F1 is formula (IIa) and F2 is formula (IIb): g and d are 0, 1, 2 or 3; R14 and R15 are C1-C4 or a cyclohexyl radical; R1 to R12 represents hydrogen or alkyl with 1 to 22 carbon atoms; x and y are integers, x+y is 0 to 2; R13 is oxygen or sulphur or divalent —CH2— n1, n2, m, p1 and p2 are an integer or equal to 0 and such that the molecular weight Mn of the polymer of formula (I) is between 400 and 100 000 g/mol; a process for preparation of the polymer; and use as adhesive in mixture with an amino compound with at least two amine groups.