The present invention relates to telechelic polymers having crosslinkable end groups of the formula and methods for preparing the same wherein n is an integer; is an alkadienyl group; Y is an alkyl group; and Z is crosslinkable end group. In general, the inventive synthesis involves reacting a functionalized chain transfer agent having crosslinkable ends with a cycloalkene in the presence of a ruthenium or osmium catalyst of the formula wherein: M is ruthenium or osmium; X and X1 are independently any anionic ligand; L and L1 are any neutral electron donor ligand; R and R1 are each hydrogen or a substituted or unsubstituted substituent wherein the substituent is selected from the group consisting of C1–C20 alkyl, C2–C20 alkenyl, C2–C20 alkynyl, aryl, C1–C20 carboxylate, C1–C20 alkoxy, C1–C20 alkenyloxy, C2–C20 alkynyloxy, aryloxy, C2–C20 alkoxycarbonyl, C1–C20 alkylthio, C1–C20 alkylsulfonyl and C1–C20 alkylsulfinyl. In another aspect of the invention, methods for controlling the molecular weight of the resulting telechelic polymer are also presented.