ATRP (chemistry)
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2008-07-01T16:00:07Z
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more accurate description of equilibrium reaction, corrected terminology
'''ATRP''' or '''Atom Transfer Radical Polymerization''' is a [[polymerization]] reaction involving [[radical (chemistry)|free radicals]]. It was introduced as an extension to '''ATRA''' or '''Atom Transfer Radical Addition''' by [[Jin-Shan Wang]], [[Krzysztof Matyjaszewski]] (1995) and [[Mitsuo Sawamoto]] [[et al]]. (1994/5). ATRP is a controlled polymerization technique and not a "[[living polymerization]]" because there are always at least a small degree of chain termination events. ATRP enables controlled chain growth for the synthesis of low [[polydispersity index]] polymers in a variety of architectures including copolymers, block copolymers, and stars.
The control in ATRP is achieved by the use of a ligated transition metal catalyst. The catalyst provides an equilibrium of dormant chains with terminal halides which are randomly activated to a radical by halide abstraction to the metal from a dormant chain end. Polymer growth occurs when chains with radical ends react with monomer molecules, increasing the length of the polymer chain. Controlled polymerizations require a very low equilibrium constant favoring dormant chains in order to suppress radical side reactions that would permanently terminate chain ends, and also quick activation/deactivation kinetics to statistically enable a lower polydispersity.
ATRP has been used in the controlled polymerization of many different styrenes, acrylates, and methacrylates, and has had limited success with acrylonitrile, and amides.
[[Image:ATRP_on_styrene.gif|thumb|center|477px|In this scheme, the ATRP with styrene is depicted as an example of ATRP. If all the styrene is reacted (the conversion is 100%) the polymer will have 100 units of styrene built into it. PMDETA stands for N,N,N',N,N pentamethyldiethylenetriamine.]]
==See also==
* [[Heteropolymer]]
* [[Radical (chemistry)]]
==References==
* Fried, Joel, (2003). Polymer Science & Technology (2nd Ed), Chap 2. Prentice Hall. ISBN 0-13-018168-4.
[[Category:polymer chemistry]]
[[de:Atom Transfer Radical Polymerization]]
[[fr:Polymérisation radicalaire par transfert d'atomes]]
[[pl:ATRP]]