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Variation in the Isospecific Active Sites of Internal Donor‐Free MgCl 2 ‐Supported Ziegler Catalysts: Effect of External Electron Donors
Author(s) -
Matsuoka Hitoshi,
Liu Boping,
Nakatani Hisayuki,
Terano Minoru
Publication year - 2001
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/1521-3927(20010301)22:5<326::aid-marc326>3.0.co;2-g
Subject(s) - tacticity , active site , catalysis , electron donor , steric effects , ziegler–natta catalyst , polymerization , chemistry , polymer chemistry , materials science , organic chemistry , polymer , ethylene
The stopped‐flow polymerization of propylene was carried out using an internal donor‐free MgCl 2 ‐supported Ziegler catalyst in the absence or presence of external electron donors. The variation in the isospecific active sites was investigated based on the isotacticity distribution of the poly(propylene) analyzed by the TREF method. Highly isospecific active sites derived from the highest isotactic fraction (elution temperature by TREF: >112 °C) exist in the electron donor‐free catalyst system. The addition of external electron donors converted parts of the aspecific into isospecific active sites, but showed no effects on the highest isospecific active sites. The external electron donor sterically affects a coordination vacancy of each aspecific titanium species and, consequently, transfers it into an isospecific active site of high, but not highest isospecificity.