Coordination polymerization is a form of addition polymerization

Addition polymerization

Chain growth polymerization is a polymerization technique where unsaturated monomer molecules add on to a growing polymer chain one at a time...

 in which monomer

Monomer

A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...

 adds to a growing macromolecule

Macromolecule

A macromolecule is a very large molecule commonly created by some form of polymerization. In biochemistry, the term is applied to the four conventional biopolymers , as well as non-polymeric molecules with large molecular mass such as macrocycles...

 through an organometallic active center . The development of this polymerization

Polymerization

In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...

 technique started in the 1950s with heterogeneous Ziegler-Natta catalyst

Ziegler-Natta catalyst

A Ziegler–Natta catalyst is a catalyst used in the synthesis of polymers of 1-alkenes . Three types of Ziegler–Natta catalysts are currently employed:* Solid and supported catalysts based on titanium compounds...

s based on titanium tetrachloride

Titanium tetrachloride

Titanium tetrachloride is the inorganic compound with the formula TiCl4. It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. TiCl4 is an unusual example of a metal halide that is highly volatile...

 and an aluminium

Aluminium

Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 co-catalyst such as methylaluminoxane

Methylaluminoxane

Methylaluminoxane, commonly called MAO, is a white solid with the general formula n.-Physical properties:MAO is pyrophoric, and is violently reactive with any chemical bearing an acidic proton. However, MAO is generally used as a solution in an hydrocarbon due to its relatively high solubility in...

.
Coordination polymerization has a great impact on the physical properties of vinyl polymer

Vinyl polymer

Vinyl polymers are a group of polymers derived from vinyl monomers. Their backbone is an extended alkane chain, made by polymerizing an alkene group into a chain . In popular usage, "vinyl" refers only to polyvinyl chloride...

s such as polyethylene

Polyethylene

Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...

 and polypropylene

Polypropylene

Polypropylene , also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes...

 compared to the same polymers prepared by other techniques such as free radical polymerization. The polymers tend to be linear and not branched and have much higher molar mass

Molar mass

Molar mass, symbol M, is a physical property of a given substance , namely its mass per amount of substance. The base SI unit for mass is the kilogram and that for amount of substance is the mole. Thus, the derived unit for molar mass is kg/mol...

. Coordination type polymers are also stereoregular and can be isotactic or syndiotactic instead of just atactic. This tacticity

Tacticity

Tacticity is the relative stereochemistry of adjacent chiral centers within a macromolecule. The practical significance of tacticity rests on the effects of tacticity on the physical properties of the polymer...

 introduces crystallinity

Crystallinity

Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion. In a gas, the relative positions of the atoms or...

 in otherwise amorphous polymers. From these differences in polymerization type the distinction originates between low-density polyethylene (LDPE), high-density polyethylene (HDPE) or even ultra-high-molecular-weight polyethylene (UHMWPE).

Polymerizations catalysed by metallocenes occur via the Cossee-Arlman mechanism

Cossee-Arlman mechanism

The Cossee-Arlman mechanism in polymer chemistry is the main pathway for the formation of C-C bonds in the polymerization of alkenes. The mechanism features an intermediate coordination complex that contains both the growing polymer chain and the monomer...

. The active site is usually anionic but cationic coordination polymerization also exists.

In many applications Ziegler-Natta polymerization is succeeded by metallocene catalysis polymerization. This method is based on homogeneous metallocene

Metallocene

A metallocene is a compound typically consisting of two cyclopentadienyl anions bound to a metal center in the oxidation state II, with the resulting general formula 2M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride, vanadocene dichloride...

 catalysts such as the Kaminsky catalyst

Kaminsky catalyst

A Kaminsky catalyst is a catalytic system for alkene polymerization discovered in 1980. Kaminsky catalysts are based on metallocenes of group 4 transition metals with methylaluminoxane . These catalysts are a type of Ziegler-Natta catalyst, but they are homogeneous and show extremely high activity...

 discovered in the 1970s. The 1990s brought forward a new range of post-metallocene catalyst

Post-metallocene catalyst

A post-metallocene catalyst is a kind of catalyst for olefin polymerization. "Post-metallocene" refers to the generation of catalysts following Kaminsky catalysts, which are metallocene catalysts discovered in 1980 by Walter Kaminsky, and have been highly publicized in the olefin polymerization...

s.

Typical monomers are nonpolar ethylene

Ethylene

Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...

 and propylene

Propylene

Propene, also known as propylene or methylethylene, is an unsaturated organic compound having the chemical formula C3H6. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons, and it is also second in natural abundance.-Properties:At room temperature and...

. The development of coordination polymerization that enables copolymerization with polar monomers is more recent Examples of monomers that can be incorporated are methyl vinyl ketones methyl acrylate

Methyl acrylate

Methyl acrylate is a volatile chemical compound classified as a methyl ester. It has a characteristic acrid odor used in the preparation of polyamidoamine dendrimers typically by Michael addition with a primary amine....

  and acrylonitrile

Acrylonitrile

Acrylonitrile is the chemical compound with the formula C3H3N. This pungent-smelling colorless liquid often appears yellow due to impurities. It is an important monomer for the manufacture of useful plastics. In terms of its molecular structure, it consists of a vinyl group linked to a nitrile...