Theoretical Modeling of Ethene/Propene Copolymerization: a Quantum Mechanical/Stochastic Approach to the Microstructure of Block-Copolymers

One among the great challenges in polymer science is the deep understanding of the links between the catalyst features and its catalytic behavior toward monomers. Obviously, such goal has a great industrial and scientific interest for the design of copolymerization catalysts. In this respect, the fundamental role of steric hindrance of catalyst is widely accepted; conversely, the importance of the counter-ion, of the chain-control given by the ultimate or penultimate monomer and the competition between two different coordination sites still remain somewhat unclear1. In this work we describe theoretical study of the elementary steps involved in the copolymerization of ethene and propene by two C2-symmetric metallocene catalysts, rac-H2C-(Ind)2ZrCl2 and rac-H2C-(3-tBu-Ind)2ZrCl2 2. In thus, DFT analysis of reaction pathway gives us the energetics of insertions on the catalyst cation; a kinetic-Monte Carlo model instead, stochastically simulates the kinetic of copolymerization. The results obtained agree well with experimental distributions of triads and for the first time allow us to shed some light on the relative importance of the counter-ion, of the hypothetic penultimate effect and of the presence of two coordination sites.