Table Of ContentControlled/Living Radical
Polymerization:
Progress in ATRP
In Controlled/Living Radical Polymerization: Progress in ATRP; Matyjaszewski, K.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
In Controlled/Living Radical Polymerization: Progress in ATRP; Matyjaszewski, K.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
ACS SYMPOSIUM SERIES 1023
Controlled/Living Radical
Polymerization:
Progress in ATRP
Krzysztof Matyjaszewski, Editor
Carnegie Mellon University
Sponsored by the
ACS Division of Polymer Chemistry, Inc.
ACS Petroleum Research Foundation
Arkena, Bayer, Boston Scientific, Ciba, CIP, Dionex, DSM,
Elsevier, Evonik, General Electric, JSR, Lion,
Mitsui Chemicals, National Starch, PPG and Sumitomo
American Chemical Society, Washington DC
In Controlled/Living Radical Polymerization: Progress in ATRP; Matyjaszewski, K.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
Library of Congress Cataloging-in-Publication Data
Controlled/living radical polymerization : progress in ATRP / Krzysztof
Matyjaszewski, editor.
p. cm. -- (ACS symposium series; 1023)
Includes bibliographical references and index.
ISBN 978-0-8412-6995-8 (alk. paper)
1. Polymerization--Congresses. 2. Free radical reactions--Congresses. I.
Matyjaszewski, K. (Krzysztof)
QD281.P6C6555 2009
547'.28--dc22
2009020531
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In Controlled/Living Radical Polymerization: Progress in ATRP; Matyjaszewski, K.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
Foreword
The ACS Symposium Series was first published in 1974 to provide a
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In Controlled/Living Radical Polymerization: Progress in ATRP; Matyjaszewski, K.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
Preface
This book and an accompanying volume are addressed to chemists
who are interested in radical processes and especially in controlled/living
radical polymerization. They summarize the most recent
accomplishments in the field.
The two volumes comprise the topical reviews and specialists'
contributions presented at the American Chemical Society Symposium
entitled Controlled/Living Radical Polymerization that was held in
Philadelphia, Pennsylvania, August 17-21, 2008. The Philadelphia
Meeting was a sequel to the previous ACS Symposia held in San
Francisco, California, in 1997, in New Orleans, Louisiana, in 1999, in
Boston, Massachusetts, in 2002 and in Washington, DC, in 2005. They
were summarized in the ACS Symposium Series Volume 685,
Controlled Radical Polymerization, Volume 768, Controlled/Living
Radical Polymerization: Progress in ATRP, NMP and RAFT, Volume
854 Advances in Controlled/Living Radical Polymerization and Volume
944, Controlled/Living Radical Polymerization: From Synthesis to
Materials. The Philadelphia Meeting was very successful with 90
lectures and 123 posters presented. This illustrates a continuous growth
in comparison with the San Francisco Meeting (32 lectures and 35
posters), the New Orleans (50 lectures and 50 posters), the Boston
Meeting (80 lectures and 79 posters) and with the Washington Meeting
(77 lectures and 119 posters).
The fifty chapters submitted for publication in the ACS Symposium
series could not fit into one volume and therefore we decided to split
them into two volumes. In order to balance the size of each volume we
did not divide the chapters into volumes related to mechanisms and
materials but rather to those related to atom transfer radical
polymerization (ATRP) and to other controlled/living radical
polymerization methods: reversible-addition fragmentation transfer
(RAFT) and other degenerative transfer techniques, as well as stable free
radical polymerizations (SFRP) including nitroxide mediated
polymerization (NMP) and organometallic mediated radical
polymerization (OMRP).
The first chapter in this volume provides an overview of the current
status of controlled/living radical polymerization (CRP) systems. The
following three chapters discuss important issues relevant to all radical
polymerization methods. The mechanistic and kinetic topics of ATRP are
xi
In Controlled/Living Radical Polymerization: Progress in ATRP; Matyjaszewski, K.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
covered in eight chapters. The macromolecular architecture, various
hybrids and bio-related polymers prepared by ATRP are discussed in the
next six chapters, Characterization and materials aspects of ATRP
polymers are covered in six chapters, whereas the last four chapters
discuss industrial applications of ATRP.
The next volume contains 10 chapters on mechanisms and kinetics of
RAFT, other degenerative transfer processes, NMP and OMRP. They are
followed by six chapters devoted to molecular architecture accessible by
these techniques. Various materials aspects of the resulting polymers are
covered in six chapters. The last two chapters present commercial
application of polymers prepared by NMP and RAFT (or MADIX).
Fifty chapters published in two volumes show that CRP has made a
significant progress within the last decade. New systems have been
discovered; substantial progress has been achieved in understanding the
mechanism and kinetics of reactions involved in all CRP systems.
Significant progress has been made towards a comprehensive
relationship between molecular structure and macroscopic properties.
Some commercial applications of CRP were announced at the
Philadelphia Meeting and it is anticipated that many new products will
be soon on the market.
The financial support for the symposium from the following
organizations is acknowledged: ACS Division of Polymer Chemistry,
Inc., ACS Petroleum Research Foundation, Arkema, Bayer, Boston
Scientific, Ciba, CIP, Dionex, DSM, Elsevier, Evonik, General Electric,
JSR, Lion, Mitsui Chemicals, National Starch, PPG and Sumitomo. The
excellent editorial assistance from Joyce Von Vreckin is gratefully
acknowledged.
Krzysztof Matyjaszewski
Department of Chemistry
Carnegie Mellon University
4400 Fifth Avenue
Pittsburgh, PA 15213
In Controlled/Living Radical Polymeriza xtioini: Progress in ATRP; Matyjaszewski, K.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
Chapter 1
Controlled Radical Polymerization: State of
the Art in 2008
Krzysztof Matyjaszewski
Center for Macromolecular Engineering, Department of Chemistry,
Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
State of the art of Controlled Radical Polymerization (CRP) is
presented. Stable free radical polymerization, atom transfer
radical polymerization, and degenerate transfer processes,
including reversible addition fragmentation transfer are
discussed as the most successful CRP techniques. They
provide access to new materials from many commercially
available monomers under undemanding conditions. Better
understanding of the structure-reactivity relationship for the
various CRPs and a deeper insight into the mechanistic
features can expand range of polymerizable monomers and
polymer architectures. Development of a precise relationship
between macromolecular structure, processing and final
properties of materials will help to find new applications and
accelerate commercialization of CRP products.
Controlled/living radical polymerization (CRP) is among the most rapidly
1-3
developing areas of chemistry and polymer science. The research on CRP
encompasses very fundamental mechanistic studies, synthetic polymer
chemistry, many detailed physical chemistry studies to evaluate properties of
prepared materials and also search for new applications to commercialize CRP
products.
During the last fifteen years an explosive increase has been observed in the
number of publications on CRP, including a dramatic increase in the number of
4-7
patent applications and several symposia devoted partially, or entirely, to CRP.
Figure 1 illustrates results of a recent SciFinder Scholar search using the
following terms: controlled radical polymn or living radical polymn
© 2009 American Chemical Society 3
In Controlled/Living Radical Polymerization: Progress in ATRP; Matyjaszewski, K.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
4
7000 SUM CRP
SUM ATRP
6000 SUM SFRP
SUM DT
5000
4000
3000
2000
1000
0
Year
Figure 1. Results of SciFinder Search on various CRP systems as of November
15, 2008. Detail explanation of terms is provided in the text.
(“CRP&LRP” in Figure 1), ATRP or atom transfer (radical) polymn (“ATRP
only”, this search does not include terms such as metal mediated or metal
catalyzed (living) radical polymerization), NMP or SFRP or nitroxide mediated
polymn or stable free polymn (“SFRP&NMP”) and RAFT or reversible addition
transfer or degenerative transfer or catalytic chain transfer
(“RAFT&DT&CT”). The latter two terms were refined with a term radical
polymn since they coincide with other common chemical names such as N-
methylpyrrolidone or raft-associated proteins. In summary, since 1995 over
12,000 papers have been published on various CRP systems and more than half
of that on ATRP. During the last four years, about 3 papers per day are
published daily on ATRP. There is also another trend which can be deduced
from Figure 1. Progressively more papers are published on specific techniques
of CRP rather than referring to a generic CRP or LRP terms.
All CRP methods rely on a dynamic equilibration between tiny amounts of
propagating radicals and various types of dormant species. The essence of the
process is a rapid reversible deactivation of growing radicals. Radicals always
terminate and therefore CRP is never “living” in the pure sense of the living
polymerization definition. Indeed, IUPAC recommends to avoid using term
“living” for the radical polymerization and suggests to use the term “controlled
reversible deactivation radical polymerization”.
At the same rate of polymerization (whether it is a conventional process or
CRP), the same radical concentration is present and essentially the same number
In Controlled/Living Radical Polymerization: Progress in ATRP; Matyjaszewski, K.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
Cumulative Number of Publications
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
5
(concentration) of chains terminate. However, in the conventional process, all
-3
chains are terminated (e.g., 10 M), whereas in CRP, as a result of the large total
-1
concentration of chains (e.g., 10 M of dormant and active/terminated), the
-3
fraction of terminated chains (10 M) is much smaller (typically between 1 and
10%). The remaining chains are in the dormant state, capable of reactivation,
functionalization, chain extension to form block copolymers, etc. Since the
proportion of terminated chains in the final product is small, they often do not
affect the physical properties of the targeted materials.
Perhaps the most important difference between conventional and CRP
processes is the approach to the steady state. In a conventional radical
polymerization, steady state is achieved by balancing rate of initiation and
termination. In order to prepare polymers with high molecular weights (Mn
~100,000, i.e. with DP~1000), propagation rate must be 1000 times higher than
termination rate. Consequently initiation must be also 1000 times slower than
propagation. This prevents synthesis of well defined polymers. In order to
prepare polymers with controlled molecular weights (DPn=Δ[M]/[I]0) and
narrow molecular weight distribution, the rate of initiation should be comparable
to propagation. In systems controlled by the persistent radical effect, such as
ATRP and SFRP, steady state is achieved by balancing rates of activation and
deactivation rather than initiation and termination. For the first time in radical
polymerization, this allows decoupling the rates of initiation and termination.
Termination must still be thousands times slower than propagation, but initiation
can now be as fast as propagation.
The key to attaining control in CRP is the reversible deactivation of radicals
(or intermittent activation of dormant species). Their interconversion should be
fast, to provide a similar probability of growth for all chains and, consequently,
form polymers with narrow molecular weight distribution. Fine tuning of the
exchange rate offers a possibility to design molecular weight distribution and
also influence polymer properties. Such polymers will preserve chain end
functionalities, will be capable of cross-propagation and block copolymer
formation. On the other hand, due to continuously occurring termination,
polymers may loose functionality and still keep low polydispersity (especially if
termination occurs at high conversion by disproportionation). Thus, a correlation
between polydispersity and functionality in CRP is relatively weak.
Figure 2 shows three approaches to the intermittent activation required for
CRP. SFRP and ATRP employ the persistent radical effect.
SFRP (exemplified by nitroxide mediated polymerization, NMP, or
organometallic radical polymerization, OMRP) relies on spontaneous homolytic
cleavage of covalent species. Deactivators are typically paramagnetic species
but compounds with even number of electrons could be also used (e.g.
thioketone mediated polymerization, TKMP). The homolytic cleavage can be
catalyzed as in ATRP. Both these processes rely on persistent radical effect
(PRE). The alternative approach utilizes a degenerative transfer (DT)
mechanism with alkyl iodides, dithioesters/xanthates (reversible addition
fragmentation transfer, RAFT or MADIX) or organometallic species as transfer
agents. DT systems do not obey PRE kinetics but follow a conventional radical
polymerization with a steady state established by balancing initiation and
termination rates rather than activiation/deactivation.
In Controlled/Living Radical Polymerization: Progress in ATRP; Matyjaszewski, K.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
