How to Conduct an ATRP
ATRP can be conducted in bulk, solution or a variety of heterogenous media including microemulsion, miniemulsion, emulsion, suspension, dispersion and inverse miniemulsion. The choice of media primarily depends on solubility issues or heat transfer considerations, for example conditionas have to be selected so that the catalyst complex and the product is at least partially soluble in the reaction medium. A solvent is required for the polymerization of acrylonitrile since the polymer is not soluble in the monomer and for a room temperature polymerization of a high Tg polymer to avoid vitrification at high conversion.
When you read the section on Determination of the Redox Potential of Copper Complexes on the Catalyst Development Page you will see that copper based catalysts have been developed for an ATRP where the relative activity of the catalyst complexes cover a range of seven orders of magnitude.(1) Obviously, one cannot select any ligand to form a catalyst complex and assume that the formed catalyst complex is suitable for polymerization of any monomer under any set of conditions. Some selection has to occur, e.g. conditions developed for polymerization of a methacrylate monomer with a pure cuprous bromide/pyridineimine ligand complex as catalyst will not work if the ligand is changed to Me6TREN and reaction conditions and/or catalyst concentration are not changed to take into account the 106 fold higher activity of the Me6TREN based catalyst complex.
A recent review article discussed some of the catalyst based side reaction that can occur when active catalyst complexes are selected for a polymerization.(2) In the paper it was noted that appropriate selection of the catalyst requires a thorough knowledge of concurrent electron transfer reactions that can affect catalyst performance. Special attention should be provided to such processes; including disproportionation, most pronounced in Cu-mediated ATRP, the reduction of radicals to carbanions or oxidation to carbocations, and radical coordination to the metal catalyst which can result in interplay between controlled radical polymerization mechanisms.
A number of starting points that have worked in our laboratories covering preparation of a range of copolymers using ATRP are provided within this segment of the web-page; see menu of left hand side of the page.
The following series of "Starting Points" are only suggestions. The conditions posted on this site have provided well defined polymers in our laboratories but if the run does not go as expected you can/should make adjustments; e.g. add some Cu(II), change the temperature, purge the reaction mix better, add some reducing agent, etc...etc...
(1) Tang, W.; Kwak, Y.; Braunecker, W.; Tsarevsky, N. V.; Coote, M. L.; Matyjaszewski, K. J. Am. Chem. Soc. 2008, 130, 10702-10713.
(2) Tsarevsky, N. V.; Braunecker, W. A.; Matyjaszewski, K. Journal of Organometallic Chemistry 2007, 692, 3212-3222.