Cross-linkable compounds comprising a perfluoropolyether moiety

A cross-linkable compound comprising a perfluoropolyether (PFPE)-containing moiety which is ultimately terminated by an oxygen atom and bonded through a spacer attached to the said oxygen atom with an ethylenically unsaturated group, wherein the spacer extends linearly over at least three atoms in a row between the oxygen atom and the ethylenically unsaturated group, said cross-linkable compound having the formula

• D—(CnF2nO)m—Q—B—A, wherein
• A stands for an ethylenically unsaturated group selected from the group consisting of HR1C═CR2— and HR1C═CR2Si(R4)2—, wherein R1 is selected from H, alkyl, phenyl, alkyl-substituted phenyl and aralkyl;
• R2 is selected from H, alkyl, phenyl, alkyl-substituted phenyl and aralkyl and R4 being independently H or alkyl;
• B stands for a hydrocarbyl or fluorocarbyl spacer extending over at least three carbon atoms;
• (CnF2nO)m is the PFPE moiety wherein n1 is independently an integer of 1 to 4 and m is an integer of 2 to 500;
• Q stands for a bivalent group selected from —CF2—CH2—O—and —CH2—CH2—O—;
• and
• D stands for HO—CH2CF2—O— or A—B—Q—O—, wherein n, A, B, and Q have the previously given meanings.