Polymerization of organized monomers

Abstract

The current explanations of olefin and vinyl monomer polymerization propose that monomer molecules are successively added one by one to the growing polymer chain. This may be true if the monomer molecules exist as individual species in a polymerizing system, e.g. in dilute solutions of monomer. There are cases, however, in which monomer molecules are organized: bulk liquid monomer, solid monomer, a monomer monolayer adsorbed on a support, etc. Various supra-molecular species and particles of monomer exist in such cases. In the 1960-ties, Semenov, Kargin and Kabanov proposed a theory of organized monomer polymerization. In the last 25 years, our research group has further developed and applied that theory to various polymerizing systems: the radical polymerization of compressed ethene gas, the radical polymerization of liquid methyl methacrylate, olefin polymerization by transition metals and by Al-based catalysts. An outline of the main achievements are presented in this article

The charge percolation mechanism and simulation of Ziegler-Natta polymerizations, Part VII: Effects of the distribution of chromium active centers on silica on the polymerization of ethylene

“…Hence, the CPM and the Kobozev theory predict that the values of P Cr and P S should decrease at the very low concentrations of chromium. This effect has been investigated by computer simulation 8,13,15 (Fig. 6, top) and predicted by a very simple calculation.…”

“…Consequently, oligomers with a low degree of polymerization (X n ) will be obtained initially, but X n should increase with increasing polymerization time. 8,13 Simultaneously, the number of active centers (A and D) remaining on the support should decrease. Experimental data 14 confirmed such predictions of the CPM (Fig.…”

“…13 Two dimensional percolation processes were simulated. (The computer simulation of ZN polymerization by the CPM is explained elsewhere.…”

“…6, top) and predicted by a very simple calculation. 13 A sharp maximum of metal productivity (P Mt,max ) is obtained 15 if the number of active centers is 3 or 5 per surface region in the SAM sequences of one-and two-dimensional percolation processes, respectively, and if the number of Mt(IV) is equal to that of Mt(II). The value of P Mt,max depends on the size of region, i.e., the number of adsorption sites in it -the more sites, the higher is P Mt,max .…”

“…21 The same effect was noticed in other Z-N polymerization systems. 8,13,15 Several dozens of experiments have been analyzed and explained by the Kobozev theory and by the CPM. Some examples were presented: the ethylene polymerization by CrO x /SiO 2 , 8 propylene polymerization by TiCl 4 /AlEt 3 /MgCl 2 , by TiCl 4 /AlEt 2 Cl/graphite and by metallocene/MAO systems.…”