Dicationic Ionic Liquids as Antibacterial and Conductive Plasticizers: Effect of Cationic Structures on Starch Film Properties for Flexible Electronics

In the flexible electronics field, the growing issue of electronic waste and the massive use of nonbiodegradable substrates have led research toward sustainable materials based on natural polymers such as starch. Nevertheless, it lacks the specific properties of a processable plastic material and has no appreciable conductivity. Therefore, the use of appropriate plasticizers is necessary. Dicationic ionic liquids (DILs), characterized by good conductivity and lower toxicity compared with monocationic ILs, may represent a valid suggestion. In addition, DILs show greater antibacterial efficacy, which is particularly suitable for the production of wearable devices. This work investigates the role of the cationic structure of DILs in the characteristics of flexible starch films with both conductive and antibacterial properties. Four 1-ethyl-3-methyl imidazolium-based DILs with varying chain linkers were used to prepare starch films via solution casting. The study examined the impact of these plasticizers on the films' mechanical properties, thermal stability, wettability, electrical conductivity, and antimicrobial activity. The prepared films were tested as materials for making wearable strain sensors, suggesting potential applications in the field of flexible electronics.