Synthesis of Crystalline CF3 -Rich Perfluoropolyethers from Hexafluoropropylene Oxide and (Trifluoromethyl)Trimethylsilane.

Abstract

The synthesis of a CF3 -rich perfluoropolyether (PFPE) is achieved via the fluoride-catalyzed reaction of hexafluoropropylene oxide (HFPO) with (trifluoromethyl)trimethylsilane (TMSCF3 , so-called Ruppert-Prakash reagent). Nucleophilic addition of a CF3 anion to HFPO affords an acyl fluoride via the ring-opening of HFPO, followed by fluoride elimination. Further addition of CF3 anions to the acyl fluoride gives tertiary perfluoroalkoxide, which attacks HFPO to regenerate an acyl fluoride. Repetition of the sequence via substitution-polymerization affords a new PFPE as a solid, whose structure was confirmed using 19 F NMR spectroscopy, GC-MS, and MALDI-TOF MS analysis. Thermal and X-ray diffraction analyses revealed a crystalline character. To the best of our knowledge, this is the first example of crystalline PFPE. Based on contact-angle measurements, the critical surface tension of this solid PFPE (13.4 mN m-1 ) suggests a water- and oil-repellency of this CF3 -rich PFPE that is higher than that of polytetrafluoroethylene (PTFE; 18.5 mN m-1 ).