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Angewandte
Communications
Rewritable Materials
Rewritable Polymer Brush Micropatterns Grafted by Triazolinedione
Click Chemistry
Oliver Roling, Kevin De Bruycker, Benjamin Vonhçren, Lucas Stricker, Martin Kçrsgen,
Heinrich F. Arlinghaus, Bart Jan Ravoo,* and Filip E. Du Prez*
Abstract: Triazolinedione (TAD) click reactions were com-
bined with microcontact chemistry to print, erase, and reprint
polymer brushes on surfaces. By patterning substrates with
a TAD-tagged atom-transfer radical polymerization initiator
(ATRP-TAD) and subsequent surface initiated ATRP, it was
possible to graft micropatterned polymer brushes from both
alkene- and indole-functionalized substrates. As a result of the
dynamic nature of the Alder–ene adduct of TAD and indole at
elevated temperatures, the polymer pattern could be erased
while the regenerated indole substrate could be reused to print
new patterns. To demonstrate the robustness of the method-
ology, the write–erase cycle was repeated four times.
pattern resolution, high versatility, and preparative ease and
simplicity. For example, mCP has been used to form patterned
SAMs of polymerization initiators on gold surfaces employing
thiols as anchoring moieties. Subsequent surface initiated
polymerization results in microstructured polymer
brushes.[18,19] Microcontact chemistry (mCC) is a variation of
mCP in which a substrate, coated with a reactive layer, is
brought into close conformal contact with an elastomeric
stamp, which is soaked with an ink containing complementary
reactive groups, thus leading to surface functionalization by
a chemical reaction exclusively in the area of contact. Click
reactions in particular were found to be versatile for surface
functionalization via mCC.[20,21] While most of the examples
cited above aim for a robust and irreversible surface
functionalization, only very few reactions offer stable (that
is, covalent) yet dynamic grafting with switchable surface
properties. One example is the elegant photoclick system
reported by Popik and Arumugam, which works very well for
small molecules.[22] Barner-Kowollik and co-workers used the
reversible nature of Diels–Alder reactions between reversible
addition fragmentation transfer (RAFT) agents and cyclo-
pentadienyl moieties to graft polymer brushes onto silicon
substrates in a non-patterned fashion to detach them at
elevated temperatures and thus switch surface properties
owing to reversible grafting.[23]
T
he fabrication of micro- and nanostructured polymer
substrates is a key focus of materials science, leading to
devices with potential applications in information storage,[1]
electronic devices,[2,3] biosensing, and antifouling coatings.[4–11]
In this context, polymer brushes grown by the “grafting-from”
approach are especially attractive, because an excellent
control of film thickness is given and high grafting densities
are accessible. In principle any chemical functional group can
be incorporated into the brushes, as a wide variety of
monomers is available. To date, many different polymer
materials have been used in combination with various
lithography techniques to tailor surface properties, yielding
substrates with enhanced functions.[12–15] One type of soft
lithography that has been frequently used for the generation
of patterned self-assembled monolayers (SAMs) is micro-
contact printing (mCP).[16,17] In mCP, a SAM is patterned by
means of a selective transfer of an ink from a patterned stamp
to a substrate exclusively in the area of contact. mCP features
a set of advantageous properties such as low cost and low
consumption of material, large and fast area patterning, high
We recently employed Diels–Alder and Alder–ene reac-
tions of various reactive triazolinediones (TAD) with a range
of dienes and alkenes to produce block copolymers, cross-
linked plant-oil-based materials, and also covalently linked
layer-by-layer assemblies on surfaces (Scheme 1a).[24–26]
These TAD click reactions proceed at room temperature
with high reaction rates and are often complete within
seconds without the need for a catalyst, irradiation, or other
external stimuli. Moreover, if an indole is used instead of
a simple alkene, reversibility of the Alder–ene adduct is
[*] O. Roling, B. Vonhçren, L. Stricker, Prof. Dr. B. J. Ravoo
Organisch-Chemisches Institut, Center for Soft Nanoscience and
Graduate School of Chemistry, Westfälische Wilhelms-Universität
Münster
Corrensstrasse 40, 48149 Münster (Germany)
E-mail: b.j.ravoo@uni-muenster.de
M. Kçrsgen, H. F. Arlinghaus
Physikalisches Institut, Westfälische Wilhelms-Universität Münster
Wilhelm-Klemm-Strasse 10, 48149 Münster (Germany)
K. De Bruycker, F. E. Du Prez
Department of Organic and Macromolecular Chemistry
Ghent University
Krijgslaan 281 S4-bis, B-9000 Gent (Belgium)
E-mail: filip.duprez@ugent.be
Scheme 1. a) The TAD click reaction with an indole, which is reversible
at elevated temperatures. b) Example of a transclick reaction: after the
TAD–indole adduct is cleaved, the released TAD is captured by a diene.
Supporting information for this article is available on the WWW
13126
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 13126 –13129