Branched Fluoroether Ethyl Surfactants as Multi-Stage Degradable Platforms for Addressing the PFAS Dilemma

Fluorinated surfactants exhibit exceptional thermal and chemical stability under extreme conditions, yet escalating regulatory restrictions driven by their persistence and bioaccumulative potential have raised concerns regarding their future development. Although multiple design strategies have been proposed to address this issue, few have successfully resolved the intrinsic trade-off between high surface activity and environmental hazards. This study proposes a "multi-stage rocket" strategy incorporating branched fluoroether ethyl groups as cleavable units within fluorosurfactants. This design enables high surface activity during application while facilitating subsequent degradation into short-chain derivatives with a markedly reduced bioaccumulation potential. Compared to the commercial 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB), the new surfactants achieved surface tensions below 18 mN/m at similar critical micelle concentrations and demonstrated comparable foam formation and stability, supporting their applicability in aqueous film-forming foams. Photocatalytic degradation under UV/TiO₂ generated 66% perfluoro methoxy propionic acid (PMPA, C4) and 11% fluoroether carboxylic acid (C72CO₂H, C6), degradation products with significantly lower bioaccumulation profiles than bioaccumulative pollutants such as PFOS and PFOA (C8). Degradation pathway analysis elucidated the sequential transformation processes, reinforcing the mechanistic basis of the multi-stage design. This strategy offers a rational framework for developing fluorosurfactants with reduced bioaccumulation, advancing degradable alternatives to legacy perfluorinated pollutants.