Kaminsky catalyst
Encyclopedia
A Kaminsky catalyst is a catalytic system
for alkene polymerization
discovered in 1980. Kaminsky catalysts are based on metallocene
s of group 4 transition metal
s with methylaluminoxane
(MAO). These catalysts are a type of Ziegler-Natta catalyst
, but they are homogeneous and show extremely high activity for polymerization of olefins such as ethylene
, propylene
, and styrene. In addition, the use of chiral
metallocenes that have bridged cyclopentadienyl rings has made possible highly stereoselective (or stereoregular) polymerization of α-olefins. For example, by using metallocene 1 for polymerization of propylene, atactic
polypropylene
is obtained, while C2 symmetric metallocene 2 and Cs symmetric metallocene 3 catalytic systems produce isotactic polymer and syndiotactic macromolecule, respectively.
Kaminsky catalysts are very attractive from the industrial, organometallic, and polymer science
points of view, and they are studied to improve their activity and to achieve high tacticity
and high molecular weight of the produced polymers.
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
for alkene 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...
discovered in 1980. Kaminsky catalysts are based on 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...
s of group 4 transition metal
Transition metal
The term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...
s with 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...
(MAO). These catalysts are a type of 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...
, but they are homogeneous and show extremely high activity for polymerization of olefins such as 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...
, 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...
, and styrene. In addition, the use of chiral
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
metallocenes that have bridged cyclopentadienyl rings has made possible highly stereoselective (or stereoregular) polymerization of α-olefins. For example, by using metallocene 1 for polymerization of propylene, atactic
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...
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...
is obtained, while C2 symmetric metallocene 2 and Cs symmetric metallocene 3 catalytic systems produce isotactic polymer and syndiotactic macromolecule, respectively.
Kaminsky catalysts are very attractive from the industrial, organometallic, and polymer science
Polymer science
Polymer science or macromolecular science is the subfield of materials science concerned with polymers, primarily synthetic polymers such as plastics...
points of view, and they are studied to improve their activity and to achieve high 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...
and high molecular weight of the produced polymers.