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

Ethylene was copolymerized with linear, non-conjugated dienes by the metall ocene catalyst system Cp2ZrCl2/MAO at 90 degrees C. The dienes were 1,5-hex adiene (HD), 1,7-octadiene (OD) and 7-methyl-1,6-octadiene (MOD). Incorpora tion of the dienes was studied by H-1 and C-13-NMR and FTIR. According to t he results, HD formed only five-member rings to polyethylene, even though s electivity towards cyclization has been reported to decrease when HD concen tration in the reactor increases over 50 mol%. OD and MOD were incorporated by 1,2-addition forming branches to the copolymer. The conversion of MOD r emained under 4%, and was noticeably lower than that of HD and OD (25-40%). 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. T he conversion of all dienes decreased when the diene concentration in the r eactor was increased. (C) 1999 Elsevier Science Ltd. All rights reserved.