Flexible Conductive Polymer Patterns from Vapor Polymerizable and Photo-Cross-Linkable EDOT

We explored direct photopatterning of a vapor polymerizable and photo-cross-linkable 3,4-ethylenedioxythiopene (EDOT) to make it suitable for use in electronics applications. We prepared a conductive polymer, PEDOT-MA, using vapor phase polymerization (VPP) of the (2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methyl methacrylate (EDOT-MA) and photochemically induced a conductivity change of the PEDOT-MA film to ensure a flexible conductive pattern. The room-temperature conductivity (σRT) of the PEDOT-MA film on PET was 30−120 S/cm, depending on the oxidant layer thickness and was increased ∼30% when the PEDOT-MA film was doped with aqueous solution of p-toluenesulfonic acid. Photoreaction of PEDOT-MA decreased the σRT to 1.7 × 10−3 S/cm because of the photo-cross-linking of the side chain. The transparency of the conductive films was tuned using the vapor polymerization time to control the film thickness. The photo-cross-linking reaction of the side chain generated micropatterns having line widths of 50−0.9 μm, in which the light-exposed areas appeared as bleached and less conductive. A diffractive, flexible, conductive film with 41% of diffraction efficiency was obtained from the line-patterned film having a spacing of 0.9 μm.