Copolymerization of ethylene and non-conjugated dienes with Cp₂ZrCl₂/MAO catalyst system

Ethylene was copolymerized with linear, non-conjugated dienes by the metallocene catalyst system Cp₂ZrCl₂/ MAO at 90⁰C. The dienes were 1,5-hexadiene (HD), 1,7-octadiene (OD) and 7-methyl-1,6-octadiene (MOD). Incorporation of the dienes was studied by ¹H and ¹³C-NMR and FTIR. According to the results, HD formed only five-member rings to polyethylene, even though selectivity towards cyclization has been reported to decrease when HD concentration in the reactor increases over 50mol%. OD and MOD were incorporated by 1,2-addition forming branches to the copolymer. The conversion of MOD remained under 4%, and was noticeably lower than that of HD and OD 025-40%). However, the effect of MOD on the physical properties of the copolymer was significant, whereas HD addition had almost no effect on the molar mass. The conversion of all dienes decreased when the diene concentration in the reactor was increased.