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With the advent of the 5G era, hexagonal boron nitride (BN) platelets are ideal fillers to incorporate into polymers for preparing thermally conductive composites, which are applied in relieving the heat dissipation in electronic devices. In this study, we report a green, low cost, and high-efficient method to improve the thermal conductivity (λ) of carboxylated acrylonitrile-butadiene rubber (XNBR) composites via noncovalent modification of boron nitride (BN) via tannic acid (TA) chemistry. The noncovalent TA decorating on the surface of BN without deteriorating the surface structure of BN platelets ensures the high intrinsic λ of BN. Additionally, TA enhances the interfacial compatibility between the filler and matrix, as well as the formation of a thermally conductive path in the composites. The maximum throughplane λ is obtained by 30 vol % BN-TA-XNBR composite as 0.42 W/mK, which is 260% of that for pure XNBR (0.16 W/mK). The excellent dielectric properties of BN-TA-XNBR composites also indicates that the BN-TA-XNBR composites can meet the requirements of high capacitance and low energy loss of electronic devices. In brief, the TA chemistry provides potential applications in large scale production of thermally conductive composites in industries, as well as paves the way for advanced applications in nextgeneration miniaturization and integration of electronic devices.

Dielectric elastomer actuators (DEA) were widely applied in the field of sensors, artificial muscles, and microrobotics as they can convert electrical energy into mechanical energy. In this work, we have designed strawberry-like barium titanate/tannic acid-ferric ion/silver (denoted as BT/TA-FeIII/Ag) dielectric nanoparticles to improve the electromechanical performance of natural rubber (NR)-based composites. In the first instance, BT nanoparticles were modified by TA by introducing catechol- and pyrogallol-type phenols, which can be complexed with FeIII to form a coating of TA-FeIII on the surface of the BT nanoparticles (denoted as BT/TA-FeIII). Then, Ag nanoparticles were deposited on the surface of BT/TA-FeIII by the reduced Ag+ via an electroless plating method. The addition of BT/TA-FeIII/Ag nanoparticles in the NR matrix enhanced the electromechanical sensitivity of NR-based composites and thus increased the actuation strain of NR-based composites. In addition, the discontinuous silver layer deposited on the surface of BT/TA-FeIII/Ag nanoparticles maintained good insulation of NR-based composites. In the final step, a high actuation strain (15.3%) was achieved by NR-based composites filled with 10 phr BT/TA-FeIII/Ag at a low electrical field (62.2 kV/mm), which was about 2.2 fold larger than the actuation strain of the pure NR (about 7.0% at 54.7 kV/mm). Overall, this strategy could provide insights for the preparation of dielectric elastomers with high actuation strain driven by a low voltage.

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