Influence of a polymeric gel on the in situ electropolymerization of 3,4-ethylenedioxythiophene and application in irreversible electrochemical indicators

Electropolymerization triggered inside of a pre-assembled device can produce a high-contrast, visually irreversible color change. This format of electrochemical indicator has potential applications in a broad range of commercial sectors, including authenticity labeling, healthcare, food packaging, and logistics. However, there is limited work exploring how polymer gel electrolytes, which are commonly employed in flexible electrochemical devices, influence the electropolymerization process. Here, we study the electrochemical polymerization of 3–4-ethylenedioxythiphene (EDOT) in a UV-curable ethylene oxide-propylene oxide-allyl glycidyl ether (EO-PO-AGE) polymer gel electrolyte. Using potential step methods and cyclic voltammetry, we find that the addition of the polymer gel matrix lowers the overpotential required for film formation by 0.1 V compared to the liquid electrolyte. Furthermore, indicators with the polymer gel electrolyte show an increase in coloration efficiency, and greater visual homogeneity compared to indicators with the liquid electrolyte. Graphical Abstract