Research Interests
Kinetics and mechanisms of free radical and ionic
polymerization; mechanical properties of polymers;
fluorocarbon chemistry; synthesis of novel monomers and
polymers; polymer electrical properties; liquid crystal
polymers; polyelectrolyte liquid crystals and their use as
fuel cell membranes.
Overview of Research
Kinetics and mechanisms of free radical and ionic
polymerization reactions have been explored, including
emulsion polymerization. Synthesis of a variety of novel
monomers and polymers with unique mechanical and transport
properties has been accomplished. Much work has been done on
poly(oxazolines) and their copolymers, studying surfactant
properties, photoelectric interactions, surface energies as
a function of structure, etc. Polymers containing carborane
siloxane repeat units were synthesized and their
extraordinary resistance to atomic oxygen was studied. When
the carborane unit oxidizes, it transforms into boric oxide
with a 60% weight gain which offsets the increase in density
when the glass is formed. New polybenzimidazole membranes
doped with H3PO4 were shown to be highly conductive. They
have been used as membranes in H2/O2 AND MeOH/02 fuel cells
under conditions where present membranes are inoperative. We
have developed novel barrier polymers that block O2 , N2,
etc. permeation as well as, or better than, any commercial
polymer. A new class of ethynyl terminated liquid crystal
monomers which polymerize to crosslinked liquid crystal
polymers has been made and studied. Because of their liquid
crystal organization, materials can be polymerized to high
conversion at temperatures more than 100° below the final
polymer Tg. Tg's over 400°C have been attained with very
high oxygen stability for the polymers. Various types of all
aromatic polymers, including double stranded ones, were made
and their electrical properties studied.
Current Activity
Work on solid polymer electrolytes resulted in the
development of benzimidazole polymers doped with phosphoric
acid as a new class of high temperature membranes. These
show great promise as Polymer Electrolyte Membranes in high
temperature fuel cells. The structure of NafionŽ was
re-evaluated, and its physical properties were interpreted
using a lamellar model, in contrast to the spherical domain
model in the literature. New work on solid polymer
electrolytes involves the synthesis and characterization of
liquid crystal, rigid rod polyimides containing sulfonic
acid groups. The structures are designed so as to increase
water retention and conductivity at low humidity. This has
been proved. X-ray characterization shows that the chain
separation in such structures is greater than in model
polymers. Conductivities at low relative humidity were
greater than NafionŽ by at least one order of magnitude and
increased rapidly with increasing temperature. This work has
now been extended to new poly(phenylene sulfonic acids)
which have shown great promise as candidates for
polyelectrolyte membranes that can function from below room
temperature to 200oC. Work has started on new non-water
extractable polyelectrolytes (not sulfonic acids) that can
replace phosphoric acid in the PBI membranes.
At present we are working on the following problems:
1. Synthesis of dendritic polyelectrolytes for fuel cell
membranes.
2. Membranes for micro and mini fuel cells.
3. Poly phenylene sulfonic acids as polyelectrolyte
membranes for fuel cells.
4. Novel non-water-extractable electrolytes to replace
phosphoric acid in membranes.
5. Hexagonal polymeric oligomers for use as templates in
various applications.
Recent
Publications
“Hydrolytic Stability of Sulfonic Acid-containing Polyimides
for Fuel Cell Membranes,” H.J. Kim, M.H. Litt, E.M. Shin,
et. al., Macromolecular Research, 12(6),
545-52 (2004).
Awards
Fellow of AAAS, Physical Society Advisory Board Member: I &
EC, Product & Development, J. Polymer Science
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