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Macromolecular Division (IV)


Number: 2000-028-1-400

Title: Critically evaluated termination rate coefficients for free-radical polymerization. 1. Current status, evaluation of experimental methods, data for styrene and methyl methacrylate

Task Group
Greg Russell

Members: Sabine Beuermann, Michael Buback, Mark Egorov, Robert Gilbert, Robin Hutchinson, Vladimir Kaminsky, Oskar Friedrich Olaj, Philipp Vana, and Gerhard Zifferer
(added in 2003)
Christopher Barner-Kowollik, Takeshi Fukuda, Atsushi Goto, Bunichiro Yamada, Per Zetterlund, Graeme Moad and Hans Heuts.

To begin the task of providing critically evaluated ("benchmark") values of termination rate coefficients for free-radical polymerization.

Free-radical polymerization (FRP) has always been a scientifically and commercially important field. This importance is set to increase even further due to recent advances such as the development of "controlled radical polymerization". Hence it is of great benefit for both science and industry to be able to model the kinetics of FRP systems. Such modeling is dependent on the availability of reliable values of rate coefficients. Unfortunately FRP systems have proven to be difficult subjects for investigations aimed at determining accurate rate coefficients. However recently the IUPAC Working Party on "Modeling of Polymerization Kinetics and Processes" has made considerable progress in delivering critically evaluated propagation rate coefficients, kp, for FRP systems.

> See Related Publications

But the situation is not so well developed for termination rate coefficients, kt, which are equally as fundamental and important as kp. Therefore there is great necessity for the progress made with regard to kp to be matched on the termination front. It is the aim of this project to make such progress. To do this there is first of all the need to make workers aware of the subtleties involved in studying and describing the termination reaction. Secondly there needs to be carried out an evaluation of methods for determining kt, and for agreement to be arrived at regarding the strengths and weaknesses of each method. Finally, we will apply our conclusions to data from the initial stages of bulk polymerizations of styrene and methyl methacrylate, two otherwise well characterized systems, so as to come up with critically evaluated kt for these systems.

The first of our three objectives was realised in the form of the following publication:

"Critically evaluated termination rate coefficients for free-radical polymerization", M. Buback, M. Egorov, V. Kaminsky, O.F.Olaj, G.T. Russell, P. Vana, G. Zifferer, Macromol. Chem. Phys. 203, 2570-2582 (2002)
> abstract (MCP website)

Since then there have been two specific gatherings of taskgroup members: (1) On 20 August 2002, during the 224th ACS meeting in Boston; (2) On 17 November 2003, at the Institute of Physical Chemistry, University of Göttingen. These discussions facilitated the meeting of the second of our three objectives through the following publication:

"Critically evaluated termination rate coefficients for free-radical polymerization: experimental methods", C. Barner-Kowollik, M. Buback, M. Egorov, T. Fukuda, A. Goto, O.F. Olaj, G.T. Russell, P. Vana, B. Yamada and P.B. Zetterlund, Prog. Polym. Sci. 2005, in press

The third and final task of establishing and documenting benchmark termination rate coefficients for styrene and methyl methacrylate bulk polymerizations was initiate in July 2004, and it is anticipated that this task will be completed by Hans Heuts, Michael Buback and Greg Russell, acting on information provided by most other taskgroup members, over the middle months of 2005.

Last update: 21 March 2005

<project announcement published in Chem. Int. 23(3) 2001>


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