Study enhances understanding of surfactant structure–property relationships
In a recent study by Andrew M. Bodratti et al. from the University of Buffallo, USA reported the aqueous self‐assembly behaviour of two homologous series of poly(ethylene oxide) (PEO)‐containing nonionic surfactants based on a C10‐Guerbet hydrophobe. Their study enhances the understaning of surfactant structure-property relationships.
Details of study
The two families of surfactants, alkyl ethoxylates and alkyl alkoxylates, are commercially available under the trade name “Lutensol” XP‐series and XL‐series, respectively. The latter incorporate propylene oxide (PO) units in the surfactant chain. Dye solubilization was used to determine the critical micellization concentration (CMC) of each surfactant at 22 and 50 °C. The PO‐containing alkyl alkoxylates displayed lower CMC values, which were also more sensitive to temperature. The Gibbs free energy, enthalpy, and entropy of micellization were computed from the CMC data and used to identify the contribution of each surfactant moiety (alkyl chain, PO unit, and PEO block) in controlling the CMC. The micellization properties are compared with compositionally similar surfactants with linear alkyl chains, yielding information about the effects of the Guerbet alkyl chain on micellization. Isothermal titration calorimetry was also used to characterize the CMC and enthalpy of micellization which generally compare well with the dye solubilization results. Cloud point data reveal nonmonotonic relationships for the surfactants with respect to composition, unlike linear alkyl chain surfactants. Finally, dilute solution viscosity measurements performed on some surfactants show a change in the slope, suggesting a structural change that tends to be more pronounced for surfactants with longer PEO blocks. The data presented herein enhance the understanding of surfactant structure–property relationships required for industrial formulation.
The complete article was published in Journal of Surfactants and Detergents on 22 April 2019