Gemini cationic surfactants with flexible perfluorinated-ether chains.

• Gemini surfactants in some cases show higher surface activities than single-chain analogues. • Flexible perfluorinated-ether chains effectively modified gemini cationic surfactants. • Design of environmental friendly surfactants with low limiting surface tensions. This research aims at providing alternatives for long-chain fluorosurfactants, such as perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS) and their derivatives. Gemini quaternary ammonium fluorosurfactants with perfluorinated-ether chains were synthesized and their surface tensions were measured. The surface tensions at critical micelle concentration (γ cmc) are at the range of 14.7–23.3 mN/m and among them γ cmc of four perfluorinated-chain surfactants are below 16 mN/m.We found that the flexibility of perfluorinated-ether chains, such as CF 3 (OCF 2) n -, contributed significantly to enhance the surface activities. We also synthesized gemini cationic surfactants with C 6 F 13 CH 2 CH 2 - groups and their γ cmc are between 15.5 to 20.1 mN/m. Good linkage design, such as -(CH 2) n - (where n is odd), -CH 2 CH 2 OCH 2 CH 2 - and 1,2-phenylenebis(methylene), helps for lowering surface energy. The current research provides an approach for discovering non-bioaccumulative surfactants. [ABSTRACT FROM AUTHOR]