MXene-Vitrimer Nanocomposites: Photo-Thermal Repair, Reinforcement, and Conductivity at Low Volume Fractions Through a Percolative Voronoi-Inspired Microstructure

Abstract

An innovative process to multifunctional vitrimer nanocomposites with a percolative MXene minor phase is reported, marking a significant advancement in creating stimuli-repairable, reinforced, sustainable, and conductive nanocomposites at diminished loadings. This achievement arises from a Voronoi-inspired biphasic morphological design via a straight-forward three-step process involving ambient-condition precipitation polymerization of micron-sized prepolymer powders, aqueous powder-coating with 2D MXene (Ti₃C₂T_z), and melt-pressing of MXene-coated powders into crosslinked films. Due to the formation of MXene-rich boundaries between thiourethane vitrimer domains in a pervasive low-volume fraction conductive network, a low percolation threshold (≈0.19 vol.%) and conductive polymeric nanocomposites (≈350 S m⁻¹) are achieved. The embedded MXene skeleton mechanically bolsters the vitrimer at intermediate loadings, enhancing the modulus and toughness by 300% and 50%, respectively, without mechanical detriment compared to the neat vitrimer. The vitrimer's dynamic-covalent bonds and MXene's photo-thermal conversion properties enable repair in minutes through short-term thermal treatments for full macroscopic mechanical restoration or in seconds under 785 nm light for rapid localized surface repair. This versatile fabrication method to nanocoated pre-vitrimer powders and morphologically complex nanocomposites is compatible with classic composite manufacturing, and when coupled with the material's exceptional properties, holds immense potential for revolutionizing advanced composites and inspiring next-generation smart materials.