Direct Photopatterning of Electrochromic Polymers

• Published in: Advanced functional materials 2013-08, Vol.23 (30), p.3728-3737
• Main Authors: Jensen, Jacob, Dyer, Aubrey L., Shen, D. Eric, Krebs, Frederik C., Reynolds, John R.
• Format: Article
• Language: English
• Subjects: Crosslinking; Electroactivity; electrochromic polymers; Electrochromism; Patterning; photopatterning; Polymerization; Polymers; solution processable; Solvents; Thin films
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201203005

Propylenedioxythiophene (ProDOT) polymers are synthesized using an oxidative polymerization route that results in methacrylate substituted poly(ProDOTs) having a Mn of 10–20 kDa wherein the methacrylate functionality constitutes from 6 to 60% of the total monomer units. Solutions of these polymers show excellent film forming abilities, with thin films prepared using both spray‐casting and spin‐coating. These polymers are demonstrated to crosslink upon UV irradiation at 350 nm, in the presence of an appropriate photoinitiator, to render the films insoluble to common organic solvents. Electrochemical, spectroelectrochemical, and colorimetric analyses of the crosslinked polymer films are performed to establish that they retain the same electrochromic qualities as the parent polymers with no detriment to the observed properties. To demonstrate applicability for multi‐film processing and patterning, photolithographic patterning is shown, as is desired for fully solution processed and patterned devices. Direct photopatterning of a conjugated electroactive dioxythiophene‐based polymer is presented. Thin films of the polymer are spray‐cast from organic solvents, followed by insolubilization via photocrosslinking. The crosslinking process does not cause any detriment to the electroactivity or optical properties of the polymer, which can be redox switched between a colored and bleached state, as desired for electrochromic displays and windows.