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March 2008: Capadona, J.R; Shanmuganathan K.; Tyler,
D.; Rowan, S.J.; Weder, C.; Bio-inspired chemo-mechanical
polymer nanocomposites that mimic the sea cucumber dermis;
Science 2008, 319, 1370-1374.
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The paper published in one of the world’s most
prestigious scholarly scientific journals reports
ground-breaking work on a new type of polymer that
displays mechanic adaptability. Using the skin of
sea cucumbers as blueprint, we developed new polymer
nanocomposites, which can change their mechanical
properties on command. The new materials were designed
to respond to a chemical stimulus – exposure to water –
and are comprised of a low modulus polymer matrix into
which strong and rigid nanofibers are embedded so that
they form a network. In the absence of water, the
nanofibers are ‘glued’ to each other and the nanofiber
network dominates the mechanical properties of the
material. In this state, the material is strong and
rigid. If the material is exposed to water, it swells
very slightly. The water molecules ‘unglue’ the
nanofibers and the material becomes about 1000 times
softer. Its properties now resemble those of a rubber.
The new materials may be useful for a range of
applications. Our current focus is the development of
“smart” cortical implants. Microelectrodes based on the
new polymers are stiff when implanted, but then turn
flexible. This adaptability may have significant
clinical advantages. The project is a collaboration with
the groups of Profs.
Stuart Rowan,
Dustin Tyler, and
Dr. Jeff Capadona is
part of the
Advanced Platform Technology (APT) Center at the Louis Stokes Cleveland VA Medical Center,
For more information
click here.
To read a news story on the work
click here.
Download this article from our
publications page.
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February 2008: Kunzelman, J.; Chung, C.; Mather, T.M.;
Weder, C.; Shape Memory Polymers with Built-In Threshold
Temperature Sensors; J. Mater. Chem. 2008,
18, 1082 - 1086.
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New
shape memory polymers with built-in temperature sensors
were developed by integrating excimer-forming
fluorescent chromophores into a cross-linked
poly(cyclooctene) matrix. Color changes resulting from
self-assembly or dispersion of dye molecules allow one
to monitor reaching of the set/release temperature of
the materials. The work,
a
collaboration with
Prof.
Pat Mather’s group at Syracuse University,
was selected for the back cover of the journal and
highlighted as a hot paper. A
US patent that broadly covers this technology has
been issued to Case Western Reserve University.
For more information
click here.
For a link to JMCs hot papers
click here.
To read a news story on the work
click here.
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December 2007: Capadona, J.R; van den Berg, O.;
Capadona, L.; Tyler, D.; Rowan, S.J.; Weder, C.; A versatile
approach for the processing of polymer nanocomposites with
selfassembled nanofibre templates; Nature Nanotechnology
2007, 2, 765-769.
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The incorporation of nanoparticles into polymers is a
design approach that is employed in all areas of
materials science. The concept is attractive since it
enables the creation of materials with new or improved
properties by mixing multiple constituents and
exploiting synergistic effects. The broad technological
exploitation of polymer nanocomposites is, however,
stifled by the lack of effective methods to control
nanoparticle dispersion. Our latest paper reports a
simple and versatile process for the formation of
homogeneous polymer/nanofiber composites. The approach
is based on the formation of a three-dimensional
template of well-individualized nanofibers, which is
filled with any polymer of choice. We demonstrate that
this template approach is broadly applicable and allows
for the fabrication of otherwise inaccessible nanocomposites of immiscible components.
For more information
click here.
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December 2007: Weder, C.; Hole Control in Microporous
Polymers; Angew. Chem. Int. Ed. 2007 Invited
Highlight,
Early View (DOI 10.1002/anie.200704697).
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Microporous materials with large specific surface
area and pore sizes of molecular dimensions are of
interest due to their use in applications that range
from selective membranes to molecular sieves to
catalysts to photonic crystals. Organic polymers would
represent a desirable alternative to inorganic porous
materials, since they combine low density with good
mechanical properties and ease of processing. However,
until recently it was impossible to gain control over
their porosity, especially the pore sizes. Several
approaches have emerged to solve this problem. Chris
Weder’s article in Angewandte Chemie highlights work by
Andy
Cooper et al., who reported that control over pore
size can be achieved in amorphous
conjugated
poly(arylene ethynylene) networks. |
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October 2007: Islangulov, R.R.; Lott, J.; Weder, C.;
Castellano, F.N.; Noncoherent Low-Power Upconversion in
Solid Polymer Films;
J. Am. Chem. Soc. 2007,
129, 12652-12653.
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Noncoherent low-power photon upconversion has been
realized in solid thin films composed of an
ethyleneoxide/epichlorohydrin copolymer doped with
palladium octaethylporphyrin (PdOEP) and
9,10-diphenylanthracene (DPA). Selective excitation of
PdOEP at 544 nm generates easily visualized DPA
fluorescence in the blue with noncoherent light sources
under ambient laboratory conditions. The work, published in the Journal of
the American Chemical Society, is a collaboration with
Felix N. Castellano's group at Bowling Green State
University. |
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August 2007: Kunzelman, J.; Crenshaw, B.R.; Weder,
C.; Self-Assembly of Chromogenic Dyes - A New Mechanism for
Humidity Sensors;
J. Mater. Chem. 2007, 17,
2989-2991.
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Upon
self-assembly, certain photoluminescent chromophores exhibit pronounced changes of their
optical absorption properties. The
integration of these dyes into a polymer matrix
allows facile monitoring of external stimuli,
for example mechanical stress, temperature
history, or - as shown in this new paper
published in the Journal of Materials Chemistry - exposure to
moisture. The work was selected for the cover of
the august issue of the journal. A
US patent
that broadly covers this technology has just
been issued to Case Western Reserve University.
For more information
click here.
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