3D Printable Supramolecular Viologen-Cationic Polyurethane Ionotronics for Multimodal Sensing and Displays

Ionic polyurethanes with excellent properties have garnered significant attention in flexible wearables. However, it is still challenging to achieve ionic polyurethane ionotronics with both excellent mechanical properties and functionalization. Here, a series of hydroxypropyl viologen (HDPV) cationic-based supramolecular polyurethane with tunable strength (7.6-76.6 MPa), toughness (29.1-285.3 MJ m^-3), and elongation (499.8%-1102.3%) are developed by balancing HDPV cations and dynamic sextuple hydrogen bonds into the polyurethane. Dynamic modulation of the mechanical and electrochromic properties of the polyurethane can be achieved by adjusting the content of HDPV cations and dynamic sextuple bonds. Strong electrostatic interactions between the HDPV cationic-based polyurethane and the ionic liquid resulted in the preparation of ionogels with excellent pressure/strain and temperature sensing properties. Additionally, benefiting from the redox properties of the polycationic backbone, electrochromic devices fabricated from HDPV cationic-based polyurethane demonstrated a high modulation range of 79.1%, a certain degree of color memory effect, and excellent cycling stability. Shape customization of flexible electrochromic devices of HDPV cationic-based polyurethane can be achieved by 3D printing technology. The study paves a new avenue for the fabrication of flexible visual ionotronics with high stability and versatility.