The incorporation of functional groups in the skeleton of vinylic addition polynorbornenes (VA-PNBs) is a difficult task due to the reluctant VA homo- and copolymerization of substituted norbornenes. We have found that copolymers of norbornene and alkenyl-norbornenes can be synthesized with good yields employing a-substituted benzylic complexes of palladium(II) as catalysts. The polymerization occurs exclusively through the endocyclic double bond and leaves the pendant double bond unaltered. Copolymers can be obtained with different compositions, richer in norbornene, and a different range of molecular weights depending on the catalyst used. The pendant double bond in these copolymers can be transformed by hydroboration or hydrosilylation reactions, leading to VA-PNBs with pendant polar groups not accessible either by direct polymerization or by post-polymerization functionalization reactions in an efficient way.
