We describe the synthesis of a new type of linear polycationic polynorbornane by vinylic polymerization in water of an ammonium norbornene as monomer. This polymerization catalyzed by PdCl2 leads to stretched flexible polymers able to complex DNA. Moreover the complexes obtained are stable, protecting DNA from DNAse enzymatic degradation. Finally the first transfection assays showed that this new polymer is able to mediate transfection in target COS cells.