Alternating copolymerization of propylene oxide and carbon dioxide with an alumina supported diethylzinc catalyst

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Abstract
Diethylzinc was allowed to react with γ‐alumina in n‐heptane at 50°C, and the copolymerization of propylene oxide and carbon dioxide was investigated in some detail at 30–90°C by using the reaction product as a catalyst. From an analysis of the catalyst it was found that diethylzinc reacted with the surface hydroxyl groups of γ‐alumina mainly to give the following A‐type species by evolving ethane: magnified image The catalyst showed considerably high activity for the copolymerization. The polymer obtained was a white solid with a high molecular weight soluble in benzene, acetone, dioxane, and methylene chloride and insoluble in diethyl ether and water. It was confirmed as an alternate copolymer of propylene oxide and carbon dioxide.The copolymerization was also conducted with a reaction mixture of the catalyst and catechol in which the molar ratio of catechol to the A‐type species was varied. The copolymerization activity decreased linearly with an increase in the molar ratio and disappeared completely at the molar ratio of unity.On the basis of these results it has been concluded that the A‐type is the true active species for the copolymerization.