Preventing HO-TriggeredCovalent Cross-Linking Enables All-Aqueous Processable and RecoverableFunctionalized Polythiophene-Based Cellulose Coatings

Journal article, 2026

The transition to sustainable electronics requires electroactive materials that are processable in green solvents, operationally stable, and recyclable or recoverable at their end of life. This work explores recoverable electroactive cellulose coatings using a carboxylate-functionalized polar polythiophene (PCAT-K). PCAT-K is water-processable and can be reversibly fixated onto cellulose threads by modulation of the secondary interactions via acid-base chemistry, showing promise for circular material use. To obtain electrically conducting PCAT-K-cellulose threads, acid-mediated oxygen doping of the PCAT-K with p-toluenesulfonic acid was explored but led to undesired covalent cross-linking and loss of solubility and recoverability. Through spectroscopic and electrochemical analyses, it is shown that the covalent cross-linking originates from hydrogen peroxide generation during the doping process, which further reacts with PCAT to form hydroxyl radicals. To suppress radical formation, potassium iodide is introduced as a benign additive that catalytically decomposes hydrogen peroxide, preventing covalent cross-linking while maintaining electrical conductivity and recoverability. While the additive can negatively affect cellulose substrates at long doping times, this strategy allows for stable, conductive, and removable electroactive coatings on cellulose threads using water as the sole solvent. This study highlights a more reliable synthetic route to the water-processable conjugated polymer PCAT-K and suggests a mechanistic origin of acid-mediated oxygen doping-induced covalent cross-linking with a practical strategy to overcome it.