Enhanced stretchability and robustness towards flexible ionotronics via double-network structure and ion-dipole interactions

Abstract

Ionic conductive gels enabled by ionic liquids (ionogels) are promising candidates for flexible electronics due to less concerns on liquid evaporation and leakage. However, it is still a challenge to simultaneously enhance the strength and stretchability for an ionogel. Here, we report a mechanically robust and stretchable ionogel, employing fluorinated acrylic monomers to construct double network (DN) structure and ion-dipole interactions between ionic liquid and the resulted polymer backbone. The highly transparent ionogels present excellent mechanical properties, with ultimate stretchability up to 784% and strength 5.6 MPa. Noticeably, the addition of ionic liquid up to 30% results in a substantial increase of stretchablity without sacrificing the ultimate stress, due to the strong ion-dipole interactions. With a good conductivity (10−4 to 10−5 S cm−1), the ionogels can be used as flexible conductors for electroluminescent devices and wearable strain sensors, both displaying excellent performance. This study provides a practical strategy on the fabrication of robust and stretchable ionogels for flexible ionotronics.