The cationic polymerization of “endo” ‐dicyclopentadiene, 1,2–dihydro‐“endo” ‐dicyclopentadiene and 9,10–dihydro‐“endo” ‐dicyclopentadiene

The polymerizations of “endo” ‐dicyclopentadience (I), 1,2–dihydro‐“endo”‐dicyclopentadiene (II) and 9,10–dihydro‐“endo”‐dicyclopentadiene (III), initiated by cationic systems, have been investigated under different conditions. Linear polymers with M̄n in the range 1300–4500 have been obtained with (I) and (II): poly‐(I) shows less than one double bond for structural unit. In the case of (III) only oligomers were observed. Copolymerization runs show a reactivity of (III) lower than (II). Spectroscopic and chemical analyses of the polymers obtained indicate that besides the norbornene double bond, also the cyclopentenic unsaturation, present in (I) and (III), reacts. Some evidences for a hydride shift in cyclopentence ring, after the attack of the initiator, were collected. In the case of poly‐(I) the main enchainment resulted from the norbornene double bond opening, but about 30% of nortricyclene repeating unit was also observed.