Effects of the Polypropylene Oxide Number on the Surface Properties of a Type of Extended Surfactant

Abstract

The surface properties of 5 extended surfactant C12–14P mE2S solutions in pure water and 0.1 M NaCl were investigated through surface tension and electrical conductivity measurements. The surface properties measured include the critical micelle concentration (CMC), critical surface tension (γcmc), maximum surface excess concentration (Γmax), minimum area occupied per surfactant molecule (Amin), and efficiency in surface tension reduction (pC20). The CMC values of the 5 surfactants decreased with increasing polypropylene oxide number (PON) and were higher than those obtained in 0.1 M NaCl. The Γmax values showed a downward trend whereas the Amin values exhibited an upward trend with increasing PON without NaCl. The Γmax values were higher and the Amin values were lower than those obtained without 0.1 M NaCl. The CMC values increased at elevated temperatures. The CMC values of C12–14P3E2S, C12–14P5E2S, and C12–14P8E2S were similar but were markedly lower than those of C12–14E2S at different temperatures. When PON was less than 12, the log CMC value decreased linearly with increasing PON in the absence of salt, and the relationship between pC20 and PON was linear. But in the presence of 0.1 M NaCl, the log CMC value decreased exponentially with increasing PON.

Extended Surfactants Including an Alkoxylated Central Part Intermediate Producing a Gradual Polarity Transition—A Review of the Properties Used in Applications Such as Enhanced Oil Recovery and Polar Oil Solubilization in Microemulsions

“…It can be seen from Table data that the introduction of a few PO units considerably decreases the CMC, and increases the adsorption area per molecule, (in part because of the methyl branching of PO) and increases the surfactant tail length. Other recent studies confirmed these data (Lv et al, ).…”

“…This CMC phenomenon was found to also happen with the extended surfactants too, and to vary, not only with the tail, but also with different PON intermediates and head groups. (Charoensaeng et al, ; Fernandez et al, , b; Forgiarini et al, ; Goethals et al, ; Klaus et al, ; Lv et al, ; Miñana‐Pérez, ; Scorzza et al, , b; Witthayapanyanon et al, ).…”

“…The CMC is found to decrease as the number of polypropylene oxide (PON) groups increases in the intermediate part (Lv et al, ; Miñana‐Pérez et al, ; Scorzza et al, ). This means that the PO groups must be included in the hydrophobic part.…”

Extended surfactants and their tailored applications for vegetable oils extraction: An overview

“…The CMC is the concentration of surfactants in a solution above which micelles form. As shown in Table 2, the addition of extension (PO or EO) units into a surfactant molecule generally decreases the CMC (He et al, 2014;Liu et al, 2016a, b;Lv et al, 2018). For instance, Liu et al (2016a, b) have observed a decrease in CMC from 8.2 mmol.L À1 for the conventional SDS (C 12 -Sulfate) to 0.42 mmol.L À1 for C 12 -PO 4 -Sulfate (addition of 4 PO units) and down to 0.043 for C 12 -PO 12 -Sulfate (addition of 12 PO units).…”

“…Beyond that point, structural variations such as the addition of an extension structure into a surfactant molecule impact its surface properties. In particular, this modifies molecular interactions at the interface, and thus affects the two main Lv et al (2018).…”