The a-diolefins of the general formula CH-CH (CH&L! H= CH, where n is equal to 4, 5, 6, 7, 8, 9, 10, 11, 12, 14 and 18, have been prepared and polymerized with the system aluminum triisobutyl-titanium tetrachloride. The polymers obtained consist of both soluble and insoluble, cross-linked fractions. The results of quantitative infrared and bromination determinations indicate that the soluble polymers possess cyclic units, open chain units ...