“One stone, two birds” solvent system to fabricate microcrystalline cellulose–Ti₃C₂T_x nanocomposite film as a flexible dielectric and thermally conductive material

A strategy for fabricating microcrystalline cellulose–Ti₃C₂T_x (MCC–MXene) nanocomposite films with high relative permittivity, high thermal conductivity, and excellent mechanical properties was developed. The MCC–MXene nanocomposite film was fabricated by casting a solution containing N,N-dimethylacetamide/lithium chloride (DMAc/LiCl)-soluble MCC and DMAc-dispersible MXene nanosheets, followed by humidity control drying. The MXene nanosheets greatly enhanced the permittivity of the nanocomposite films owing to interfacial polarization. Thus, the nanocomposite film with 20 wt.% MXene content achieved a desirable permittivity of 71.4 at 10² Hz (a 770% improvement against that of neat cellulose), while the dielectric loss only increased by 1.8 times (from 0.39 to 0.70). The obtained nanocomposite films with 20 wt.% and 30 wt.% MXene exhibited remarkable in-plane thermal conductivities of 8.523 and 9.668 W∙m⁻¹∙K⁻¹, respectively, owing to the uniform dispersion and self-alignment of the MXene layered structure. Additionally, the uniformly dispersed MXene nanosheets in the MCC network with interfacial interaction (hydrogen bonding) and mechanical entanglement endowed the nanocomposite films with excellent mechanical properties and flexibility. Furthermore, the thermal stability, water resistance, and antibacterial properties of the nanocomposite films were effectively improved with the introduction of MXene. Moreover, using DMAc/LiCl as the solvent system not only improves the compatibility between MCC and MXene but also avoids the problem of easy oxidation of MXene in aqueous systems. With the high stability of the MCC–MXene solution and enhanced properties of the MCC–MXene films, the proposed strategy manifests great potential for fabricating natural biomass-based dielectric materials.