Self-Healing Starch-Based Ionogels with Hydroneutral Dipole-Dipole Interactions

Transparent ionically conductive self-healing polymeric materials are essential for enabling many next-generation technologies in areas including electronics and robotics. However, many of them lose their self-healing ability when they come into contact with water. Herein, starch-based, conductive, underwater-healable and transparent ionogels for soft electronics (SCUTE) are introduced. SCUTEs consist of starch macromolecules that are partially substituted with cyanoethyl groups, and incorporated with hydrophobic ionic liquid tributyl(methyl)ammonium dicyanamide. The aprotic cyanoethyl groups possess a high polarity, thereby capable of forming dipole-dipole interactions stronger than hydrogen bonding of hydroxyl groups. Despite its high polarity, the cyanoethyl groups possess hydroneutral characteristics that only interact weakly with water. This allows dipole-dipole interactions between cyanoethyl groups to be uninterrupted even in the presence of water. More importantly, the synergistic effect between the hydroneutural cyanoethyl dipole-dipole and hydrophilic hydrogen bond led to SCUTEs' distinct water-accelerated self-healing ability. In particular, healing efficiency in stretchability for SCUTE-20 increased from 37.4% in ambient to 92.0% when exposed to water, for a healing duration of 24 h. To show its potential in soft electronics, SCUTE is demonstrated as electronic skin for robotics control and 3D-printed aquatic electronics.