Stress controllability in thermal and electrical conductivity is important for flexible piezoresistive devices. Due to the strength‐elasticity trade‐off, comprehensive investigation of stress‐controllable conduction in elastic high‐modulus polymers is challenging. Here presented is a 3D elastic graphene‐crosslinked carbon nanotube sponge/polyimide (Gw‐CNT/PI) nanocomposite. Graphene welding at the junction enables both phonon and electron transfer as well as avoids interfacial slippage during cyclic compression. The uniform Gw‐CNT/PI comprising a high‐modulus PI deposited on a porous templated network combines stress‐controllable thermal/electrical conductivity and cyclic elastic deformation. The uniform composites show different variation trends controlled by the porosity due to different phonon and electron conduction mechanisms. A relatively high k (3.24 W m−1 K−1, 1620% higher than PI) and suitable compressibility (16.5% under 1 MPa compression) enables the application of the composite in flexible elastic thermal interface conductors, which is further analyzed by finite element simulations. The interconnected network favors a high stress‐sensitive electrical conductivity (sensitivity, 973% at 9.6% strain). Thus, the Gw‐CNT/PI composite can be an important candidate material for piezoresistive sensors upon porosity optimization based on stress‐controllable thermal or electrical conductivity. The results provide insights toward controlling the stress‐induced thermal/electrical conductivities of 3D interconnected templated composite networks for piezoresistive conductors or sensors.
Thermally
conductive, robust, but self-healable polymer/carbon
nanocomposites are the research focus in functional materials. However,
the trade-off between molecular interaction and cross-linking makes
it difficult to simultaneously achieve excellent self-healing, high
strength, and thermal conduction. Herein, we fabricated boroxine poly(dimethylsiloxane)
2-ureido-4[1H]-pyrimidinone selectively cross-linked
by molecular boron ester bonds and hydrogen bonds. By optimizing the
reversible interaction, a maximum strength of 7.33 MPa and a high
self-healing efficiency of 97.69 ± 0.33% were achieved at a boroxine-to-2-ureido-4[1H]-pyrimidinone molar ratio of 1:3 (BE-PDMS1:3-UPy). Highly robust composites of BE-PDMS1:3-UPy were
obtained using a UPy-modified graphene aerogel. A transected sample
recovered its mechanical properties (78.83 ± 2.40%) and thermal
conductivity (98.27 ± 0.13%) after self-healing at 40 °C
for 6 h. The outstanding reversible association/disassociation of
hydrogen bonds at the polymer–graphene interface makes the
composites to be used as structure–function integrated materials
in interfacial thermal conductors.
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