Short and long chain branching of polyethene prepared by means of ethene copolymerization with 1-eicosene using MAO activated Me2Si(Me4Cp)((NBu)-Bu-t)TiCl2

Ethene copolymers with 1-eicosene were prepared using the methylaluminoxane (MAO) activated dimethylsilanediyl (tetracyclopentadienyl)(tert-butylamido )-titanium dichloride (Me2Si(Me4Cp)((NBu)-Bu-t)TiCl2, CBT) catalyst system in slurry polymerization. The thermal behavior of the polymers was studied by differential scanning calorimetric (DSC) measurements in order to invest igate the influence of long alkyl-branches on polyethene crystallinity. Upo n increasing the incorporation of 1-eicosene from 0 to 50 wt.-%, the meltin g temperature decreased from 135 degrees C to 35 degrees C. The presence of a second peak in the DSC curves of ethene/1-eicosene copolymers with an in corporation of 1-eicosene exceeding 39 wt.-% was attributed to side chain c rystallization. CBT is well known for introducing long chain branches (LCB) into polyethene. Accordingly, the presence of additional long chain branch es (with a chain length of more than 100 carbon atoms) was detected using r heological measurements. In oscillatory and creep tests, samples with low i ncorporation of 1-eicosene showed a behavior typical of long chain branched polymers. Poly(ethene-co-1-eicosene)s with high incorporation of 1-eicosen e behaved like linear polymers, whereas ethene homopolymers contained less LCB. A long chain branching index (BI) was defined using terminal relaxatio n times. A correlation between BI and 1-eicosene content in the feed, as we ll as the number of long chain branches was established.