Coordination addition polymerization

Many polymers are now manufactured on a, commercial scale using Ziegler-Natta catalysts. Indeed, stereoregular (isotactic) polypropylene of high molecular weight, which cannot be made by free-radical or ionic polymerization, has already achieved the status of a commodity plastic. The scientific and practical significance of Ziegler and Natta s work earned them the joint award of the Nobel Prize in Chemistry in 1963. 

Since the Ziegler-Natta catalyst systems appear to function via formation of a coordination complex between the catalyst, growing chain, and incoming monomer, the process is also referred to as coordination addition polymerization and the catalysts as coordination catalysts. Other types of complex catalysts that have 

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Polypropylene (PP) is a semicrystalline commodity thermoplastic produced by coordination addition polymerization of propylene monomer [197]. Most frequently, stereospecific Ziegler-Natta catalysts are used in industrial processes to produce highly stereospecific crystalline isotactic (iPP) and syndiotactic (sPP) polymer with a small portion of amorphous atactic PP as a side product. Polymerization of non-symmetrical propylene monomer yields three possible sequences however, the steric effect related to the methyl side group highly favors the head-to-tail sequence. The occurence of head-to-head and tail-to-tail sequences produces defects along the PP chain [198]. Presence of such defects affects the overall degree of crystallinity of PP. 

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