Oscillating Sterocontrol: A Strategy for the Synthesis of Thermoplastic Elastomeric Polypropylene
Abstract
A strategy has been developed for the synthesis of thermoplastic elastomeric polypropylene based on the catalytic activity of the unbridged metallocene bis(2-phenylindenyl)zirconium dichloride [(2-Phlnd)_2ZrCl_2]. This catalyst was designed to isomerize between achiral and chiral coordination geometries during the polymerization reaction to produce atactic-isotactic stereoblock polymers. The metallocene precursor (2-Phlnd)_2ZrCl_2 in the presence of methylaluminoxane polymerizes propylene to yield rubbery polypropylene. The isotacticity of the polymer, described by the isotactic pentad content, increases with increasing propylene pressure and decreasing polymerization temperature to produce polypropylenes with an isotactic pentad content ranging from 6.3 to 28.1 percent.
- Publication:
-
Science
- Pub Date:
- January 1995
- DOI:
- 10.1126/science.267.5195.217
- Bibcode:
- 1995Sci...267..217C