Continuous solution polymerization of ethylene/dicyclopentadiene and its reaction kinetics

To synthesize cycloolefin copolymers （COC） from readily available and economical monomers, the continuous solution copolymerization of ethylene and dicyclopentadiene （DCPD） was investigated using the rac-Et（Ind）₂ZrCl₂ / Ph₃CB（C₆F₅）₄ / ⁱBu₃Al catalyst system. The effects of key parameters including reaction temperature, ethylene pressure, and DCPD mass fraction were systematically examined. Under steady-state conditions, the monomer reactivity ratios were determined, enabling the establishment of a copolymer composition model and an apparent copolymerization rate equation. The results demonstrated that in this catalytic system, the reactivity ratio of ethylene （r_E） exceeds 1 and increases with temperature, whereas that of DCPD （r_D） remains below 1 but exhibits a similar temperature-dependent rise. The product r_E r_D < 1 confirmed the formation of a random copolymer. Polymerization activity displayed a non-monotonic dependence on temperature, initially increasing before declining, while copolymer molecular weight decreases steadily. DCPD incorporation increased with its feed mass fraction. Kinetic analysis indicated that DCPD enhanced copolymerization, as supported by the calculated activation energies for homo- and copolymerization. The copolymer composition follows the first-order Markov model, and the apparent kinetic equation is derived as R_p = 0.0156M_DM_E^0.26 when the catalyst molarity sets at 1 μmol·mL⁻¹. The research conclusion provides a reference for the industrial production of DCPD based COC.