Surface and thermodynamic properties for some novel polyoxyalkylenated trimethylolpropane monoester surfactants

Three series of novel polyoxyethylenated trimethylolpropane (TMP) monoester surfactants have been synthesized and their molecular weights were evaluated experimentally by GPC. Also, their HLB values were determined from 1H NMR charts. The CMC's of the surfactants, obtained from surface tension measurements, are low in the order of 10−5 M. On the other hand, from surface tension-ln molar concentration plots, the minimum area/surfactant molecule (Amin) for the investigated surfactants were found to be increased with increasing the molecular weight of the incorporated ethylene oxide. The thermodynamic parameters of micellization (ΔGmic, ΔHmic and ΔSmic) and that for adsorption (ΔGad, ΔHad and ΔSad) were also calculated. The more negative Gibb's free energy of adsorption values than those of micellization suggest that these surfactants favor adsorption to micellization. This phenomenon is utilized for monitoring their corrosion inhibition efficiency and will be reported in a subsequent paper.