Compounds having the following formula: wherein: A and A1, equal or different, are respectively H or an aromatic end group as defined below; optionally said aromatic group being substituted; n is an integer different from zero, such that the number average molecular weight of the compound of formula (I) is in the range 1,800-50,000, T is the bivalent group —Y—CH2—CFW1—O—Rf—CFW2—CH2—Y— wherein: Y=O, S; W1 and W2, equal or different, are F, CF3; Rf is a (per) fluoropolyoxyalkylene chain formed of one or more repeating units, statistically distributed along the chain; R1, R2, R3, equal to or different from each other, are selected from H; linear or branched C1-C8 perfluoroalkyl, linear or branched C1-C15 (per) fluorooxyalkyl; linear or branched C1-C8 alkyl; linear or branched C1-C8a oxyalkyl, optionally containing one or more oxygen atoms; NO2; CN.