A Systematic Study of the Temperature-Induced Performance Decline of <i>ansa</i>-Metallocenes for iPP

Highly accurate high-throughput experimentation
(HTE) data for
a set of 21 silicon-bridged C2-symmetric ansa-zirconocenes in propene homopolymerization were collected
and were used to develop quantitative structure – activity
relationship (QSAR) models for several performance indicators at high
polymerization temperature (Tp = 100 °C)
by using chemically meaningful descriptors. Most notably, stereoselectivity
is well described by a two-descriptor model linking the quadrant model
for stereoselectivity (sterics) with the chain epimerization model
(electronics). The catalysts show widely varying temperature responses,
most notably on stereoselectivity and molar mass capability, while
the regioselectivity response is uniformly weak. Soft conformational
locks lose their performance rapidly while hard conformational locks
offer enhanced performance even at high temperatures. The quest for
high-temperature stable, well-performing ansa-zirconocenes
will unquestionably lead to systems with enhanced rigidity.