Bulk versus surface-limited polymer encapsulation: A current pulse-induced approach for confined polymer coating selectively over quasi-oriented MXene aerogel

Polydimethylsiloxane (PDMS) encapsulation is a reliable technique to address the intrinsic poor mechanical stability of MXene-based aerogel frameworks. However, unavoidable bulk polymer within the pores of aerogel in the conventional crosslinking strategy excessively increases the weight of the resultant MXene-PDMS aerogel rendering sacrificed functionalities in lightweight applications. Here, we report a unique Joule heating-induced protocol for surface limited crosslinking of PDMS over the quasi-oriented 3D-MXene aerogel framework avoiding bulk polymer involvement, in which PDMS content can be tuned in a sub-second time scale via controlling the width and the magnitude of voltage pulses. The resultant robust, lightweight, hydrophobic, and highly flexible MXene-PDMS aerogel (JPM) is shown to be an excellent candidate for lightweight multifunctional applications, including electromagnetic interference (EMI) shielding, electro-thermal de-icing, and strain-sensing based human physiological activity monitoring. For example, the absolute EMI shielding effectiveness (SSE/t) of JPM is measured to be 17752 dB cm2/g, which is much higher than that obtained with conventional PDMS crosslinking. Thanks to the surface confined thin PDMS coating that offers very low hindrance to heat flow. As such, the generated heat in MXene during electro-thermal process can be rapidly transferred to the PDMS surface reaching > 200 °C within seconds at a lower applied voltage of 4 V, which finds application in fast de-icing with low input power. As-developed JPM based strain sensors can reliably monitor strain-induced deformations such as the human physiological movements and can also detect extremely weak vibrations like that of the human pulse rate.