Compounds of the formulae, (IIa) or (IIb) Z n SpacerX x where Z = R f -CHF-CF 2 -Y-(CH 2) m - or R f -O-CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF 2) 1-4 -CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF 2) 1-4 -O-CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF(CF 3)-CF 2) 1-4 -CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF(CF 3)-CF 2) 1-4 -O-CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF 2 -O) 1-4 -CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF 2 -CF 2 -O) 1-4 -CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF 2 -O) 1-4 -(CF 2 -CF 2 -O) 1-4 -CHF-CF 2 -Y-(CH 2) m -, n = 2 or 3, Rf = CF 3 -, CF 3 -CF 2 - or CF 3 -CF 2 -CF 2 -, Y = O or S, m = 0 or 1, spacer = a saturated, branched or unbranched hydrocarbon unit, in which one or more non-adjacent C atoms may be replaced by O or N, X is one of the groups -SO 3 -, -OSO 3 -, -COO -, -PO 3 2- or OPO 3 2-, polyethylene glycol or polypropylene glycol, -CH -CH 2 -NH-sach, -Y-(CH 2 -CH 2 -O) v -R 4, betaines or sulfobetaines, where sach = various sugars and Y = S, O or NH, preferably O, R 4 = H or alkyl, preferably H or CH 3, and v = 1=100, preferably 1-30, x = 1, [F(CF 2) n' o CHF-CF 2 -Y-(CH 2) m] 2 Spacer-X formula (IIa) [F(CF 2) n' o -(CF 2) 1-4 -O-CHF-CF 2 -Y-(CH 2) m] 2 Spacer-X formula (IIb) where n' = 1-6, m = 0 or 1, o = 0 or 1, Y = O or S, and the group (spacer-X) = CR 5 (CH 2) n" OH, CR 5 (CH 2) n" SH, CR 5 (CH 2) n" COOH, CR 5 (CH 2) n" SO 3 H, CR 5 (CH 2) n" NH 2, CR 5 (CH 2) n" NR' 2, CR 5 (CH 2) n" N + (CH 3) 3 Cl -, CR 5 (CH 2) n" NR' 2 -CH 2 -COO -, CR 5 (CH 2) n" O(CHR a -CHR b O) n R", CR 5 (CH 2) n" S(CHR a -CHR b O) n R" or CR 5 (CH 2) n" NH(CHR a -CHR b O) n R", n" = 0 or 1, n = 1-30, and R 5, R', R", R a and R b independently of one another = H or alkyl, and where all indices are selected so that no O-O bonds are present. Z = R f -CHF-CF 2 -Y-(CH 2) m - or R f -O-CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF 2) 1-4 -CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF 2) 1-4 -O-CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF(CF 3)-CF 2) 1-4 -CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF(CF 3)-CF 2) 1-4 -O-CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF 2 -O) 1-4 -CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF 2 -CF 2 -O) 1-4 -CHF-CF 2 -Y-(CH 2) m - or R f -O-(CF 2 -O) 1-4 -(CF 2 -CF 2 -O) 1-4 -CHF-CF 2 -Y-(CH 2) m -, n = 2 or 3, Rf = CF 3 -, CF 3 -CF 2 - or CF 3 -CF 2 -CF 2 -, Y = O or S, m = 0 or 1, spacer = a saturated, branched or unbranched hydrocarbon unit, in which one or more non-adjacent C atoms may be replaced by O or N, X is one of the groups -SO 3 -, -OSO 3 -, -COO -, -PO 3 2- or OPO 3 2-, polyethylene glycol or polypropylene glycol, -CH -CH 2 -NH-sach, -Y-(CH 2 -CH 2 -O) v -R 4, betaines or sulfobetaines, where sach = various sugars and Y = S, O or NH, preferably O, R 4 = H or alkyl, preferably H or CH 3, and v = 1=100, preferably 1-30, x = 1, where n' = 1-6, m = 0 or 1, o = 0 or 1, Y = O or S, and the group (spacer-X) = CR 5 (CH 2) n" OH, CR 5 (CH 2) n" SH, CR 5 (CH 2) n" COOH, CR 5 (CH 2) n" SO 3 H, CR 5 (CH 2) n" NH 2, CR 5 (CH 2) n" NR' 2, CR 5 (CH 2) n" N + (CH 3) 3 Cl -, CR 5 (CH 2) n" NR' 2 -CH 2 -COO -, CR 5 (CH 2) n" O(CHR a -CHR b O) n R", CR 5 (CH 2) n" S(CHR a -CHR b O) n R" or CR 5 (CH 2) n" NH(CHR a -CHR b O) n R", n" = 0 or 1, n = 1-30, and R 5, R', R", R a and R b independently of one another = H or alkyl, and where all indices are selected so that no O-O bonds are present.