New hydrofluoropolyethers II: Physico-chemical characterization

We obtained, through an original multi step synthetic approach with 60–80% selectivity, a novel family of hydrofluoropolyethers (HFPEs) characterized by a macromeric perfluoropolyether (PFPE) body end-capped, on one or both sides, by a 1,1-difluoroethoxy group. We synthesized these HFPEs trough an apparently conventional hydrogenation of PFPE precursors end-capped by reducible acyl halide groups and subsequent Cl cleavage by hydrogen, promoted by UV light in presence of hydrogen radical donor or by a metal catalytic system in presence of H2. The physico-chemical properties of these HFPEs were described and compared to those of similar perfluorinated or partially hydrogenated molecules, obtaining master curves of general validity when temperature dependent properties, like viscosity, were compared under temperature reduced condition. The contribution of the end-groups to the specific property, vanishing at a sufficient high molecular weight, was demonstrated more and more important at the lowest oligomerization degrees.