The behavior of aqueous systems containing block copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), coupled to hydrocarbon groups, was evaluated by differential scanning calorimetry (DSC). Endothermic transitions in the copolymer solutions were observed under a linear heating rate and the initial temperatures of these transitions are in agreement with the cloud points of the copolymers studied. Two transitions were observed in the cooling curves; these transitions were better defined at faster cooling rates of the copolymer solutions which can be related to the micelles formation. The effect of the increasing concentration of the hydrotropic agent, sodium p-toluenesulfonate (NaPTS), in the copolymer solutions was observed by the increase in the cloud points given by the dislocation of the endothermic peaks to higher temperatures.
Surfactants; copolymers; poly(ethylene oxide-b-propylene oxide); DSC; phase separation; micelles