Addition polymerization of dicyclopentadiene: reactivity of endo and exo isomers and post-modification

The polymerization of dicyclopentadiene (DCPD, mixture of endo and exo isomers), 9,10-dihydrodicyclopentadiene (H-DCPD), exo-DCPD and endo-DCPD mediated by TiCl4/Et2AlCl was systematically studied. Oligomers containing 2,3-enchainement units, rearranged 2,7 units, and a low amount of fully saturated nortricyclene units were essentially obtained in good yields. The microstructure of the obtained oligomers and polymers strongly depends on the type of monomer and the polymerization conditions, namely the monomer feedstock concentration and the type of solvent. The endo-DCPD isomer was less reactive than the exo isomer, while it exhibited a reactivity comparable with that of the partially saturated H-DCPD. However, while all the products obtained from the polymerization of the exo isomer and H-DCPD were amorphous, from the endo isomer we obtained: (i) at low DCPD/Ti ratio, a crystalline, stereoregular tetramer having a 2,3-exo-disyndiotactic structure, and (ii) at high DCPD/Ti ratio, a product constituted of different fractions consisting of amorphous oligomers, and a crystalline polymer with 2,3-, 2,7- and nortricyclene units. The results show that the bent shape of the cyclopentene, the presence of the double bond in the cyclopentene ring and the polymerization conditions play a fundamental role in driving the reaction toward the formation of unique crystalline materials. Finally, hydrogenation and epoxidation of the obtained DCPD products were carried out. All the materials were characterized by FTIR, 1H- and 13C- NMR, SEC, XRD and TGA.