ASYMMETRIC MARKOVIAN ANALYSIS OF THE POLYMERIZATION MECHANISM OF PROPENE BY ZIEGLER-NATTA CATALYSIS AND EXTERNAL ALKOXYSILANE DONORS

The formulae for conditional Probabilities are derived with the term of NMR triad tacticities for the polymers whose polymerization process is described by an asymmetric Markovian process. The formulae obtained are applied to the polypropylene polymerized by Ziepler-Natta catalysis with external alkoxysilane donors. For both, unfractionated samples and heptane-insoluble fractions, four evidences are clarified as follows: 1) on the transformation from symmetric to (fluctuating) asymmetric sites the transformation of one (hereafter, L) site is such more enhanced than that of the other (D) site, 2) monotonous increase of isotacticity with an increase of the concentration of the donor is due to the increase of P-LL, 3) aromatic donors are more effective than aliphatic ones for the improvement of isotacticity, and 4) the improvement of isotacticity after an addition of alkoxy-silane is not due to the contribution from both of L and D sites, but the competition between the larger positive contribution from the former and the smaller negative one from the latter.