Dr Michael B. Ramey
Assistant Professor of Chemistry
Appalachian State University
CAP 451, 262-2760, rameymb@appstate.edu
Dr. Ramey teaches a variety of organic chemistry classes at Appalachian State
University. He holds a Ph.D. in organic chemistry from the University of Florida under
the guidance of Dr. John Reynolds. His research involved the synthesis and
characterization of water-soluble conjugated polymers for light emission applications.
Prior to his work at UF, Dr. Ramey attended Virginia Polytechnic and State University
where he worked with Dr. Judy Riffle on high temperature polymers. Following graduate
studies, he worked as a researcher for the Air Force Research Laboratories at WrightPatterson AFB, Dayton, Ohio, until his appointment at Appalachian in August 2002.
Currently, research in the Ramey group centers around the use of organic
synthetic techniques to construct molecules for light emission and the assembly of
charged species for ionic conduction. The materials developed have potential
applications in the fields of photovoltaics, light emitting diodes (LED’s), and fuel
cell/battery membranes. Two specific projects are outlined below:
PROJECT TITLE A:
“Water-Soluble Conjugated Polymers for Use in Stimuli Induced Color Change
Detection Applications”
Conjugated, conductive polymers are on the forefront of revolutionizing the
display (LED) industry by capitalizing on their intense light emission/absorption
(“chromic”) properties (see Figure 1).1 The initial discoverers of “metallic-like” plastics
were recently awarded the Nobel Prize in Chemistry in 2000.2 These light weight, low
energy consuming, processible materials are challenging the state-of-the-art inorganic
materials for future supremacy in the light emitting device industry. A exciting avenue of
research in this area is to tailor the chromic responses while adding the beneficial
property of water-solubility. The addition of water-solubility to these materials will open
up new avenues in both the processing of such materials (i.e. more appealing to large
scale industrial processing where water can be used as the solvent) and make them ideal
candidates for use as sensors for biologically active molecules of interest. Appropriately
designed water-soluble conjugated polymers display remarkable color or conductivity
changes when exposed to different analytes such as metal ions, drugs, or DNA even at
minute levels.
The foundation of this project will begin with the synthesis of a variety of new
substituted 3,4-ethylenedioxythiophene (EDOT-R) molecules which will serve as base
units (monomers) to be coupled together to form polymers.3 Substitution will include the
incorporation of sulfonic acid, carboxylic acid, and ammonium salt groups into the
monomer which are known to impart water solubility into resulting polymer structures.
1
Handbook of Conducting Polymers, 2nd ed.; Skotheim, T.A., Elsenbaumer, R.L., Reynolds, J.R., Eds.;
Marcel Dekker: New York, 1998.
2
See website “The Nobel Prize Internet Archive”: http://www.almaz.com/nobel/ .
3
Groenedaal, l.; Jonas, F.; Freitag, D.; Pielartzik, H.; Reynolds, J.R. Adv. Mater.2000, 369, 87.
Figure 1. Illustrative example of the color (“chromic”) changes available from a single conjugated
polymer (left –absorption4, right-fluorescence). The changes can be triggered via a change in applied
voltage or exposure to a particular analyte. Keep in mind these amazing materials are not too different from
the common plastics of everyday use, yet can conduct electricity and emit light.
After a group of these molecules is constructed, each will be exposed to a variety
of polymerization techniques in order to determine which methodology is best to enact
the conversion to high molecular weight. (see Figure 2).
Figure 2
O
Polymerization Techniques
S
O
electrochemical
S
S
O
O
x
numerous chemical
O
R
O
R
long chain of connected
EDOT monomers
EDOT-R
R
O
R=
S
PolyEDOT-R
OH
R
sulfonic acid
O
O
carboxylic acid
OH
ClN
4
H
ammonium salt
Taken with permission from website “Dr. Reynolds Page”: http://www.chem.ufl.edu/reynolds.html .
After reaching the polymer stage, these materials will be rigorously analyzed
using cyclic voltammetry (electron movement properties), Ultraviolet-Visible and
Fluorescent Spectroscopy (light absorption and emission properties), and gel-permeation
chromatography (molecular weight determination) all of which are available within the
ASU Chemistry Department. Evaluation of the project will be measured via two
components: 1) successful synthesis of new materials and 2) the electronic and light
absorption/emission responses of the polymers when exposed to different stimuli.
Assuming strong initial research results, the knowledge gained would provide evidence
to help garner additional funding from other non-ASU sources and allow expansion into
more sophisticated testing, such as DNA or water-contaminate detection.
PROJECT TITLE B:
“Polyelectrolytes for Ionic Conduction in Fuel Cells and Rechargeable Batteries”
Currently, there is great interest in cost effective and efficient fuel cells. 5,6 Proton
exchange membranes (PEMs) are essential to the operation and advancement of fuel cell
technology.7,8 Sulfonated polymers / solid polyelectrolytes lead the frontier in PEMs. the
current state of the art membrane, Nafion® produced by DuPont, is an expensive
sulfonated fluorocopolymer with operating temperature limitations. Numerous examples
in the current literature are present that outline investigations into materials that attempt
to avoid the limitations of the current membranes.9, 10, 11, 12 Table I lists a set of standard
properties necessary for a new material to be considered a good candidate for use as a
PEM.
Table 1: Evaluation Criteria for Prototype PEMs
Parameter
Ionic Conductivity
> 100 mS/cm
Criteria
Electrical Conductivity
>10 M
Dimensional Stability
H2O2 peroxide stability
Chemical Stability
Lifetime Analysis
<10 % change @ 100°C (based upon original dimension)
>2 hours vs. NIST standard
Resistant to oxidation and hydrolysis
100 hour life test @ 500 mA/cm2
McGrath, J.E.; Formato, R.; Harrison, W.; Mecham, J. “Sulfonated Poly(arylene ether sulfone)s as
Potential PEMs”, ACS Symposium March 1999.
6
Jacoby, M. “Fuel Cells for Heading for Sale”, Chemical and Engineering News, 77, 1999.
7
Zhang, Y.; Litt, M.; Savinell, R.; Wainright, J. “Molecular Design Considerations in the Synthesis of
High Conductivity PEMs for Fuel Cells:, Polymer Preprints, 40(2), 1999.
8
Wasmus, S.; Kuver, A. J. Electroanaytical Chem., 461, 1999.
9
Faure, S.; Gebel, G.; Mercier, R.; Pineri, M., Sillion, B.; Proceeding of the Second International
Symposium on New Material Fuel Cell Systems, Savadogo, O.;Roberge, P. Eds. 24(10), 1997.
10
Wang, F.; Ji, Q.; Harrison, W.; Mecham, J.; Formato, R.; Kovar, R.; Osenar, P.; McGrath, J. “Synthesis
of Sulfonated Poly(Arylene Ether Sulfone)s via Direct Polymerization”, Polymer Preprints, 41(1), 237,
2000.
11
Gunduz, N.; McGrath, J. “Synthesis and Charaterizaiton of Sulfonated Polyimides”, Polymer Preprints,
41(1), 183, 2000.
12
Shobha, H.; Smalley, G.; Sankarapandian, M.; McGrath, J. “Synthesis and Characterizaiton of
Sulfonated Poly(Arylene Ether)s Based on Functionalized Triphenyl Phosphine Oxide for Proton Exchange
Membranes:, Polymer Preprints, 41(1), 180, 2000.
5
The focus of this project is synthesize a variety of multi-armed, polyelectrolytic
hexaphenylbenzenes, capable of conducting a myriad of charged species. These
materials provide 6 charged units per molecule, thus maximizing the potential
conductivity of a single unit. Additionally, the central benzene rings are twisted out of
plane in the “real” molecule, thereby improving the processing and solubility properties
of the materials. This is essential for blending these materials into film forming polymers
which will serve as the membrane material in a fuel cell. Previous research has shown
such hexaphenylbenzenes to be thermally stable and resistant to harsh environmental
conditions.13 Examples are given below:
X-
I
+
M- O
N
II
H
O
O
O
O
+
M -O
-
X
O- M +
N
+
M -O
N
O
O
O-M+
Where M+ is Li+ , K+, Na+, or H+
O
O
O
H
O- M +
O
O
H
X-
H
N
N
H
X-
XO
H
N
X-
Where X- is Cl- , Br-, F- , etc.
For fuel cell applications, molecule I with M+ = H+ (proton) will be investigated.
One can picture an array of these molecules positioned within a polymer matrix capable
of passing an H+ (proton) from molecule to molecule thereby providing the necessary
proton conduction. A similar mechanism would exist when M+ = Li+, allowing for the
transport of lithium ions within a matrix. This type of conduction is crucial for
rechargeable lithium ion batteries. Molecule II with a variety of negatively charged
counterions would be an excellent candidate for use in applications ranging from water
softening to household cosmetic applications.
(a) Frechtenkotter, Andreas; Mullen, Klaus; Watson, Mark D. “Big is Beautiful—“Aromaticity”
Revisited from the Viewpoint of Macromolecular and Supramolecular Benzene Chemistry.” Chem. Rev.,
2001, 101, 1267-1300. (b) Fechtenkotter, Natalia Tchebotareva; Mullen, Klaus; Watson, Mark. “Discotic
Liquid Crystalline Hexabenzocoronenes Carrying Chiral and Racemic Branched Alkyl Chains:
Supramolecular Engineering and Improve Synthetic Methods.” Tetrahedron, 2001, 57, 3769-3783. (c)
Morgenroth, Frank; Mullen, Klaus. “Dendritic and Hyperbranched Polyphenylenes via a simple DielsAlder Route.” Tetrahedron, 1997, 53, 15359-15365.
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