Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta catalyst, high molecular weight and stereochemically controlled linear polymers can be synthesized at a large scale. For example, high molecular weight and ultrahigh molecular weight polyethylene, used for making underground pipes and bulletproof vests, are synthesized using the Ziegler–Natta catalyst. This catalyst also facilitates the synthesis of polymers of specific tacticity. For instance, isotacticpolypropylene, with chiral centers on the same side, can be synthesized using a specific Ziegler–Natta catalyst.