ASYMMETRIC MARKOVIAN PROCESS IN THE POLYP ROPYLENE OBTAINED BY ZIEGLER-NATTA CATALYST WITH EXTERNAL ALKOXYSILANE DONORS

The formulae for conditional probabilities are derived with the terms of NMR triad tacticities for the polymers whose polymerization process is described by the asymmetric Markovian process. The obtained formul ae are applied to the polypropylenes polymerized by Ziegler-Natta cata lysts with external alkoxysilane donors. For both of unfractionated sa mples and heptane-insoluble fractions, the followings were clarified: 1) on the transformation from symmtric to (fluctuating) asymmetric cen ters the transformation of one (hereafter, L) site is much enhanced th an that of D site, 2) the monotonous increase of isotacticity as a res ult of the increase of the concentration of the donors is due to the i ncrease of p(LL), 3) aromatic donors are effective than aliphatic ones for the improvement of isotacticity, and 4) the improvement of isotac ticity after an addition of the alkoxysilanes is not due to the contri bution from both of L and D sites, but the positive contribution from the former is larger than the negative one from the latter.