Patterning of Conducting Polymers Using UV Lithography: The in-Situ Polymerization Approach

Abstract

We report on the in-situ polymerization of 3T with Cu(ClO4)2 inside several host polymers such as Novolak-based negative-tone photoresist, polystyrene (PS), poly(4-vinylphenol) (P4VP), poly(methyl methacrylate) (PMMA), and poly(4-vinylphenol)-co-(methyl methacrylate) (P4VP-co-MMA) to form an interpenetrating polymer network (IPN). Conducting IPN films in the order of 10–4–150 S/cm are obtained depending on the specific IPN composition. Moreover, the convenience of this synthetic approach has been demonstrated using a commercially available negative-tone photoresist based on Novolak as a host polymer. Novolak photoresist was properly formulated with 3T and Cu(ClO4)2 to preserve as far as possible the negative lithographic characteristics of Novolak-based photoresist and generate conductive micropatterns by means of UV lithography. The CP is in situ synthesized into the Novolak matrix by a postbake after the lithography process (exposure + development). The electrical conductivity of the patterned film is 10–2 S/cm. We accurately patterned three different types of microstructures with different resolutions: interdigitated structures with a width of 100 μm, 200 μm side squares, and a 20 μm wide cross. We believe this synthetic approach is of potential application to modify the conductivity of numerous insulating polymers while preserving their physical and chemical properties.

Surface Modification of Polymers: Methods and Applications

“…This method can also be used to modify the conductivity of numerous insulating polymers while preserving their physical and chemical properties 190. Abargues et al have reported photolithography process for polymerization of terthiophene (3T) with Cu(ClO 4 ) 2 inside several host polymers such as Novolak‐based negative‐tone photoresist, PS, poly(4‐vinylphenol) (P4VP), PMMA, and poly(4‐vinylphenol)‐ co ‐(methyl methacrylate) (P4VP‐ co ‐MMA) for developing interpenetrating polymer network (IPN) ( Figure a) . A spin‐coated UV‐patternable polymer containing 3T and Cu(ClO 4 ) 2 was exposed to UV light, baked, and developed.…”

“…a) Scheme of the fabrication of the conducting interpenetrating polymer network (IPN) patterns. Reproduced with permission . Copyright 2012, American Chemical Society.…”

Two‐Photon Nanolithography Enhances the Performance of an Ionic Liquid–Polymer Composite Sensor

“…Generally, photoresist is an electronic insulator in its pure (i.e., undoped) state. In order to significantly increase the conductivity of the polymerized material, other composites, such as terthiophene (3T) with copper (II) perchlorate, carbon black particles, silver or protonically doped polyaniline nanoparticles have to be added. However, these Electrically Conductive Polymer Composites (ECPCs) have several restrictions.…”

Novel ionic liquid - polymer composite and an approach for its patterning by conventional photolithography

“…The examples of conductive fillers are terthiophene (3T) with copper (II) perchlorate [7], silver nanoparticles [8], graphite [9] or carbon black particles [10], protonically doped polyaniline (PANI) nanoparticles [11], and others [12,13]. However, these materials have several limitations: (1) the addition of filler particles requires control of material viscosity by addition of various solvents, influencing the photo-polymerization process;…”

“…(3) the resolution is constrained to 10 -30 μm because of the light diffraction by filler particles [7,8,9]; (4) and finally, the cured material has low optical transparency over the visible range.…”