PHASE-BEHAVIOR OF AQUEOUS-SOLUTIONS CONTAINING NONIONIC SURFACTANT POLYETHYLENE-GLYCOL MIXTURES

The phase separation behavior of two nonionic surfactants, polyoxyethylene (10) oleyl ether (I) and polyoxyethylene (10) cetyl ether (II), was examined in solutions containing polyethylene glycols (PEGs) of various molecular weights. It was found that PEGs decrease the cloud points of both surfactants, and that this decrease is dependent upon the concentration and molecular weight of the PEG. This effect of PEGs on the cloud point can be explained by a depletion flocculation mechanism, which results in a segregative phase separation of the solution into surfactant-rich and polymer-rich phases. The Krafft point of II increased in the presence of PEGs, and this increase was dependent on the concentration of PEG, but independent of its molecular weight.