Final Report for Grant "Direct Writing via Novel Aromatic Ladder Polymer Precursors" Page: 2 of 17
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optical microscopy writing, 4 photopatterning of diacetylenes,15 patterned luminescent
polymers,16'17 creation of micro electromechanical (MEMS) structures of glassy carbon,18, 19 and
fabrication of electrochemically modulated optical diffraction gratings.20 These reports did not
focus on achieving high contrast in the relative electrical conductivity between exposed and
unexposed material, however. Photoinduced doping and photolithographic patterning of
poly(methyl aniline) produced patterns with a conductivity of 10-3 S/cm, but only after HCl
exposure. Poly(thiophene) derivatives have been patterned photolithographically but require
subsequent wet-etching to define the pattern of the polymer.22-24 Poly(butadiene) films have
been simultaneously isomerized and iodine doped to form conducting patterns with a
conductivity of ca. 10-5 S/cm.25 Selective laser irradiation of BBL produced conducting lines of
this material at relatively large length scales. 26 Such demonstrations, while illustrative, do not
meet the criteria set for a successful direct writing of polymer-based electrical connects or
circuitry, particularly if it is desired to write at the nanometer scale.
Several routes to synthesize graphitic material or aromatic ladders27-29 exist. However,
none appear adequate for the conversion of the material to a conductive form that satisfies the
following criteria. Each of these issues would defeat attempts to form micrometer-scale to
nanometer-scale patterns of conducting material by direct writing (Figure 1).
0 The precursor polymer is straightforward to synthesize - minimal chemical synthesis of
the monomer units is required.
0 The precursor polymer can form durable films so that it is applicable to the preparation of
devices and carbon circuitry. In some cases, the precursor is not very soluble and requires strong
acids to process it. In other cases, the precursor does not form mechanically stable films.
O The synthetic route is amenable to the installation of chemical functionalities so that
binding/transduction elements can be introduced for sensor applications and the photophysical
and electronic properties of these polymers can be tuned.
O The final polymer displays high electrical conductivity.
O The conversion of the precursor takes place under mild heating or photochemical
conversion - e.g. no chemical reagents are required that cannot operate in the solid state. This
criterion is typically the one that current materials are least able to meet. Often, the conversion
of the precursor polymer requires high temperatures. When chemical reagents are employed in
the conversion, they are typically harsh and likely produce additional, degradative reactions on
the polymer chain.
O It is possible to characterize the final polymer reasonably well.
Our approach to new precursor polymers for direct writing is shown in Scheme I below.
This route involves cyclization of benzylic nitriles - as we show below on model oligomers,
aromatization takes place via tautomerization. This route meets all of the criteria for direct
writing elucidated above.
Gorman/NCSU, "Direct Writing via Novel Aromatic Ladder Polymer Precursors"Page 2 of 17
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Gorman, C. B. Final Report for Grant "Direct Writing via Novel Aromatic Ladder Polymer Precursors", report, October 29, 2010; United States. (https://digital.library.unt.edu/ark:/67531/metadc1013850/m1/2/: accessed March 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.