Synthesis and performance of a Mono (dodecafluoroheptyl) acetate surfactant

The influence of molecular structure on PFAS adsorption at air-water interfaces in electrolyte solutions

Fluid-fluid interfacial adsorption has been demonstrated to be an important retention process for per and polyfluoroalkyl substances (PFAS) in porous media with air or non-aqueous phase liquids (NAPLs) present. The objective of this study was to characterize the influence of PFAS molecular structure on air-water interfacial adsorption in electrolyte solutions. Measured and literature-reported surface-tension data sets were aggregated to generate the largest compilation of interfacial adsorption coefficients measured in aqueous solutions comprising environmentally representative ionic strengths. The surface activities and interfacial adsorption coefficients (Ki) exhibited chain length trends, with greater surface activities and larger Ki values corresponding to longer chain length. The impact of multiple-component PFAS solutions on the surface activity of a select PFAS was a function of the respective surface activities and concentrations. Quantitative structure-property relationship analysis (QSPR) employing a single molecular descriptor (molar volume) was used successfully to characterize the impact of PFAS molecular structure on air-water interfacial adsorption. A previously reported QSPR model based on PFAS data generated for deionized-water solutions was updated to include more than 60 different PFAS, comprising all head-group types and a wide variety of tail structures. The QSPR model developed for PFAS in electrolyte solution compared favorably to the model developed for deionized water. Additionally, the magnitude of ionic strength for non-zero ionic strength systems was determined to have relatively minimal impact on interfacial adsorption coefficients. The new QSPR model is therefore anticipated to be representative for a wide variety of PFAS and for a wide range of ionic compositions.

Preparation and Insights of Smart Foams with Phototunable Foamability Based on Azobenzene-Containing Surfactants

Smart foams with tunable foamability exhibit superb applications in many fields such as colloidal and interface science. Herein, we have synthesized an azobenzene-containing surfactant with excellent photoresponsiveness by a simple thiol-maleimide click reaction between thioglycolic acid and 4-(N-maleimide) azobenzene (MAB). The structure and the photoresponsive behavior of the novel surfactant are characterized. Depending on the solution concentration, the synthesized surfactant demonstrated various speeds for the trans/cis photoisomerization varying from 9 to 24 s for the given concentration range and excellent reversible photoisomerization cycling stability (more than 20 cycles) upon light irradiation. Based on these conformational switches, a series of phototriggered obvious surface properties (e.g., critical micelle concentration (CMC), surface tension (γ), and surface excess concentration (Γ)) changes of the surfactant are achieved. More specifically, the smart foam system with tunable foamability is realized. As-formed smart foams with rapid photocontrolled reversible foaming/defoaming transition and excellent cycling stability make them very attractive candidates for applications in wastewater treatment, green textile, oil extraction, and emulsification.