Crystalline polymers of dialkyl ketenes

In the polymerization of the ketenic compounds, either the opening of the ethylenic double bond or of the carbonyl double bond can occur. By using cationic catalysts, such as aluminum bromide, and catalysts which generally act with an anionic mechanism, constituted by metallorganic compounds, such as triethylaluminum dimethylketene polymers which appear crystalline by means of X‐ray examination have been prepared. Two types of crystalline polymers having different chemical structures have been isolated by fractionating extraction with suitable solvents. It has been observed that one type or the other prevails according to the type of catalysts employed. One of the crystalline polymers prepared by us, has a β‐ketonic structure, and it is produced by opening of the ethylenic double bond present in the monomer. The other crystalline polymer has the structure of the polyester type, and is formed by the alternate addition of one monomeric unit formed by the opening of the ethylenic bond and of another unit formed by the opening of the carbonyl bond. For both these polymers, the physical properties have been reported, and the degradation reactions which allows the determination of their chemical structures are described.