| Post Doctoral Fellow
Université du Québec
Institut national de la recherche scientifique
Énergie, Matériaux et Télécommunications
1650, boulevard Lionel-Boulet
Varennes, Québec, Canada
J3X 1S2
Telephone: +1 (450) 929-8181
Fax: +1 (450) 929-8102
duffin@emt.inrs.ca
www.emt.inrs.ca
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Conjugated polymers are fascinating materials which consist of chains
of repeated building blocks with alternating double and single carbon
bonds. Because of the delocalization of charge inherent in this bonding
arrangement, they possess unique electronic properties. However, these
materials need not be chains – we can easily imagine a scenario
where a tailored building block (monomer) is designed to polymerize in
two non-colinear directions, producing a conjugated sheet. Indeed, nature
already provides us with the simplest example of such a material, which
is graphite. Much is understood about conventional one-dimensional (1D)
polymers, yet the extension of the study of these materials into 2D beyond
simple graphitic structures has not yet been well explored. We know that
chain polymers (1D) can be grown as cross-linked meshes, or can be held
together by the presence of a templating surface or via hydrogen bonding.
Unfortunately, these structures are delicate and revert to disordered
solids over time. A true graphene-like 2D covalent mesh would be far more
robust. The challenge of creating purpose-designed 2D covalent sheet will
generate substantial fundamental interest in both electronic and material
branches of nanoscale research. Our collaboration with the synthetic chemistry
group of D.F. Perepichka allows us to select tailored monomers with favorable
bonding arrangements.
My current efforts towards this goal involve the attempted
growth of conjugated polymer sheets at the surfaces of noble metals. In
particular, we are attempting to catalyze the polymerization by exploiting
the nature of Ulmann dehalogenation using the substrate itself. We are
able to selectively grow polymers only upon the arrival of the monomers
at the surface, and hence their growth follows the geometry of the lattice.
We have already made significant strides in demonstrating conventional
1D growth using this technique on Cu(110), and hope to extend to two dimensions
in the coming months. Though we are not yet certain of the existence of
2D polymers, the dehalogenation reaction has proven an interesting method
for guiding chemical reactions at a surface, and will likely serve as
a useful method for further deposition studies.
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