High‐Throughput Screening in Olefin‐Polymerization Catalysis: From Serendipitous Discovery Towards Rational Understanding

Abstract

High-throughput-screening (HTS) tools and methods are used more and more, especially in industry, in the search for new, selective organometallic catalysts. In most cases, the approach is, in essence, empirical, and the strategy is to increase the number of experiments that can be run at a given place in a given time. Highly miniaturized, parallel reaction setups have been implemented for the rapid assessment of whether novel catalysts resulting from the structural amplification of a basic framework are "good" or "bad" with respect to the properties of interest, and, depending on the response, worthy of a subsequent, more-careful evaluation. In this article, we demonstrate that it is possible to utilize these state-of-the-art HTS platforms with a different strategy: the rapid generation of reliable kinetic data for mechanistic studies in view of a thorough understanding and rational catalyst design. Ziegler-Natta-type catalytic olefin polymerization will be used throughout as an example.

Ethylene polymerization over supported titanium‐magnesium catalysts: Effect of polymerization parameters on the molecular weight distribution of polyethylene

“…These catalysts contain several types of active sites differing in their reactivity and these sites produce polymer molecules with different average molecular weights. It is well known that multiple‐site titanium‐magnesium catalysts (TMC) produce PE with broad MWD ( M w /M n = 3‐81–8). The polydispersity value and distribution of active sites are dependent upon the catalyst composition, conditions of its preparation, modifying agents being introduced into the catalyst, and polymerization conditions.…”

An Integrated High Throughput Experimentation/Predictive QSAR Modeling Approach to ansa-Zirconocene Catalysts for Isotactic Polypropylene

“…Notably, with several catalysts in the set the generation of stereodefects and/or chain termini turned out to fall under the definition of ‘rare events’ (<0.1% of TOF). Measuring said microstructural features with high accuracy in HTE mode represented an extreme but also mandatory technical challenge [ 19 , 20 , 21 ], because i-PP properties depend crucially on them, and even minute differences in their fractional abundance have a strong impact on the polymer application window [ 87 , 88 , 89 , 90 ]. We managed to overcome the problem with the only exception of catalysts approaching ‘perfect’ stereoselectivity (>0.9998%), ranking such catalysts was not possible since the fraction of stereodefects in the polymers turned out to be lower than our 13 C NMR evaluation uncertainty (±0.02 mol%).…”

“…The cells, with a working volume of 5.0 mL, feature an 800 rpm magnetically coupled stirring, and individual online reading/control of temperature, pressure, monomer uptake, and uptake rate. The setup and the operating protocol, described in full detail in References [ 19 , 20 ], are reported in the SI and have been used successfully before in various homogeneous and heterogeneous polymerization studies [ 13 , 21 , 24 ]. Polymerization conditions were as follows (and identical to those used in Reference [ 13 ]): T = 60 °C; p (C 3 H 6 ) = 4.5 or 6.6 bar; activator and scavenger Al( iso -butyl) 3 (TIBA)/N,N-dimethylanilinium tetrakis(perfluorophenyl)borate (AB) or MAO.…”

“…As a matter of fact, the initial identification of catalyst hits/leads was followed by structure optimization with conventional methods. More recently, in our labs we found ways to improve the precision and accuracy of the approach, by implementing highly controlled polymerization protocols on a state-of-the-art HTE reaction platform (Freeslate—former Symyx—Parallel Polymerization Reactor (PPR)), and integrating said platform with fast and thorough polymer characterization techniques, including Rapid-GPC, high-temperature cryoprobe 13 C NMR, Differential Scanning Calorimetry (DSC), and analytical Crystallization Elution Fractionation (aCEF) [ 19 , 20 , 21 , 22 , 23 , 24 ]. This workflow is now exploited to rapidly generate large catalyst structure-properties databases for optimization using predictive QSAR modeling [ 13 ].…”

Enabling technologies in polymer synthesis: accessing a new design space for advanced polymer materials

“…If it is not possible to use an air-tolerant chemistry, a wide range of studies have made use of glovebox-contained synthesisers purged with inert gas to successfully achieve polymerisation using standard formulations. 130,131 High-throughput synthesisers have also been used for both and synthesis 132 and screening 133 of Ziegler-Natta catalysts used for (particularly industrially relevant) olefin polymerisations and the synthesis of appropriate support materials. 134 Adapting such platforms to perform at high pressure is required where the polymerisation itself is monitored.…”