Ultrastretchable Composite Organohydrogels with Dual Cross-Links Enabling Multimodal Sensing.

Building multiple cross-links or networks is a favorable way of diversifying applications of the hydrogels, which is also available for the organohydrogels prepared via the solvent replacement way. However, the situations become more complicated for organohydrogels due to the presence of replaced solvents. Therefore, the correlations between the multiple cross-links and final performance need to be better understood for the organohydrogels, which is vital for tailoring their inherent properties to expand final application scenarios. Polyacrylamide (PAM)/poly(vinyl alcohol) (PVA)/MXene composite organohydrogels with dual cross-links, namely, the covalently cross-linked PAM chains as the primary network and the physically cross-linked PVA/PAM chains with MXene particles as the secondary cross-links, were developed here for the study. The occurrence of the secondary cross-links plays multiple roles as sacrificial units endowing the system with ultrastretchability with an excellent strain-resistance effect and as temperature-sensitive units endowing the system with thermosensation ability with an outstanding temperature coefficient of resistance. Thus, the optimized sample can be used as a strain sensor with excellent environmental tolerance for detecting human motion as a pressure sensor to probe compression with weak deformation and as a thermal sensor to capture environmental temperature changes. This work provides valuable information on developing organohydrogels with superior performance for multimodal sensors.