between the polymer and surfactant, phase separation occurs to give polymer-rich and surfactant-rich phases. Where there was an initial association between the polymer and surfactant, separation occurred at higher concentrations. The phase separation has been treated as depletion flocculation, a theory for which gives the approximate distributions of polymer and surfactant in each phase. The effects of temperature, electrolyte and hydrocarbon chain length of the surfactant can be understood by comparison with their effects on the cloud points of the pure surfactants.