1994 Volume 51 Issue 10 Pages 647-651
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 formulae are applied to the polypropylenes polymerized by Ziegler-Natta catalysts with external alkoxysilane donors. For both of unfractionated samples and heptane-insoluble fractions, the followings were clarified: 1) the transformation from symmtric to (fluctuating) asymmetric centers the transformation of one (hereafter, L) site is much enhanced than that of Dsite, 2) the monotonous increase of isotacticity as a result of the increase of the concentration of the donors is due to the increase ofPLL, 3) aromatic donors are effective than aliphatic ones for the improvement of isotacticity, and 4) the improvement of isotacticity after an addition of the alkoxysilanes is not due to the contribution from both of L and D sites, but the positive contribution from the former is larger than the negative one from the latter.
