Terpolymerization of Substituted Cycloolefin with Ethylene and Norbornene by Transition Metal Catalyst

Ethylene-norbornene terpolymerization experiments using 5-alkyl-substituted norbornenes (5-pentyl-2-norbornene (C₅N) and 5-octyl-2-norbornene (C₈N)) or dicyclopentadiene (DCPD) were conducted with two ansa-metallocenes, [Zr{(η⁵-C₉H₆)₂C₂H₄}Cl2] (1) and [Zr{(η⁵-2,5-Me₂C₅H₂)₂CHEt}Cl₂] (2), activated by methylaluminoxane (MAO). The terpolymers obtained were investigated in detail by determining the microstructure and termonomer contents by ¹³C NMR, molar masses and thermal properties. Results were compared to those of ethylene (E)-norbornene (N) terpolymerizations with 1-octene. 2, with lower steric hindrance and a shorter bridge, gave the best activities, termonomer incorporation and molar masses. The size of the substituent in 5-alkyl substituted norbornene also plays a role. C₈N gives the highest activities and molar masses, while DCPD terpolymers have the highest cycloolefin content. Terpolymers are random; their molar masses, much higher than those in 1-octene terpolymers, are in a range useful for industrial applications. Finally, T_g values up to 152 °C were obtained. For similar N content, poly(E-ter-N-ter-C₈N)s and poly(E-ter-N-ter-DCPD)s have the lowest and the highest T_g values, respectively. Thus, the presence of an eight-carbon atom pendant chain in C₈N increases the flexibility of the polymer chain more than a five-carbon atom pendant chain in C₅N. The higher rigidity of C₅N may lead to lower activities and to increasing probability of σ-bond metathesis and chain termination, as evidenced by chain-end group analysis.