2024 AIChE Annual Meeting
(393k) An Analysis of Fluorinated and Fluorine-Free Surfactants at Interfaces: Insights from Ab Initio and Molecular Dynamics Simulations.
Per- and poly-fluoroalkyl substances (PFAS) constitute a class of synthetic compounds with exceptional interfacial properties. Their widespread use in many industrial applications and consumer products, combined with their remarkable chemical and thermal stability, has led to their ubiquitous presence in environmental matrices, including surface and groundwater. Mounting evidence shows their accumulation in the biological tissues of both humans and animals. To design better fluorine-free chemical alternatives, it is necessary to develop a deep molecular-level understanding of the mechanisms responsible for the exceptional properties of PFAS. Although molecular simulations, combined with experiments, are promising for uncovering these mechanisms, the reliability of simulation results depends strongly on the accuracy of the force fields implemented. At the moment, atomistic force fields are not available to describe PFAS in a variety of environments. Ab initio methods could help fill this knowledge gap, but they are computationally demanding. As an alternative approach, ab initio calculations could be used to develop accurate force fields for atomistic simulations.
In this work, atomistic force fields were developed for perfluorinated sulfonic and perfluoroalkyl acids, building on ab initio simulation results. The accuracy of the new force fields was benchmarked against solvation-free energy and interfacial tension data. The new force fields were then used to probe the interfacial behavior of PFAS surfactants. Both thermodynamic and structural interfacial properties were calculated. To help understand why PFAS sometimes outperforms non-fluorinated chemicals, the PFAS interfacial properties observed in our simulations were compared against those manifested by different fluorine-free surfactants. The good agreement achieved with experiments suggests that the proposed protocol could be implemented to study other perfluorinated substances.
In this work, atomistic force fields were developed for perfluorinated sulfonic and perfluoroalkyl acids, building on ab initio simulation results. The accuracy of the new force fields was benchmarked against solvation-free energy and interfacial tension data. The new force fields were then used to probe the interfacial behavior of PFAS surfactants. Both thermodynamic and structural interfacial properties were calculated. To help understand why PFAS sometimes outperforms non-fluorinated chemicals, the PFAS interfacial properties observed in our simulations were compared against those manifested by different fluorine-free surfactants. The good agreement achieved with experiments suggests that the proposed protocol could be implemented to study other perfluorinated substances.