The polyethylene obtained in the presence of the catalyst constituted by the meso isomer of the prototypical zirconocene complex (ethylene)bis(1-indenyl)zirconium dichloride activated by methylalumoxane is characterized by the presence of ethyl branches. The intensities of the 13C NMR signals associated with these branches indicate that there are about 1-2 ethyl groups per 100 monomer units. As a consequence, the melting temperature is 10-15 °C lower than the linear polyethylene obtained with the rac mixture of the same zirconocene complex. On the basis of kinetic evidence, a branching mechanism that involves a beta-H transfer to the coordinated ethylene is proposed.
Branched Polyethylene by Ethylene Homopolymerization with meso-Zirconocene Catalyst
IZZO, Lorella;CAPORASO, Lucia;OLIVA, Leone
1999-01-01
Abstract
The polyethylene obtained in the presence of the catalyst constituted by the meso isomer of the prototypical zirconocene complex (ethylene)bis(1-indenyl)zirconium dichloride activated by methylalumoxane is characterized by the presence of ethyl branches. The intensities of the 13C NMR signals associated with these branches indicate that there are about 1-2 ethyl groups per 100 monomer units. As a consequence, the melting temperature is 10-15 °C lower than the linear polyethylene obtained with the rac mixture of the same zirconocene complex. On the basis of kinetic evidence, a branching mechanism that involves a beta-H transfer to the coordinated ethylene is proposed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
