It was reported that ethylene oxide was polymerized b y alkaline earth carbonates to give a very high-molecular polyether l ) . Propylene oxide has been known t o be polymerized by potassium hydroxide, propylene oxide-ferric salt ~o m p l e x~~~) or by trialkylaluminium with or without the use of c o~a t a l y s t s~~~) .We examined the ability of various organometallic compounds t o polymerize propylene oxide and found that diethylzinc has a remarkable catalytic activity when it is used in the presence of some active compounds. I n a previous paper 6), we reported that diethylzinc-alumina system induces the polymerization of propylene oxide to give a polymer having the intrinsic viscosity as high as 4.08.Further examinations have revealed that compounds such as oxygen, water and alcohol also exhibit similar effects on the propylene oxide polymerization. Since these compounds are known t o react with diethylzinc to decompose the latter rapidly, it is rather surprising that these active compounds show effective cocatalytic activities when they are used in appropriate amounts under suitable conditions. Recently, similar effect of water was reported by R. 0. cOLCLOUGH5) in the case of the polymerization of propylene oxide by trimethylaluminium, but nothing was mentioned on the effect of oxygen and alcohol.

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Diethylcadmium induces vinyl polymerization in the presence of some oxygen compounds. Copolymerization between styrene and methyl methacrylate using diethylcadmium resulted in the formation of copolymers having the same composition as those from the typical radical copolymerization. These results suggest a t least the propagation stage of the present polymerization to proceed according to the radical mechanism. However, benzoquinone or hydroquinone in an appropriate quantity was found to be an effective co-catalyst toward this polymerization. A possible mechanism for this is advanced. Comparative study of polymerizations with ethyl derivatives of zinc, aluminium and antimony has revealed that these polymerizations are also radical type in character Finally, in connection with the ZIEGLER-catalyst, the behavior of the mixture of diethylcadmium and titanium tetrachloride (4 : 1 in mole ratio) toward various vinyl monomers is examined. ZUSAMMENFASSUNG:Diathylcadmium lost in Gegenwart einiger Sauerstoffverbindungen die Vinylpolymerisation aus. Die Copolymerisation von Styrol und Methacrylsiiuremethylester mit Diathylcadmium liefert Copolymere mit den gleichen Einbauverhaltnissen wie im Fall einer typischen Radikalkettencopolymerisation. Dieses Ergebnis bedeutet, dal3 die Wachstumsreaktion der hier beschriebenen Polymerisation nach einem Radikalmechanismus verlauft.Benzochinon und Hydrochinon haben, wenn sie in geeigneten Mengen verwendet werden, eine beschleunigende Wirkung auf die Polymerisation. Ein moglicher Mechanismus fiir die Wirkung des Chinons und Hydrochinons wird aufgezeigt. Vergleichende Polymerisationsversuche mit den dthylderivaten des Zink, Aluminium und Antimon zeigen, daD auch sie nach einem Radikalmechanismus verlaufen.SchlieDlich wird, in Analogie zum ZIEGLER-Katalysator, das Verhalten eines Gemisches von Diathylcadmium und Titantetrachlorid im Molverhiiltnis 4 : 1 an verschiedenen Vinylmonomeren untersucht.

High-resolution nmr studies have been carried out on the organolithium polymerization of butadiene in hydrocarbon solvents. As a measure of any possible complexation between the monomer and the active chain end, the proton resonance spectrum of butadiene was determined in the presence and absence of shortchain poly(perdeuteriobutadienyl)lithum (xn ~20) at high concentrations (0.2 M) of both, in benzene-d6 or toluene-ds-No effect was observed on the proton resonances of the monomer, indicating that, if such complexation does occur, the concentration of the complex must be very low (<1% based on a slow exchange rate). Using ethvllithium-da to initiate short-chain poly(butadienyl)lithium and the technique of "pseudotermination" by butadienede, it has been found possible to assign the three resonance peaks corresponding with protons on the terminal carbon («), as well as the penultimate [ß] and antepenultimate ( ) carbon atoms in the chain. These peaks indicate that the terminal chain unit has a 1,4 structure (no detectable 1,2), whereas the in-chain units show about 9% 1.2 structure. This has been taken to indicate the existence of an equilibrium between a localized (covalent) and a delocalized ( -allyl) chain-end unit, the latter being in too low a concentration to be detected, but leading to the inclusion of a 1,2 in-chain unit by subsequent monomer addition.