The infrared analysis of ethylene-propylene copolymers allowed us to confirm that, in the syndiospecific polymerization of propylene, insertion occurs on metal-secondary carbon bonds. The monomer orientation in the insertion is essentially due to steric effects.
The homopolymerization of dicyclopentadiene induced by catalysts, containing transition metals of the groups IV, V, VI, and VIII of the periodic table of elements, yields polymers having different monomeric units depending on the transition metal and on the acid/base character of the catalytic system. Seven different monomeric units, some of which not observed up to now, could be assigned on the basis of infrared.spectroscopic measurements. All monomeric units derive from the ring cleavage or from the addition to the double bonds of both unsaturated five-membered rings, whereas the saturated fivemembered ring of the monomer is always retained in the polymer. I n the presence of some particular catalysts the polymerization leads to products having uniform chemical structure.
ZUSAMMENFASSUNG:Die Homopolymerisation von Dicyclopentadien unter Einwirkung von Katalysatoren, die Nebengruppenelemente der IV., V., VI. und VIII. Gruppe des Periodensystems enthalten, liefert Polymere mit verschiedenartigen Monomereinheiten je nach dem Nebengruppenelement und dem Saure/Base-Charakter des Katalysatorsystems. Sieben verschiedene Monomereinheiten, von denen einige bisher noch nicht bekannt waren, konnten auf Grund der Infrarot-Analyse zugeordnet werden. Alle Monomereinheiten entstehen durch Ringspaltung oder durch Addition an die Doppelbindungen der beiden ungesattigten fiinfgliedrigen Ringe, wahrend der gesattigte funfgliedrige Ring des Monomeren stets in den Polymeren wiedergefunden wird. I n Gegenwart einiger bestimmter Katalysatoren liefert die Polymerisation Produkte mit chemisch einheitlicher Struktur.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.