Coordination Polymerization
“Coordination polymerizationis a form of addition polymerization in which monomer adds to a growing macromolecule through an organometallic active center. The development of this polymerization technique started in the 1950s with heterogeneous Ziegler-Natta catalysts based on titanium tetrachloride and an aluminium co-catalyst such as methylaluminoxane. Coordination polymerization has a great impact on the physical properties of vinyl polymers such as polyethylene and polypropylene 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. Coordination type polymers are also stereoregular and can be isotactic or syndiotactic instead of just atactic. This tacticity introduces crystallinity 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)” (Wikipedia, Coordination Polymerization, 11/15/2010)
Review Articles
11/12/2010
Transition metal catalysts for controlled radical polymerization
(959-1021) Progress in Polymer Science 35 #8 (2010)
In the mid 1990s, it was discovered that certain cobalt, ruthenium and copper complexes can effectively control the radical polymerization of a number of polar olefins, allowing for the synthesis of complex macromolecular architectures, This article presents an organized and detailed overview of the most significant developments in the use of transition metal compounds to initiate, mediate and control radical polymerization, i.e., atom transfer radical polymerization or organometallic mediated radical polymerization. The catalysts have been classified according to the group of the periodic table to which the relative metal centers belong.
11/12/2010
Transition metal catalysts for controlled radical polymerization
Review Article
(959-1021) Progress in Polymer Science 35 #8 (2010)