Atom Transfer Radical Polymerization
Krzysztof Matyjaszewski* and Jianhui Xia
Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
Received February 15, 2001
Contents
I. Introduction
2921
II. Mechanistic Understandings of Atom Transfer
Radical Polymerization
2923
A. Components 2923
1. Monomers 2923
2. Initiators 2924
3. Catalysts 2924
4. Solvents 2924
5. Temperature and Reaction Time 2925
6. Additives 2925
B. Typical Phenomenology 2925
1. Kinetics 2925
2. Molecular Weight 2926
3. Molecular Weight Distribution 2926
4. Normal and Reverse ATRP 2927
5. Experimental Setup 2927
6. Catalyst Homogeneity 2927
7. Summary and Outlook 2928
C. ATRP Monomers 2928
1. Styrenes 2928
2. Acrylates 2929
3. Methacrylates 2929
4. Acrylonitrile 2930
5. (Meth)acrylamides 2930
6. (Meth)acrylic Acids 2931
7. Miscellaneous Monomers 2931
8. Summary and Outlook 2931
D. ATRP Initiators 2932
1. Halogenated Alkanes 2932
2. Benzylic Halides 2932
3. R-Haloesters 2933
4. R-Haloketones 2933
5. R-Halonitriles 2934
6. Sulfonyl Halides 2934
7. General Comments on the Initiator
Structure in ATRP
2934
8. Summary and Outlook 2935
E. Transition-Metal Complexes 2935
1. Group 6: Molybdenum and Chromium 2935
2. Group 7: Rhenium 2936
3. Group 8: Ruthenium and Iron 2936
4. Group 9: Rhodium 2938
5. Group 10: Nickel and Palladium 2938
6. Group 11: Copper 2939
7. Summary and Outlook 2940
F. Ligand 2941
1. Nitrogen Ligands 2941
2. Phosphorus Ligands 2941
3. Miscellaneous Ligands 2942
4. Summary and Outlook 2942
G. Additives 2942
H. Catalyst Structure 2943
I. Mechanism 2945
J. Overall Elementary Reactions 2947
III. Materials Made by ATRP 2949
A. Functionality 2949
1. Monomer Functionality 2949
2. Initiator Functionality 2952
3. Chain End Functionality 2955
4. Summary and Outlook 2957
B. Composition 2957
1. Gradient/Statistical Copolymers 2958
2. Block Copolymers 2960
3. Inorganic/Organic Hybrids 2969
4. Summary and Outlook 2970
C. Topology 2972
1. Graft Copolymers 2972
2. Grafts from Surfaces 2977
3. Star Polymers 2978
4. Hyperbranched Polymers 2981
5. Summary and Outlook 2983
IV. Conclusions 2983
V. Acknowledgment 2985
VI. References 2985
I. Introduction
The synthesis of polymers with well-defined com-
positions, architectures, and functionalities has long
been of great interest in polymer chemistry. Typi-
cally, living polymerization techniques are employed
where the polymerizations proceed in the absence of
irreversible chain transfer and chain termination.
1-3
Much of the academic and industrial research on
living polymerization has focused on anionic, cationic,
coordination, and ring-opening polymerizations. The
development of controlled/living radical polymeriza-
tion (CRP) methods has been a long-standing goal
in polymer chemistry, as a radical process is more
tolerant of functional groups and impurities and is
the leading industrial method to produce polymers.
4
Despite its tremendous industrial utility, CRP has
not been realized until recently, largely due to the
inevitable, near diffusion-controlled bimolecular radi-
cal coupling and disproportionation reactions.
2921Chem. Rev. 2001, 101, 2921−2990
10.1021/cr940534g CCC: $36.00 © 2001 American Chemical Society
Published on Web 09/12/2001

The past few years have witnessed the rapid
growth in the development and understanding of new
CRP methods.
5,6
All of these methods are based on
establishing a rapid dynamic equilibration between
a minute amount of growing free radicals and a large
majority of the dormant species. The dormant chains
may be alkyl halides, as in atom transfer radical
polymerization (ATRP) or degenerative transfer (DT),
thioesters, as in reversible addition fragmentation
chain transfer processes (RAFT), alkoxyamines, as
in nitroxide mediated polymerization (NMP) or stable
free radical polymerization (SFRP), and potentially
even organometallic species. Free radicals may be
generated by the spontaneous thermal process (NMP,
SFRP) via a catalyzed reaction (ATRP) or reversibly
via the degenerative exchange process with dormant
species (DT, RAFT).
All of the CRP methods, shown in Scheme 1,
include activation and deactivation steps (with rate
constants k
act
and k
deact
), although in RAFT and DT
the scheme may be formally simplified to just the
exchange process with the apparent rate constant
k
exch
. Generated free radicals propagate and termi-
nate (with rate constants k
p
and k
t
), as in a conven-
tional free-radical polymerization. Thus, although
termination occurs, under appropriate conditions its
contribution will be small (less than a few percent of
total number of chains) and these radical polymer-
izations behave as nearly living or controlled systems.
This review will focus on the fundamentals of
transition metal catalyzed atom transfer radical
polymerization (ATRP). We will discuss the current
mechanistic understanding of this process and some
synthetic applications that have resulted in a variety
of well-defined materials. This review covers the
literature from the beginning of this field (1995) until
approximately the end of 2000. We primarily refer
to papers published in peer-reviewed journals, unless
the work appeared in nonpeer-reviewed literature
and was not followed by a full publication.
A general mechanism for ATRP shown in Scheme
2 corresponds to case 2 from Scheme 1. The radicals,
or the active species, are generated through a revers-
ible redox process catalyzed by a transition metal
Krzysztof (Kris) Matyjaszewski was born in Konstantynow, Poland, in 1950.
He obtained his Ph.D. degree in 1976 at the Polish Academy of Sciences
in Lodz, Poland, working in the laboratories of Professor S. Penczek. He
has received his Habilitation Degree in 1985 from Lodz Polytechnic,
Poland. He stayed as a postdoctoral fellow at the University of Florida,
working with Professor G. B. Butler. Since 1985 he has been at Carnegie
Mellon University, where he has served as Chemistry Department Head
(1994−1998) and is currently J. C. Warner Professor of Natural Sciences.
He is also an adjunct professor at the Department of Petroleum and
Chemical Engineering at the University of Pittsburgh and the Polish
Academy of Sciences in Lodz, Poland. He served as Visiting Professor
at the Universities in Paris, Strasbourg, Bordeaux, Bayreuth, Freiburg,
Ulm, and Pisa. He is an editor of Progress in Polymer Science and serves
on seven editorial boards of polymer journals. His main research interests
include controlled/living polymerization with the most recent emphasis on
free-radical systems. In 1995 he developed atom transfer radical
polymerization (ATRP), one of the most successful methods for controlled/
living radical polymerization (CRP) systems. During the last 5 years his
group (25 postdoctoral fellows and 23 graduate and 26 undergraduate
students) has published over 200 papers on ATRP and CRP. He holds
over 20 U.S. and international patents. Close industrial interactions have
been maintained by the ATRP Consortium (13 companies in 1996−2000)
and newly established CRP Consortium (19 companies in 2001−2005).
Research of Matyjaszewski group has received wide recognition, as
evidenced by the ACS Carl S. Marvel Award for Creative Polymer
Chemistry (1995), Elf Chair of French Academy of Sciences (1998),
Humboldt Award for Senior US Scientists (1999), National Professorship
of Poland (2000), Fellowship of ACS Division of Polymeric Materials and
Engineering (2001), ACS Pittsburgh Award (2001), and ACS Award in
Polymer Chemistry (2001).
Jianhui Xia is a Senior Research Scientist in Corporate R&D at 3M
Company in Saint Paul, MN. He received his B.S. degree in Polymer
Chemistry in 1991 from the University of Science and Technology of China
working with Professor Dezhu Ma. He then went to Emory University of
Atlanta, GA, where he obtained his M.S. degree in Organic Chemistry on
asymmetric synthesis from Professor Dennis Liotta. He earned his Ph.D.
degree in Polymer Chemistry in 1999 on controlled/“living” radical
polymerization at Carnegie Mellon University under the direction of
Professor Krzysztof Matyjaszewski. His current research interests include
the controlled synthesis of novel polymeric materials.
Scheme 1. General Scheme of CRP Methods
2922 Chemical Reviews, 2001, Vol. 101, No. 9 Matyjaszewski and Xia