α‐sulfonated fatty acid esters: II. Solution behavior of α‐sulfonated fatty acid polyethylene glycol esters

Sodium α‐sulfonated, fatty acid polyethylene glycol monoesters [C m H 2 m +1 CH(SO 3 Na)COO(C 2 H 4 O) n H] and diesters [C m H 2 m +1 CH(SO 3 Na)COO(C 2 H 4 O) n COCH(SO 3 Na)C m H 2 m +1 ], where m =10–16 and n =1–35, were prepared by esterification of α‐sulfonated, fatty acids with polyethylene glycols, followed by neutralization with NaOH. Crude products were purified by reversed‐phase column chromatography on an octadecyl‐modified silica gel. Characteristic solution behavior of these α‐sulfonated fatty acid esters was, examined, and the following features were observed. All monoesters prepared in this work had Krafft points below 0°C and also possessed good calcium stabilities. Critical micelle concentrations of the monoesters increased monotonously, as a rule, with an increase in the number of oxyethylene units. These results suggest that the polyethylene glycol residue of the monoester behaves as a hydrophile. On the other hand, diesters possessed high water solubility, low foamability, and critical micelle concentrations that were lower by a factor of ten compared to those of the monoesters.