n atoms; Rh has from about 4 to about 8 carbon atoms and is represented by the directional general formula .paren open-st.Cs H2s O.paren close-st.t Cr,H2r' --, wherein s is independently an integer of 3 to 7 for each (Cs H2s O), t is an integer of 1 to 2, and r' is an integer of 1; and Rf is a perfluoroether group represented by the formula --(Cx F2x O)z Cy F2y+1, where x is independently an integ