The stereochemistry of polypropenes obtained in the presence of several MgCl2-supported Ziegler-Natta catalyst systems comprising different Lewis bases has been investigated by C-13 NMR spectroscopy, with special attention paid to the ''less tactic'' (heptane-soluble) fractions. These have been found to consist of ''tendentially isotactic'' and ''tendentially syndiotactic'' stereosequences, in largely variable amounts (depending on the catalyst system). The microstructure of the former is in accordance with the enantiomorphic site model, whereas that of the latter suggests a stereocontrol arising from the asymmetry of the growing chain end. In both cases, propene insertion is primary (1-2). Polymerization conditions leading to the formation of ''syndiotacticrich'' polymers showing syndiotactic crystallinity have been identified.
PROPENE POLYMERIZATION IN THE PRESENCE OF MGCL2-SUPPORTED ZIEGLER-NATTA CATALYSTS .4. EFFECTS OF LEWIS-BASES ON POLYMER STEREOCHEMISTRY / Busico, Vincenzo; Corradini, P; Demartino, L; Graziano, F.; Iadicicco, A.. - In: DIE MAKROMOLEKULARE CHEMIE. - ISSN 0025-116X. - STAMPA. - (1991), pp. 49-57.
PROPENE POLYMERIZATION IN THE PRESENCE OF MGCL2-SUPPORTED ZIEGLER-NATTA CATALYSTS .4. EFFECTS OF LEWIS-BASES ON POLYMER STEREOCHEMISTRY
BUSICO, VINCENZO;
1991
Abstract
The stereochemistry of polypropenes obtained in the presence of several MgCl2-supported Ziegler-Natta catalyst systems comprising different Lewis bases has been investigated by C-13 NMR spectroscopy, with special attention paid to the ''less tactic'' (heptane-soluble) fractions. These have been found to consist of ''tendentially isotactic'' and ''tendentially syndiotactic'' stereosequences, in largely variable amounts (depending on the catalyst system). The microstructure of the former is in accordance with the enantiomorphic site model, whereas that of the latter suggests a stereocontrol arising from the asymmetry of the growing chain end. In both cases, propene insertion is primary (1-2). Polymerization conditions leading to the formation of ''syndiotacticrich'' polymers showing syndiotactic crystallinity have been identified.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.