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May 2009: Weder, C.; Polymers React to Stress; News
and Views Article; Nature 2009, 459, 45.
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The latest polymers
are chameleon-like: they change color on deformation.
The mechano-chemical transduction mechanism underpinning
this effect could be used to make polymers that respond
in many other ways to mechanical stress. Our News and
Views piece on this subject was published in Nature.
For more information
click here. |
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May 2009: Kunzelman, J.; Gupta, M.; Crenshaw, B.R.;
Schiraldi, D.A.; Weder, C.; Pressure-Sensitive Chromogenic
Polyesters;
Macromol. Mater. Eng. 2009, 294, 244-249.
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Upon
self-assembly, certain oligo(phenylene vinylene)
chromophores exhibit pronounced changes of their optical
absorption and/or fluorescence properties. The covalent
integration of these dyes into the backbone of
polyesters creates new chromogenic pressure-sensitive
materials. The work, a collaboration with
Prof.
David Schiraldi’s group, was selected for the cover
of the journal. A
US patent that broadly covers this technology has
been issued to Case Western Reserve University.
For more information
click here. |
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March 2009: Tang, L.; Whalen, J.; Schutte, G.; Weder,
C.; Stimuli-Responsive Epoxy Coatings;
Appl. Mat. Interf. 2009, 1, 688-696.
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New
stimuli-responsive epoxy coatings with built-in chemical
and threshold temperature sensors were developed.
The design approach involves incorporating excimer-forming,
photoluminescent chromophores into the resin. Color
changes resulting from self-assembly or dispersion of
dye molecules allow one to monitor exposure of the
materials to undesirable external stimuli. A
US patent that broadly covers this technology has
been issued to Case Western Reserve University.
For more information
click here. |

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February 2009: Capadona, J.R; Shanmuganathan K.;
Trittschuh, S.; Seidel, S.; Rowan, S.J.; Weder, C.; Polymer
Nanocomposites with Microcrystalline Cellulose;
Biomacromolecules 2009, 10, 712–716.
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The ability to produce polymer nanocomposites, which
comprise a percolating, three-dimensional network of
well-individualized nanofibers, is important to maximize
the reinforcing effect if the nanofibers. Through the
utilization of a template–approach, nanocomposites based
on an ethylene oxide/epichlorohydrin copolymer and
nanofibers isolated from microcrystalline cellulose were
produced which display the maximum mechanical
reinforcement predicted by the percolation model. For more information
click here. |
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July 2008: K. D. Singer, J. Lott, T. Kazmierczak, H.
Song, Y. Wu, J. Andrews, E. Baer, A. Hiltner, C. Weder;
Melt-processed all-polymer distributed Bragg reflector
laser;
Optics Express 2008, 16, 10358-10363.
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Fabricating lasers using polymeric gain media and
resonators is attractive due to the relative ease of
processing polymers compared to inorganic
semiconductors, but manufacturing the microstructures
needed has been challenging. In collaboration with Ken
Singer’s group of CWRU’s Physics Department and the
group of Profs. Eric Baer and Anne Hiltner, we
fabricated a surface-emitting distributed Bragg
reflector (DBR) laser that has a compression moulded
gain medium and a co-extruded resonator. The approach
could allow mass production of polymer lasers by rapid
roll-to-roll methods. |
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September 2008: Mendez, J.D.; Weder, C.;
Cross-Linking Increases the Electrical Conductivity of
Poly(3,4-ethylenedioxythiophene);
Macromol. Chem. Phys. 2008, Early View DOI:
10.1002/macp.200800317.
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Increased Electrical Conductivity in
Poly(3,4-ethylenedioxythiophene) upon Cross-Linking:
The electrical conductivity of
poly(3,4-ethylenedioxythiophene) (PEDOT) films can be
significantly increased by the incorporation of small
amounts of conjugated cross-linkers. Optimized materials
display a conductivity of ~800 S/cm; this corresponds to
an increase of 36% compared to linear PEDOT. The paper
was published as part of Macromolecular Chemistry and
Physics series on New Frontiers in Functional
Polymers. For more information
click here. |
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July 2008: K. D. Singer, J. Lott, T. Kazmierczak, H.
Song, Y. Wu, J. Andrews, E. Baer, A. Hiltner, C. Weder;
Melt-processed all-polymer distributed Bragg reflector
laser;
Optics Express 2008, 16, 10358-10363.
|
Fabricating lasers using polymeric gain media and
resonators is attractive due to the relative ease of
processing polymers compared to inorganic
semiconductors, but manufacturing the microstructures
needed has been challenging. In collaboration with Ken
Singer’s group of CWRU’s Physics Department and the
group of Profs. Eric Baer and Anne Hiltner, we
fabricated a surface-emitting distributed Bragg
reflector (DBR) laser that has a compression moulded
gain medium and a co-extruded resonator. The approach
could allow mass production of polymer lasers by rapid
roll-to-roll methods. |
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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.
Sea cucumbers have the ability to rapidly alter the stiffness of their dermis. The modulus of this tissue is controlled by regulating the interactions among collagen fibrils, which reinforce a low-modulus matrix. We
developed a family of polymer nanocomposites, which mimic this architecture and display similar chemoresponsive mechanic adaptability. Materials based on a rubbery host polymer and rigid cellulose nanofibers exhibit a reversible
tensile modulus reduction from 800 to 20 MPa upon exposure
to a chemical regulator that mediates nanofiber
interactions. Using a host polymer with a thermal transition in the regime of interest, we demonstrated even larger modulus changes (4200 to 1.6 MPa) upon exposure to emulated physiological conditions.
Our current focus is the development of “smart” cortical
implants based on the new materials. 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. 2008,
47, 448-450. Invited Highlight.
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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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