Copolymerization of ethylene/diene with different metallocene catalysts

Copolymerizations of ethylene and 1,7-octadiene were carried out employing homogeneous catalysts Cp2ZrCl2, Ph2C(Flu,Cp)ZrCl2 and Et(Ind)(2)ZrCl2, and methylaluminoxane as cocatalyst. The polymerization characteristics, such as catalytic activity, polymerization rate, copolymer composition, and thermal properties were examined in relation to the catalyst type. Different comonomer concentrations were employed, and the reaction time was varied, ranging from 1 h up to 4 h, at 90 degrees C and at 0.5 bar ethylene pressure. The results showed that the catalyst Cp2ZrCl2 was more efficient than Et(Ind)(2)ZrCl2 in the preparation of high diene content ethylene/1,7-octadiene copolymers. On the other hand, Et(Ind)(2)ZrCl2 and Ph2C(Flu,Cp)(2)ZrCl2 catalysts produced low insaturation content but possibly formed cyclic structures and crosslinking.