Fluoro (poly) ether group-containing silane compound

A fluoro(poly)ether group-containing silane compound represented by any of the formulae (B1), and (B2):

• Rf-PFPE—X3—SiRak1 (B1)
• Rak1Si—X3—PFPE—X3—SiRak1 (B2)
• wherein:
• Rf each independently at each occurrence represents an alkyl group having 1 to 16 carbon atoms which is optionally substituted by one or more fluorine atoms;
• -PFPE-X3— represents —(OC3F6)d—(OCF(CF3))—X10—CONH—X11—, or —(OC3F6)d—(OCF(CF3))—X10—(OR35)n4—X11—;
• —X3-PFPE-X3— represents —X11—NHCO—X10—(OC3F6)d—(OCF(CF3))—X10—CONH—X11—, or —X11—(R35O)n4—X10—(OC3F6)d—(OCF(CF3))—X10—(OR35)n4—X11—;
• wherein the repeating unit OC3F6 of the formula has a branched structure, and d is an integer of 2 or more and 200 or less;
• X10 is each independently at each occurrence a single bond or R36;
• R36 is a C1-20 alkylene group which is optionally substituted by one or more fluorine atoms;
• X11 is each independently at each occurrence a C1-20 alkylene group;
• R35 is each independently at each occurrence a C1-6 unsubstituted alkylene group;
• n4 is each independently at each occurrence an integer of 1 to 5;
• Ra each independently at each occurrence represents —Z3—SiR723;
• Z3 each independently at each occurrence represents C1-6 alkylene group;
• R72 each independently at each occurrence represents a hydroxyl group or a hydrolyzable group;
• k1 is 3.