Introducing a reversible linkage to block copolymer self-assembly: Towards controlling nanopore chemistry

Full text of DOI:10.2533/chimia.2012.444

444 CHIMIA 2012, 66, No. 6
Columns
doi:10.2533/chimia.2012.444
Polymer and Colloid Highlights
Division of Polymers and Colloids
A Division of the Swiss Chemical Society
Introducing a Reversible Linkage to Block Copolymer
Self-Assembly: Towards Controlling Nanopore
Chemistry
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NEt3/T
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C/D
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P,D
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85%
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Jingyi Rao, Swati De, and Anzar Khan*
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*Correspondence: Dr. A. Khan, Institut für Polymere, ETH Zürich,
CH-8093 Zürich, Tel.: +41 44 633 6474, E-mail: anzar.khan@mat.ethz.ch
sonication
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(10 min)
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Keywords: Block copolymer self-assembly · Dynamic covalent
chemistry · Nanoporous membranes
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Cu(I)Br,PMDETA
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Scheme 1.
membrane-functionalization were carried out both by re-
establishing imine bonds with fluorescent organic molecules and
via forming metal complexes.
Received: May 7, 2012
[1] F. S. Bates, G. H. Fredrickson, Annu. Rev. Phys. Chem. 1990, 41, 525.
[2] C. J. Hawker, T. P. Russell, MRS Bull. 2005, 30, 952.
[3] J. Rao, S. De, A. Khan, Chem. Commun. 2012, 48, 3427.
Fig. 1. Schematic representation of nanostructured thin film formation
from self-assembly of dynamic covalent diblock copolymer, subsequent
step of pore formation due to the reversibility of the copolymer linkage,
and tentative graphic representation of the functionalized-pore.
Block copolymer self-assembly[1] has shown remarkable
potential towards preparation of highly ordered nanoporous
membranes.[2] In this approach, covalently connected yet
chemically dissimilar polymer blocks phase separate into
ordered nanostructures with length scales on the order of
ten to a hundred nanometres. Selective removal of the minor
phase from these nanostructured polymer thin films affords
nanoporous membranes. Such membranes have found use in
surface patterning, templated nanomaterial synthesis, separation,
filtration, catalysis, sensing, and drug delivery applications.
The far-ranging applicability and performance of these porous
materials will further enhance if the surface of the nanopore
can carry chemically reactive functionalities that can be altered
under ambient conditions. So far, strategies for covalent chemical
functionalization of the nanopores in highly ordered porous
thin films remains undeveloped. To this end, we designed and
synthesized a diblock copolymer featuring incompatible blocks,
unsymmetrical block lengths, and a reversible copolymer linkage
(Fig. 1 and Scheme 1).[3] Self-assembly of this copolymer results
in nanostructured thin films exhibiting highly ordered cylindrical
morphology (Fig. 2). Removal of the nanosized cylinders by
reversing the dynamic covalent – oxy-imine – linkage then
affords ordered nanoporous membranes that contain chemically
reactive oxy-amine functionalities. Covalent and non-covalent
Fig 2. AFM height (a) and phase (b) images (1 µm × 1 µm) of the thin
film. Inset shows the corresponding Fourier transform. TEM (c, scale
bar = 100 nm) and SEM (d, scale bar = 300 nm) images of the thin film
after removal of the PEG cylinders.
If you are interested in submitting a new highlight, please contact:
Prof. A. Dieter Schlüter, Institut für Polymere, ETH Zürich
E-mail: dieter.schluter@mat.ethz.ch, Tel.: +41 44 633 63 80