Microwave-Assisted Polymer Synthesis: Recent Developments in a ...

Microwave-Assisted Polymer Synthesis: Recent Developments in ...
reaction mixture, whereby the use of good microwave
absorbing solvents results in very fast heating. [5] Besides
the advantages of fast and homogeneous heating as well
as the possible high-temperature chemistry, non-thermal
microwave effects due to specific heating of polar intermediates
have been observed, e.g., leading to modified
Richard Hoogenboom was born in 1978 in Rotterdam
(The Netherlands). In 2001 he obtained
his M.Sc. degree in chemical engineering at the
Eindhoven University of Technology, whereby his
undergraduate research was performed in the
group of Bert Meijer (Eindhoven, The Netherlands).
During the studies, he performed an internship
within the group of Andrew Holmes (Cambridge,
United Kingdom). In 2005, he obtained his Ph.D.
under supervision of Ulrich S. Schubert (Eindhoven,
The Netherlands) focusing on supramolecular
initiators for controlled polymerization
techniques, automated parallel synthesis of
well-defined polymers and microwave irradiation
in polymer chemistry. Currently, he is working
as project leader for the Dutch Polymer
Institute (DPI) with a major focus on the use
of high-throughput experimentation and microwave
irradiation for living/controlled polymerization
techniques.
Ulrich S. Schubert was born in Tübingen in 1969.
He studied chemistry at the Universities of Frankfurt
and Bayreuth (both Germany) and the Virginia
Commonwealth University, Richmond (USA).
His Ph.D. work was performed under the supervision
of Professor Eisenbach (Bayreuth, Germany)
and Professor Newkome (Florida, USA). In 1995 he
obtained his doctorate with Prof. Eisenbach. After
a postdoctoral training with Professor Lehn at the
Université Strasbourg (France) he moved to the
Technische Universität München (Germany) to
obtain his habilitation in 1999 (with Professor
Nuyken). From 1999 to spring 2000 he held a
temporal position as a professor at the Center
for NanoScience at the Universität München
(Germany). Since Summer 2000 he is Full-
Professor at the Eindhoven University of Technology
(Chair for Macromolecular Chemistry and
Nanoscience). From 2003 on he is member of
the management team of the Dutch Polymer
Institute. His awards include the Bayerischen
Habilitations-Förderpreis, the Habilitandenpreis
of the GDCh (Makromolekulare Chemie), the
Heisenberg-Stipendium of the DFG, the Dozenten-
Stipendium of the Fonds der Chemischen Industrie
and a VICI award of NWO. The major focus of
the research interest of his relates to organic
heterocyclic chemistry, supramolecular materials,
combinatorial material research, nanoscience and
tailor-made macromolecules.
selectivities and enabling reactions that cannot be performed
with thermal heating. [6] These non-thermal microwave
effects are thought to arise from specific microwave
absorption by polar components of a reaction making
them more reactive under microwave irradiation when
compared to thermal heating.
The use of microwave irradiation in polymer chemistry
is an emerging field of research that we reviewed in
2004. [7] Up to that moment, many investigations of
microwave-assisted polymerizations were conducted in
domestic microwave ovens making the reproducibility
and safety of the experiments doubtful due to insufficient
temperature control. However, the development of commercial
microwave synthesizers with excellent temperature
control significantly improved the reliability of the
reported microwave-assisted polymerizations. As a result,
the number of publications on microwave-assisted polymerizations
per year has shown a rapid expansion
(Figure 1). [8] In fact, a similar figure in the previous review
showed maximum 90 publications per year, which almost
doubled in the last two years.
In the current review, the progress in the field of
microwave-assisted polymer synthesis since the previous
review will be discussed with a main focus on step-growth
polymerizations, ring-opening polymerization, and (controlled)
radical polymerizations. Special attention will be
given to the occurrence of non-thermal microwave effects,
which is still a controversial topic.
Step-Growth Polymerization
Step-growth polymerizations are based on the coupling of
two multifunctional, mostly bifunctional, monomers.
The resulting coupled product also contains the functional
groups and thus reacts in the same manner as the
Figure 1. Number of publications on microwave-assisted
polymerizations per year. [8]
Macromol. Rapid Commun. 2007, 28, 368–386
ß 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.mrc-journal.de 369