Phase behavior of nonionic surfactant solutions in the presence of polyvinylpyrrolidone

The phase separation behavior of four nonionic polyoxyethylene alkyl ether surfactants was examined in aqueous solutions containing polyvinylpyrrolidone (PVP) of various molecular weights. It was found that PVP decreases the cloud point (CP) and increases the Krafft point (KP) of the surfactants. The decrease in CP is dependent on the concentration of PVP, the molecular weight of PVP, and the structure of the surfactant hydrophobic group. The increase in KP is only dependent on PVP concentration. The effect of PVP on the CP and KP of these surfactants is smaller than that of PEG of the same nominal molecular weight.