Modeling of ethylene-norbornene copolymer microstructure in solution polymerization with homogeneous metallocene catalysts

The microstructure of ethylene-norbornene copolymer produced in solution polymerization is analyzed through kinetic modeling and experiments using homogeneous rac-Et(l-indenyl)(2)ZrCl2/methylaluminoxane catalyst in toluene at 70 degrees C. The sequence distribution function and average chain length equations are derived for terminal model and penultimate model. The model simulations show that both models provide similar predictions of average copolymer composition, especially at low norbornene concentration in the copolymer. However, at higher norbornene concentrations the penultimate model yields much better predictions of norbornene sequence length distribution than the terminal model. The terminal model has been inadequate in describing the copolymerization rate, whereas the penultimate model yields excellent predictions of rate behavior. The model calculations also indicate that at norbornene concentration in the copolymer larger than about 10 mol-%, the maximum ethylene block length is smaller than 70, prohibiting the formation of crystalline copolymer.