Polymers of formula Q-O-[A-B]z-[A-B′]z-A-Q′  (I) wherein: A=-(X)a—O-A′-(X′)b— with A′=perfluoropolyether chain and X, X′=—CF2—, —CF2CF2—; a, b=0.1 with the proviso that a=1 if A is linked to Q-O—; b=0 when A is linked to Q′; B derives from homopolymerizable olefins by radical route, of formula: —[(CR1R2—CR3R4)j(CR5R6—CR7R8)j′]—  (Ia) wherein j is an integer from 1 to 30, j′ is an integer from 0 to 29 with the proviso that (j+j′) is higher than 2 and lower than 30; R1-R8 are halogen; H; C1-C6 (per)haloalkyl; C1-C6 alkyl; or C1-C6 oxy(per)fluoroalkyl; B′=B but at least one among R1-R8 has a meaning different from that in B; z, z′ are such that the number average molecular weight of the polymer of formula (I) is between 500 and 150,000; Q, Q′=C1-C3 (per)fluoroalkyl or functional end group —(CFW)-Dq-Tk; W=F, CF3; k and q are integers, k ranges from 1 to 4, q is an integer and is equal to 0 or 1; with the proviso that at least one of Q, Q′ is functional end group.