Recent advances on synthesis of potentially non-bioaccumulable fluorinated surfactants

Fluorinated surfactants are exceptional compounds that have found many applications in everyday life. This review focuses on severe issues on the toxicity, persistency and bioaccumulation of these halogenated products, especially perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), the half-lives of which are several years in human serum. After an introduction on their productions, uses and hazards, this minireview updates non-exhaustive recent strategies of synthesis of original fluorosurfactants that may be potentially non-bioaccumulable. These routes have been devoted on: (i) the preparation of CF₃-X-(CH₂)_n-SO₃Na (with X = O, C₆H₄O or N(CF₃) and n = 8–12), (ii) the use of fluorinated polyethers (achieved either by oligomerization of hexafluoropropylene oxide (HFPO) or by ring opening cationic oligomerization of fluorinated oxetanes; (iii) the telomerization of vinylidene fluoride (VDF) with 1-iodoperfluoralkanes to produce C_nF_2n + 1-(VDF)₂-CH₂CO₂R (n = 2 or 4, R = H or NH₄), (iv) the radical telomerization of 3,3,3-trifluoropropene (TFP) with isoperfluoropropyliodide to prepare (CF₃)₂CF(TFP)_x-R_H, and (v) the radical cotelomerization of VDF and TFP, or their controlled radical copolymerization in the presence of either (CF₃)₂CFI or a fluorinated xanthate. In most cases, the surface tensions versus the surfactant concentrations have been assessed. These above pathways led to various highly fluorinated (but yet not perfluorinated) telomers or cooligomers, the chemical changes of which enabled to obtain original surfactants as novel alternatives to PFOA, ammonium perfluorooctanoate (APFO), or PFOS regarded as the PCBs of the XXIst century.