A polymer [polymer P] comprising: - at least one (per)fluoropolyether chain [chain (R pf)] and - at least two chains [chains (R e)] bonded to opposite sides of said chain (R pf), wherein at least one chain (R e) comprises a branched alkyl chain interrupted by at least two oxygen atoms [chain (C o)], and two or more alkoxy-silane groups [groups (Si)], wherein said chain (R pf) is a chain of formula: - a O(R f)(CFX') b - wherein a and b, equal or different from each other, are equal to or higher than 1, preferably from 1 to 10, more preferably from 1 to 3; X and X', equal or different from each other, are -F or -CF 3, provided that when a and/or b are higher than 1, X and X' are -F; (R f) is selected from chains of formula: (Rf-IIA) -[(CF 2 CF 2 O) a1 (CF 2 O) a2]- wherein: - a1 and a2 are independently integers ≥ 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; both a1 and a2 are preferably different from zero, with the ratio a1/a2 being preferably comprised between 0.1 and 10; (R f -IIB) -[(CF 2 CF 2 CF 2 O) b]- wherein: - b is an integer > 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; (R f -IIC) -[(CF 2 CF 2 CF 2 CF 2 O) c]- wherein: - c is an integer > 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; (R f -IID) -[(CF 2 CF 2 O) d1 (CF 2 O) d2 (CF(CF 3)O) d3 (CF 2 CF(CF 3)O) d4]- wherein: d1, d2, d3, d4, are independently integers ≥ 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; preferably d1 is 0, d2, d3, d4 are > 0, with the ratio d4/(d2+d3) being ≥1; (R f -IIE) -[(CF 2 CF 2 O) e1 (CF 2 O) e2 (CF 2 (CF 2) ew CF 2 O) e3]- wherein: ew = 1 or 2; e1, e2, and e3 are independently integers ≥ 0 chosen so that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; preferably e1, e2 and e3 are all > 0, with the ratio e3/(e1+e2) being generally lower than 0.2; said at least one chain (R e) comprising said chain (C o) and said groups (Si) being free from functional groups selected from amino groups, amido groups, ester groups, keto groups, urethane groups, and siloxane groups, and being linked to chain (R pf) via group selected from -CH 2 -O-, -CH(CF 3)-O- and -CH 2 (OCH 2 CH 2) n -O- wherein n is an integer from 1 to 15; and said chain (C o) complies with one of the following general structures (C o -I) to (C o -VI): wherein the symbol (*) indicates the bond with said chain (R pf) and the symbol (#) indicates the bond with said group (Si). - at least one (per)fluoropolyether chain [chain (R pf)] and - at least two chains [chains (R e)] bonded to opposite sides of said chain (R pf), wherein at least one chain (R e) comprises a branched alkyl chain interrupted by at least two oxygen atoms [chain (C o)], and two or more alkoxy-silane groups [groups (Si)], a and b, equal or different from each other, are equal to or higher than 1, preferably from 1 to 10, more preferably from 1 to 3; X and X', equal or different from each other, are -F or -CF 3, provided that when a and/or b are higher than 1, X and X' are -F; (R f) is selected from chains of formula: (Rf-IIA) -[(CF 2 CF 2 O) a1 (CF 2 O) a2]- - a1 and a2 are independently integers ≥ 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; both a1 and a2 are preferably different from zero, with the ratio a1/a2 being preferably comprised between 0.1 and 10; (R f -IIB) -[(CF 2 CF 2 CF 2 O) b]- - b is an integer > 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; (R f -IIC) -[(CF 2 CF 2 CF 2 CF 2 O) c]- - c is an integer > 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; (R f -IID) -[(CF 2 CF 2 O) d1 (CF 2 O) d2 (CF(CF 3)O) d3 (CF 2 CF(CF 3)O) d4]- ew = 1 or 2; e1, e2, and e3 are independently integers ≥ 0 chosen so that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; preferably e1, e2 and e3 are all > 0, with the ratio e3/(e1+e2) being generally lower than 0.2; said at least one chain (R e) comprising said chain (C o) and said groups (Si) being free from functional groups selected from amino groups, amido groups, ester groups, keto groups, urethane groups, and siloxane groups, and being linked to chain (R pf) via group selected from -CH 2 -O-, -CH(CF 3)-O- and -CH 2 (OCH 2 CH 2) n -O- wherein n is an integer from 1 to 15; and said chain (C o) complies with one of the following general structures (C o -I) to (C o -VI): wherein the symbol (*) indicates the bond with said chain (R pf) and the symbol (#) indicates the bond with said group (Si).