Evaluation of alkyl sulfate and sulfonate micellar structure at the water–surfactant interphase with simple geometrical calculations

The present work deals with an interpretation of the differences in micellar structure of two surfactants, sodium decyl sulfonate and sodium decyl sulfate, whose only difference in molecular structure is the presence, for sulfate, of an oxygen atom bridging alkyl chains from a common SO3- charged head group. Using a simple geometrical approach, a different exposure of the surfactant head groups on the micellar surface is proposed. It is also shown that the different interphase microstructure could be the reason that decyl sulfate forms ellipsoidal aggregates, in contrast to decyl sulfonate, which forms nearly spherical micelles.

Graphical abstractThe different exposure of the surfactant’ headgroups on the micellar surface could be the origin of the tendency of sodium decylsulfate to form ellipsoidal aggregates, whereas for sodium decylsulfonate nearly spherical micelles are preferentially.Figure optionsDownload full-size imageDownload high-quality image (142 K)Download as PowerPoint slideResearch highlights► Simple geometrical consideration allows analysis of micellar microstructure. ► The orientation of sulfate and sulfonate head groups on the micelle surface is different. ► The shape of alkyl sulfate and sulfonate micelles is different.