A stretchable, environmentally stable, and mechanically robust nanocomposite polyurethane organohydrogel with anti-freezing, anti-dehydration, and electromagnetic shielding properties for strain sensors and magnetic actuators

Abstract

Herein, a novel magnetic-responsive, stretchable, and conductive organohydrogel with anti-freezing, anti-dehydration, and electromagnetic shielding abilities was well prepared. First, Fe₃O₄ nanoparticles were functionalized with tannic acid (TA) to obtain Fe₃O₄@TA nanoparticles, which were then incorporated into a polyurethane matrix comprising a phenol–carbamate network and hydrophilic polyethylene glycol (PEG) via in situ polymerization to obtain magnetic polyurethane nanocomposites. Subsequently, the conductive polyaniline was further introduced into the nanocomposite hydrogel through in situ polymerization triggered by ammonium persulfate (APS) after soaking the nanocomposite film in a mixed solution containing aniline and the dopant phytic acid. Finally, the nanocomposite hydrogel was further soaked in the glycerol and CaCl₂ aqueous solution to obtain the organohydrogel, which exhibited good mechanical properties (0.83 MPa of tensile strength and 371% of elongation at break), conductivity (0.36 mS cm⁻¹), freezing tolerance (−20 °C), and long-term anti-dehydration stability (almost 90% weight retention at room temperature). Benefiting from the good conductivity and magnetic response, the prepared organohydrogel can be used as a strain sensor to monitor human activities in real time and can also be used as a magnetic responsive switch to control the “ON/OFF” state of the bulb. In addition, the target organohydrogel exhibited much improved electromagnetic shielding effectiveness due to the incorporation of Fe₃O₄@TA nanoparticles. Impressively, by virtue of the dynamic phenol–carbamate network constructed by TA and NCO-terminated polyurethane chains, polyaniline and Fe₃O₄@TA particles could be recovered from the organohydrogel matrix. This well-designed multifunctional organohydrogel has great application potential in deformable wearable devices, magnetic actuators, and electromagnetic shielding devices.