"Frozen" Ionogels with High and Tunable Toughness for Soft Electronics.

Abstract

As a promising material, ionogels have garnered increasing interest in various applications including flexible electronics and energy storage. However, most existing ionogels suffer from poor mechanical properties. Herein, an effective and universal strategy is reported to toughen ionogels by freezing the polymer network via network design. As a proof of concept, an ionogel is readily prepared by copolymerization of isobornyl acrylate (IBA) and ethoxyethoxyethyl acrylate (CBA) in the presence of ionic liquid, resulting in a bicontinuous phase-separated structure. The rigid, ionic liquid-free PIBA segments remain frozen at service temperature and serve as a load-bearing phase to toughen ionogels, while the flexible PCBA phases maintain high ionic liquid content. As a result, the mechanical properties of ionogels are noticeably improved, showing high rigidity (48.5 MPa), strength (4.19 MPa), and toughness (8.19 MJ · m^-3). Moreover, ionogels also exhibit remarkable thermo-softening performance, strong adhesiveness, high conductivity, shape memory properties, and satisfactory biocompatibility. When used as an ionic skin, the ionogel can not only respond to different deformation but also accurately and consistently detect body motions over long periods. This novel strategy in toughening ionogels can pave the way for the development of various tough and stable ionotronic devices.