Wolfgang H. Binder talks with
ScienceWatch.com and answers a few questions about
this month's New Hot Paper in the field of
Chemistry. The author has also sent along images of
Article Title: 'Click' chemistry in polymer and
Journal: MACROMOL RAPID COMMUN
Year: JAN 5 2007
* Vienna Univ Technol, Inst Appl Synthet Chem, Div Macromol
Chem, Getreidemarkt 9-163-MC, A-1060 Vienna, Austria.
* Vienna Univ Technol, Inst Appl Synthet Chem, Div Macromol
Chem, A-1060 Vienna, Austria.
Why do you think your paper is highly
The paper on "click"-chemistry in polymer and materials-science1
provides an overview on the use of a newly discovered reaction for
application in polymer and material science. The reaction basically is an
old one (i.e.: a Huisgen-type 1,3-dipolar cycloaddtion reaction), but was
re-discovered as a catalytic-high-yielding reaction in 2001-2002 by Meldal
et al. 2, 3 and Sharpless et al.4
by using Cu(I)-salts as catalysts.
Scheme 1 Basic reaction of the
As the reaction is highly ubiquitous (i.e.: yield of product often more
than 99%, substrate and solvent independent reaction progress) it
represents a landmark in
polymer, material, and supramolecular science, where
reactions with such completeness and effectiveness are difficult to
conduct. The method brings polymer science to a standard of organic
chemistry in terms of impurities and completeness, most of all in the
synthesis of highly defined polymer-molecules and materials.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
"Click"-chemistry is a valuable tool in polymer science for the efficient
linkage of functional entities, oligomers, or polymers, yielding access to
functional homo-, block-, star-, graft-polymers as well as higher polymeric
architectures (dendrimers, hyperbranched polymers, supramolecular polymers,
gels, polymer brushes).
Besides other efficient-"click"-reactions, the copper-(I)-catalyzed
1,3-dipolar-azide/alkine-cycloaddition reaction has emerged as the method
of choice for this and related purposes. The main advantage in relation to
conventional linking reactions are (a) quantitative yields (b) mild
reaction conditions (c) solvent and substrate insensitivity (d)
high-yielding reactions under both homogeneous and heterogeneous reaction
Shortly after 2001, the azide/alkine-"click"-reaction was discovered as a
metal-catalyzed (Cu(I))-1,3-dipolar cycloaddition reaction
(Huisgen-reaction), revealing many applications in bioorganic and organic
chemistry. This reaction proved superior over others since (a) the two
reactants (terminal azide, reacting with a terminal alkine) are of
individual low reactivity and (b) as only a catalytic quantity of a metal
salt (Cu(I)) was required to accelerate the reaction. The reaction showed
all features of a "click"-reaction including substrate insensitivity, ease,
wide scope, solvent-insensitivity, and quantitative nature. Subsequently,
the first published applications of this reaction in polymer science were
published around 2004,5-10 quickly demonstrating the high
efficiency of this process, coupled with a high functional group tolerance
and solvent insensitivity (the reaction is also highly active in water),
working equally well under homogeneous and heterogeneous conditions.
Thus the azide/alkine-"click"-reaction emerged as a solution to many of the
types of problems encountered in polymer science for a long time, such as:
(a) a poor degree of functionalization with many conventional methods,
especially when involving multiple functional groups (i.e.: at graft-,
star-, block copolymers; dendrimers as well as on densely packed surfaces
and interfaces) (see Figure 1); (b) purification problems associated with
the often emerging partially functionalized mixtures; (c) incomplete
reaction on surfaces and interfaces; and (d) harsh reaction conditions of
conventional methods, often leading to the break-up of associates and
assemblates, in particular in the newly emerging supramolecular sciences.
Therefore, the Cu(I)-catalyzed azide/alkine-"click"-reaction is a highly
valuable tool for any quantitative polymeric postmodification reaction.
Would you summarize the significance of your paper
in layman's terms?
A unified chemical reaction, which efficiently links molecules under
complete and quantitative reaction, irrespective of the solvent and the
substrate (molecule) even at room-temperature. Copper(I)-salts are required
as catalysts to accelerate the reaction. In contrast to many previous
chemical reactions, this one can be used at any time without great effort.
How did you become involved in this research, and
were there any problems along the way?
I had heard a talk from one of the inventors of this reaction
K. Barry Sharpless of The Scripps Research Institute), who entirely
focused on the use of this reaction in organic synthesis (Vienna, 2003).
As this reaction seemed a solution to many problems encountered by us in
previous years, we immediately probed the reaction and found it
extremely useful for application in polymer science. From thereon we
successfully applied this reaction1, 9, 11-24 and have gained
fast approach to polymers for supramolecular science,12-14, 16, 18,
24, 25 surfaces,16, 18, 24 bioencapsulation,12,
23 nanoparticles,22, 26 and nanotechnology.16,
27 A new review11 covers the topic in a special issue.
Where do you see your research leading in the
Future research will deal will applications of this reaction for biomedical
polymers, in particular, materials located at the interface of biological-,
microelectronic-, and chemical polymers. Thus, new materials for solar
cells or biomembranes are currently investigated in our laboratory, which
are prepared via the "click"-chemistry method.
Do you foresee any social or political
implications for your research?
The reaction leads to a faster growth of polymer science due to the ease of
generating defined polymeric molecules with specific function. Therefore,
modern areas at the borderline between medicine, polymer science, and
material science will have a faster development due to better synthetic
methodologies. As an example, the highly complex interface between
structural biology and synthetic polymer chemistry can be investigated much
better. In particular, fields of superglues/superstrong adhesives,
biomedical polymers, and microelectronics will benefit from this discovery.
Prof. Dr. Wolfgang Binder
Professor of Macromolecular Chemistry
Faculty of Natural Sciences II/Institute of Chemistry
Martin-Luther University Halle-Wittenberg
Halle-Wittenberg, Saxony-Anhalt, Germany
1. Binder WH, Sachsenhofer R, "'Click' Chemistry in Polymer and Materials
Science," Macromol. Rapid Commun. 28 (1): 15-54, 2007.
2. Meldal M, Tornoe CW, "Peptidotriazoles: Copper(I)-Catalyzed 1,3-Dipolar
Cycloadditions on Solid-Phase," Proceedings of the Second International
and the Seventeenth American Peptide Symposium 263-64, 2001.
3. Tornoe CW, Christensen C, Meldal M, "Peptidotriazoles on Solid Phase:
[1,2,3]-Triazoles by Regiospecific Copper(I)-Catalyzed 1,3-Dipolar
Cycloadditions of Terminal Alkynes to Azides," J. Org. Chem. 67
(9): 3057-64, 2002.
4. Rostovtsev VV, Green LG, Fokin VV, Sharpless KB, "A Stepwise Huisgen
Cycloaddition Process: Copper(I)-Catalyzed Regioselective "Ligation" of
Azides and Terminal Alkynes," Angew Chem. Int. Ed. 41 (14):
5. Smet M, Metten K, Dehaen W, "Synthesis of new AB2 Monomers for
polymerization to hyperbranched polymers by 1,3-dipolar cycloaddition,"
Collect. Czech. Chem. Commun. 69: 1097-1108, 2004.
6. Díaz DD, Punna S, Holzer P, McPherson AK, Sharpless KB, Fokin VV,
Finn MG, "Click chemistry in materials synthesis. 1. Adhesive polymers from
copper-catalyzed azide-alkyne cycloaddition" J. Polym. Sci., Part A:
Polym. Chem. 42 (17): 4392-4403, 2004.
7. Scheel AJ, Komber H, Voit BI, "Novel Hyperbranched
Poly([1,2,3]-triazole)s Derived from AB2 Monomers by a 1,3-Dipolar
Cycloaddition," Macromol. Rapid Commun. 25 (12): 1175-80, 2004.
8. Helms B, Mynar JL, Hawker CJ, Frechet JMJ, "Dendronized Linear Polymers
via 'Click Chemistry,'" J. Am. Chem. Soc. 126 (46): 15020-21,
9. Binder WH, Kluger C, "Combining Ring-Opening Metathesis Polymerization
(ROMP) with Sharpless-Type "Click" Reactions: An Easy Method for the
Preparation of Side Chain Functionalized Poly(oxynorbornenes),"
Macromolecules 37 (25): 9321-30, 2004.
10. Tsarevsky NV, Bernaerts KV, Dufour B, DuPrez FE, Matyjaszewski K,
"Well-Defined (Co)polymers with 5-Vinyltetrazole Units via Combination of
Atom Transfer Radical (Co)polymerization of Acrylonitrile and "Click
Chemistry"-Type Postpolymerization Modification," Macromolecules
37 (25): 9308-13, 2004.
11. Binder WH, Sachsenhofer R, "'Click'-Chemistry in Polymer and Material
Science: An Update," Macromol. Rapid. Commun. 29 (12-13): 952-81,
12. Binder, W. H.; Sachsenhofer, R., Polymersome/Silica Capsules by
"Click"-Chemistry. Macromo. Rapid. Commun. 29 (12-13): 1097-1103,
13. Kluger C, Binder WH, "Functionalized
poly(oxanorbornene)-block-copolymers: Preparation via
ROMP/click-methodology," J. Polym. Sci., Part A: Polym. Chem. 45
(3): 485-99, 2007.
14. Binder WH, Gloger D, Weinstabl H, Allmaier G, Pittenauer E, "Telechelic
Poly(N-isopropylacrylamides) via Nitroxide-Mediated Controlled
Polymerization and "Click" Chemistry: Livingness and "Grafting-from"
Methodology," Macromolecules 40 (9): 3097-3107, 2007.