An investigation of the effect of chain length on stereo-regulation with C2 symmetric metallocene catalysts
Date
2006-12
Authors
Amer, Ismael
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
This study concerns the polymerization of propylene both in the presence and absence of
molecular hydrogen. The percentage of hydrogen used as a terminating agent in the
polymerization reactions was varied from 0.1 wt% to 15.0 wt% in order to compare a
variety of polymers with different percentages of hydrogen incorporated. Two ansa
metallocene catalysts were used: (A) rac-[ethylene bis(indenyl)] zirconium dichloride
(rac-Et(Ind)2ZrCl2) and (B) dimethylsilyl-bis(2-methyl benzoindenyl) zirconium
dichloride (rac-Me2Si(2-MeBenz[e]Ind)2ZrCl2). Methylaluminoxane (MAO) was used as
cocatalyst for both of the two catalysts.
Characterization of the polymers included using nuclear magnetic resonance
spectroscopy (NMR) for information concerning the microstructure of the polymers, high
temperature gel permeation chromatography (HT-GPC) for molecular weight and
molecular weight distributions and differential scanning calorimetry (DSC) to investigate
the melting point and crystallization behaviour of the polymers.
The polypropylenes prepared with the dimethylsilyl-bis(2-methyl benzoindenyl)
zirconium dichloride catalyst system were compared to the polypropylenes synthesized
with ethylene-bis(indenyl) zirconium dichloride. In particular, the effects of hydrogen on
the microstructure, molecular weight, molecular weight distribution, melting point and
crystallization behaviour were investigated.
Description
Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006.
Keywords
Dissertations -- Polymer science, Theses -- Polymer science, Metallocene catalysts