Surfactants in the Environment: Self-Assembly of PFAS Pollutants in Solution and at Interfaces

Surface active per- and polyfluoroalkyl substances (PFAS) find niche applications because of their high chemical and thermal stability, high interfacial activity, and incompatibility with both water and hydrocarbons. However, several widely used PFAS surfactants have been found extremely resistant to degradation, accumulate in the environment, and have long half-lives in humans, consequently generating great concern. Fundamental knowledge on PFAS surfactant properties and interactions supports the design of new materials to selectively capture and remove PFAS pollutants from aqueous media; also the reformulation of PFAS with non-fluorinated alternatives. To this end, we utilize complementary experiments (small-angle neutron scattering, SANS, with contrast variation) and modeling (molecular dynamics, MD), and present here examples on how the structure of micelles formed in water by perfluorooctanoate (PFOA) responds to the presence of various additives and polymers. Self-assembly into micelles reveals how PFAS surfactants interact with themselves and with water and other compounds present in solution. Micelles are relevant to PFAS environmental and health impacts in that PFAS surfactants, while typically found in very low bulk solution concentrations, they tend to accumulate on surfaces in the context of separations and biointerfaces.