Exo-5-norbornene-2-carboxylic acid pentafluorophenyl ester was synthesized from 5-norbornene-2-carboxylic acid and polymerized by ring-opening metathesis polymerization. The obtained polymers were soluble polymeric active esters that could be used for the preparation of multifunctional polymers. The molecular weight of the polymers was controlled by variation of the monomer to initiator ratio. The precursor polymers reacted quantitatively with primary and secondary amines. Time resolved FT-IR studies at different temperatures of the polymer analogous reactions were performed and rate constants were determined.