Abstract
Commercial fatty-acid-ester-type surfactants are usually mixtures of mono- and di- (or poly) esters and unreacted hydrophilic moieties such as polyethyeneglycol (PEG). Their phase behavior is influenced by by-products. The phase behavior of commercial decaoxyethylene glycol dodecanoate ester (C11EO10 (E)) in water and in water-oil systems was compared with that of commercial decaoxyethylene dodecyl ether (C12EO10). No liquid crystalline phase was formed at any concentration in the water/C11EO10 (E) system. The cloud temperature of C11EO10 (E) was found to be 46°C, this being for less than that of C12EO10, 89°C, although the average EO- chain length surfactant of these is the same. The phase behavior of C11EO10 (E) in water was not significantlly influenced by PEG in a dilute region. The low cloud temperature may essentially have been due to the presence of diester. HLB temperature in either surfactant system was basically the same on using, when m-xylene, decane, and cyclohexane as oils. The diester dissolved in the presence of oil, and HLB temperature increased in the C11EO10 (E) system when the surfactant aggregates contained much monoester. This explains why HLB temperature in either surfactant system was essentially the same.
