Living Radical Polymerization by the RAFT Process

Graeme Moad; Ezio Rizzardo; San H. Thang

doi:10.1071/CH05072

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Living Radical Polymerization by the RAFT Process

Graeme Moad ^A , Ezio Rizzardo ^A and San H. Thang ^A

+ Author Affiliations

- Author Affiliations

^A CSIRO Molecular Science, Bag 10, Clayton South VIC 3169, Australia.
Email: graeme.moad@csiro.au; ezio.rizzardo@csiro.au; san.thang@csiro.au

Graeme Moad obtained his B.Sc.(Hons1) in 1974 and Ph.D. in 1977 from the University of Adelaide in the field of organic free radical chemistry. Between 1977 and 1979 he undertook postdoctoral research at Pennsylvania State University in the field of biological organic chemistry. He joined CSIRO as a research scientist in 1979 and is currently a chief research scientist. Dr Moad is coauthor of the book ‘The Chemistry of Free Radical Polymerization’ which is about to go to a second edition. His research interests lie in the fields of polymer design and synthesis (free radical polymerization, reactive extrusion), polymerization kinetics and mechanism, and most recently polymer nanocomposites.

Ezio Rizzardo is a graduate of the University of New South Wales and received his Ph.D. from the University of Sydney for his studies on the photochemistry of nitro compounds. He joined CSIRO in 1976 after a postdoc at Rice University, RIMAC, and the Australian National University. His CSIRO research has focussed on developing methods for controlling free radical polymerization. For this he has received a number of awards including the RACI Australian Polymer Medal and the CSIRO Chairman’s Gold Medal. Currently he is a CSIRO Fellow and a Fellow of the Australian Academy of Science.

San H. Thang was born in Saigon, Vietnam, in 1954 and came to Australia in 1979 as a refugee. He completed his B.Sc.(Hons) degree in 1983 and Ph.D. in 1987 from Griffith University. He joined CSIRO in 1986 as a research fellow. He then moved to ICI Australia in late 1987 to undertake the challenge of industrial research. He returned to CSIRO in late 1990, and in 1995 he was co-inventor of the RAFT Process. He is currently a senior principal research scientist at CSIRO Molecular Science where his research focusses on the interface between organic and polymer chemistry.

Australian Journal of Chemistry 58(6) 379-410 https://doi.org/10.1071/CH05072
Submitted: 18 March 2005 Accepted: 3 May 2005 Published: 14 June 2005

Abstract

This paper presents a review of living radical polymerization achieved with thiocarbonylthio compounds [ZC(=S)SR] by a mechanism of reversible addition–fragmentation chain transfer (RAFT). Since we first introduced the technique in 1998, the number of papers and patents on the RAFT process has increased exponentially as the technique has proved to be one of the most versatile for the provision of polymers of well defined architecture. The factors influencing the effectiveness of RAFT agents and outcome of RAFT polymerization are detailed. With this insight, guidelines are presented on how to conduct RAFT and choose RAFT agents to achieve particular structures. A survey is provided of the current scope and applications of the RAFT process in the synthesis of well defined homo-, gradient, diblock, triblock, and star polymers, as well as more complex architectures including microgels and polymer brushes.

We are grateful to DuPont Performance Coatings, in particular Charles T. Berge, Michael Fryd, and Robert R. Matheson, for their support of the work carried out at CSIRO Molecular Science. We also thank our many colleagues at CSIRO and other institutions who have contributed to the development of RAFT polymerization; their names are provided in the references.

References

^* The number average molecular weight or molar mass is simply the total weight of the sample divided by the number of molecules in the sample: M_n = ∑ n_iM_i / ∑n_i = ∑w_i / ∑n_i, where n_i is the number of chains of length i, w_i is the weight of chains of length i, and M_i is the molecular weight of a chain of length i. The weight average molecular weight is the sum of the weights of chains of each molecular weight multiplied by their molecular weight divided by the total weight of the sample: M_w = ∑ w_iM_i / ∑ w_i = ∑ n_iM_i² / ∑ n_iM_i. The weight average is always greater than the number average molecular weight. The polydispersity is the ratio of the weight average to the number average molecular weight and, for an ideal radical polymerization, will be 2 for termination by disproportionation or chain transfer, or 1.5 for termination by combination.