Along with the SPR studies, we cultivate fundamental investigations on the mechanisms of catalytic olefin polymerizations, aiming to identify the origin of the observed stereo-, regio- and chemo-selectivities for heterogeneous as well as molecular systems, and the dominant chain transfer pathways presiding over their polymer molecular weight capability. We typically do that by combining molecular kinetic observations with in-depth NMR polymer microstructure analyses. A recent example is the elucidation of the subtle effects governing tandem molecular catalysis under reversible trans-alkylation (“chain shuttling”) regime.

Purely computational tools can be exploited to model the elementary reaction steps of the polymerization process when the structure of the active species can be assumed to be known. At LSP we have carried out a solid benchmark of DFT protocols for modelling various reactions of interest in olefin polymerization, from simple olefin insertion to metal-carbon bond homolysis. Thanks to the so- optimized approach, accuracy needed not only for mechanistic understanding but also for reliable kinetic modelling has been achieved. This has been proven, for instance, by the successful modelling of comonomer affinities in ethene/α-olefin copolymerization.

More often, experimental and computational tools are combined in highly integrated studies. This is almost invariably the case for heterogeneous catalyst systems (e.g. of Ziegler-Natta type). Recent successful examples in molecular catalysis concern the correlations between structure and properties of octahedral bis(phenolate-ether) ‘post-metallocenes’,  as  well  as  the  identification of unprecedented pathways of chain transfer to solvent and to monomer.

Chain Transfer to Solvent in Propene Polymerization with Ti Cp-phosphinimide Catalysts: Evidence for Chain Termination via Ti–C Bond Homolysis. ACS Catal. 2016, 6, 7989-7993

Catalyst Mileage in Olefin Polymerization: The Peculiar Role of Toluene. Organometallics 2018, 37, 2872-2879

Toluene and α-Olefins as Radical Scavengers: Direct NMR Evidence for Homolytic Chain Transfer Mechanism

 Leading to Benzyl and “Dormant” Titanium Allyl Complexes. Organometallics 2018, 37 (22), 4189-4194

Formation and Activation of Zr/Hf Bis(phenolate-ether) Precatalysts Eur. J. Inorg. Chem. 2019, 3396-3410

Structure-Activity Relationships for Bis(phenolate-ether) Zr/Hf Propene Polymerization Catalysts. Eur. J. Inorg. Chem. 2020, 541-550

Furthermore, LSP has a long-standing tradition in investigating the complex cross reactivity of precatalysts and cocatalysts (activators). Recently, especially interesting results have been obtained on the structure and reactivity of methylaluminoxane (MAO) and some modifications thereof, by successfully integrating DFT modelling and advanced NMR spectroscopy (in collaboration with the research group of Prof. Alceo Macchioni at the University of Perugia).