Fluorinated sulfonates are useful as surfactants in various applications. Commercially available fluorinated surfactants usually contain a perfluoroalkyl terminal chain. Honda, et al., in “Molecular Aggregation Structure and Surface Properties of Poly(fluoroalkylacrylate) Thin Films” Macromolecules (2005), 38(13), 5699-5705, disclose that a perfluoroalkyl chain of at least 8 carbons is necessary to maintain the perfluoroalkyl chains in a parallel orientation. For such perfluoroalkyl chains containing less than 8 continuous perfluorinated carbons, a reorientation occurs which decreases or eliminates the ability for exhibiting desirable surface properties. Thus longer perfluoroalkyl chains which contain a higher fluorine content at a given concentration typically provide better performance. However, the fluorinated materials derived from longer perfluoroalkyl chains are more expensive. Reducing the fluorine content with delivery of the same or better performance is therefore desirable.
U.S. Pat. No. 6,201,122, discloses a fluoroaliphatic radical-containing sulfonamido anionic compound, wherein the fluoroaliphatic radical group contains 3 to 20 carbons, and is preferably CnF2n+1 wherein n is 4 to 10. The compounds are useful as anionic surfactants in liquid systems. However, anionic surfactants are known to precipitate out of formulations commonly used in fire fighting applications and oilfield applications.
It is desirable to have surfactants containing partially fluorinated or shorter fully fluorinated terminal groups, or containing perfluoroalkyl chains interrupted with other atoms or moieties, to achieve equivalent or improved surface performance at lower expense. It is also desirable to have surfactants that do not precipitate out of end use formulations. The present invention provides such surfactants.