A Systematic Study of the Temperature-Induced Performance Decline of ansa-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.