Mechanically robust nacre-mimetic framework constructed polypyrrole-doped graphene/nanofiber nanocomposites with improved thermal electrical properties

Nacre mimetics show great potential as mechanically robust, lightweight, and promising functional materials. Herein, we report a nanostructured nacre-mimetic hybrid framework, prepared via in situ self-polymerization of tannic acid (TA) and pyrrole monomer on cellulose nanofiber (CNF)-anchored graphene nanosheets (GNs), as a two-dimensional interconnected network (designated as TA@PG-CNF) to fabricate mechanically robust and thermally and electrically conductive composites. A unique network structure with a combination of conductive polypyrrole (PPy) protrusions and multiscale nanofibers/nanoplates was obtained, where the nanohybrid protrusions acted as bridges that link the adjacent GNs and nanofibers. As a result, a composite with low filler loading (10.0 wt%) exhibited advantages for the combination of all properties, i.e., enhanced electrical and thermal conductivity (6.52 S cm⁻¹ and 7.81 W m⁻¹ K⁻¹), high tensile strength (217.9 MPa), and good toughness (19.6 MJ m⁻³). We attribute the enhancement of these properties to the construction of an interconnected TA@PG-CNF skeleton and the oriented "brick-and-mortar" structure based on GNs blocks and the polyvinyl alcohol matrix, in which a mechanically robust conductive network was constructed. We envision that the relevant functionalities can be integrated into stiff and strong bioinspired materials as flexible microelectronic candidates.