Various polyimides and polyamides have recently been prepared via hydrothermal synthesis in nothing but H2O under high‐pressure and high‐temperature conditions. However, none of the prepared polymers feature a truly conjugated polymer backbone. Here, we report on an expansion of the synthetic scope of this straightforward and inherently environmentally friendly polymerization technique to the generation of conjugated polymers. Selected representatives of two different polymer classes, pyrrone polymers and polybenzimidazoles, were generated hydrothermally. We present a mechanistic discussion of the polymer formation process as well as an electrochemical characterization of the most promising product.
The synthesis and
thermoresponsive properties of surface-attached
poly(
N
-isopropylacrylamide)-
co
-
N
,
N
′-methylene bisacrylamide (PNIPAM-
co
-MBAM) networks are investigated. The networks are formed
via
SI-ARGET-ATRP (“grafting-from”) on thiol-based
initiator-functionalized gold films. This method is reliable, well
controlled, fast, and applicable to patterned surfaces (
e.g.
, nanopores) for networks with dry thicknesses >20 nm. Surface-attached
PNIPAM-
co
-MBAM gels are swollen below their volume
phase transition temperature but above collapse without complete expulsion
of water (retain ∼50 vol %). The swelling/collapse transition
is studied using complementary SPR and QCMD techniques. The ratio
between swollen and collapsed heights characterizes the thermoresponsive
behavior and is shown to not depend on network height but to vary
with MBAM content. The higher the proportion of the crosslinker, the
lower the magnitude of the phase transition, until all responsiveness
is lost at 5 mol % MBAM. The temperature range of the transition is
broadened for more crosslinked PNIPAM-
co
-MBAM gels
but remains centered around 32 °C. Upon reswelling, less crosslinked
networks display sharp transitions, while for those containing ≥3
mol % MBAM, transitions remain broad. This tunable behavior persists
for gels on nanostructured gold surfaces. Investigating PNIPAM-
co
-MBAM networks on gold plasmonic nanowell arrays is a
starting point for expanding their scope as thermo-controlled nanoactuators.
Surface-initiated
polymerization reactions are a powerful tool
to generate chain-end-tethered polymer brushes. This report presents
a synthetic strategy that gives access to structurally well-defined
hydrocarbon polymer brushes of controlled molecular weights, which
can be further modified to generate more complex surface-attached
polymer architectures. The hydrocarbon brushes reported in this study
are polymethylene brushes that are obtained via surface-initiated
C1 polyhomologation of dimethylsulfoxonium methylide. The strategy
outlined here is based on the use of an alkylboronic acid pinacol
ester initiator, which allows for controlled, unidirectional chain
growth by monomer insertion into only the C–B bond of the initiator
and which presents the polymerization active group at the growing
polymer chain end. This surface-initiated C1 polyhomologation methodology
is compatible with photopatterning strategies and can be used to generate
micropatterned polymethylene brush films. Furthermore, conversion
of the boronic ester chain-end functionalities to hydroxyl groups
allows for selective chain-end modification and enables access to
a variety of surface-anchored block copolymer architectures by chain
extension via, for example, ring-opening or atom transfer radical
polymerization chemistries.
Verschiedene Polyimide und Polyamide wurden in letzter Zeit durch hydrothermale Synthese in nichts als H2O unter Hochdruck‐ und Hochtemperaturbedingungen hergestellt. Keines dieser Polymere weist jedoch ein konjugiertes Polymerrückgrat auf. Hiermit berichten wir über eine Erweiterung des synthetischen Anwendungsbereichs dieser einfachen und von Natur aus umweltfreundlichen Polymerisationstechnik auf die Herstellung von konjugierten Polymeren. Ausgewählte Vertreter von zwei verschiedenen Polymerklassen, Pyrronpolymere und Polybenzimidazole, wurden hydrothermal synthetisiert. Neben einer mechanistischen Diskussion der Polymerbildung wird auch eine elektrochemische Charakterisierung des vielversprechendsten Produktes präsentiert.
A change of perspective can allow for surprising views. Water becomes a potent medium for synthesizing highly aromatic compounds when heated to high temperatures. In their Research Article on page 15050, M. M. Unterlass and co‐workers report the hydrothermal synthesis of two classes of highly conjugated organic polymers, polybenzimidazoles and pyrrone polymers. The cover picture shows an abstraction of a water surface, which looks different from different angles and distances to the image, illustrating that liquid high‐temperature water becomes a powerful medium for transformations that would be inconceivable in room‐temperature water.
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