Synthesis and physiochemical properties of poly(ethylene glycol)-octanol sulfosuccinates

A series of sulfonated maleic diesters with ethylene oxide groups were synthesized by the reactions of esterification and sulfonation. Maleic diesters were prepared by esterification of maleic anhydride with any one kind of poly(ethylene glycol) with different molecular weights from 200 to 1000 and isooctanol, and then sulfonated by sodium bisulfite to get poly(ethylene glycol)-octanol sulfosuccinates. Reaction temperature and time of esterification of monoester and diester, using toluene sulfonic acid as catalyst and toluene as solvent, were investigated. The surfactants synthesized are identified by FTIR and 1HNMR. Thermal analysis results identify that the investigated surfactants have a good thermal stability. The surface activity of the surfactants in aqueous solution was determined at 298 K. It was found that the critical micelle concentrations (CMC) decrease with increase of the molecular weights and the number of ethylene oxide units of the investigated products, surface tension values at the CMC (γCMC) are upward trend in general. The maximum surface excess concentration (Γmax) decreases mildly with the increasing of molecular weight of poly(ethylene glycol), and area per molecule (Amin) increases with the increasing of ethoxy chain unit. Hydrodynamic diameter of investigated surfactants increases with increasing the concentration, and decreases in general trend with increase of molecular weight of poly(ethylene glycol). Addition of salt to the aqueous solution of surfactants sharply decrease values of CMC and γCMC compared with corresponded surfactants in distilled water.