Polymer Structure Prediction by Computer Simulation of Ziegler-Natta Polymerization based on Charge Percolation Mechanism

摘要

Recently, a new charge percolation mechanism (CPM) of the Ziegler-Natta (ZN) polymerization of olefins by supported transition metal (Mt) complexes has been presented: a macromolecular chain is formed by polymerization of the monomer cluster (nM) adsorbed on the support (S) between two immobilized Mt ions, some in the higher (Mt~(n+1), i.e. acceptors) and the other in the lower (Mt~(n-1), i.e. donors) oxidation state: (Mt~(n-1)···nM···Mt~(n+1))/S → (Mt~n Mt~n)/S + polymer. A special computer program «Lattice» has been developed to simulate olefin polymerization based on CPM using a Monte Carlo procedure. The effects of reaction conditions (Mt concentration, Mt/S ratio, sequence of chemical components addition and time) of ethylene and propylene polymerization by various Mt precursors (TiCl_4/MgCl_2, CrO_x) and supports (MgCl_2, SiO_2) on molecular mass and molecular mass distribution can be predicted by simulation and confirmed by published experimental results.