a product of butadiene polymerization. Molecules of butadiene may join together in the chain at the positions cis-1,4 (I); trans-1,4 (II); and 1,2- (III):

The relationship and distribution of the structures in the chain, which depend on the type of catalyst and on the method and conditions of polymerization, determine the properties of the polymer.

Four stereoregular polybutadienes (cis-1,4; trans-1,4; isotactic-1,2; syndiotactic-1,2), which are produced by stereo-specific polymerization, and several statistical polybutadienes are known. Rubber-like polybutadienes are of great industrial value. Polybutadienes that contain more than 70–90 percent trans-1,4 or 1,2- links of isotactic or syndiotactic structure are white, linearly crystallizing fiber-forming plastics. In the USA, trans-1,4 polybutadiene is produced commercially under the trade name Trans-4; it contains about 90 percent trans-1,4 links (number-average molecular weight, 100,000). It is soluble in benzene and CCl₄ and is vulcanized by sulfur. Trans-4 vulcanizates are characterized by high strength and hardness and by a durability surpassing that of vulcanizates of natural and butadiene-styrene rubbers. Trans-4 is used in the manufacture of sole rubbers, flooring, gaskets, and other commercial products.