Interfacial dielectric enhancement in MXene/PVDF nanocomposites via hydrogen bond-induced dipole modulation

Poly(vinylidene fluoride) (PVDF)-based dielectric composites utilizing two-dimensional (2D) MXenes as nanofillers have recently exhibited significantly enhanced dielectric properties and energy densities that are highly desirable for flexible electronics and electrostatic energy storage applications. However, nanoscale-resolved insights into the underlying mechanisms of the enhancement of interfacial dielectric responses in MXene/PVDF composites are still unclear and of critical importance. Herein, we perform first-principles calculations to explore quantum-informed structural and dielectric properties of Ti₃C₂T_x MXene/PVDF interfaces. It is shown that the discovered dielectric enhancement is mainly attributed to the structural and electronic variations enabled by the interfacial dipole engineering resulting from the OH-terminated MXenes, including transformation of PVDF chain dipole orientation (i.e., from parallel orientation (${\mu }_{\Vert }$${\mu }_{\Vert }$) on Ti₃C₂O₂ to perpendicular orientation (${\mu }_{\perp }$${\mu }_{\perp }$) on Ti₃C₂(OH)₂) and induced interfacial charge transfer and accumulation. The as-formed hydrogen bonding at the interface also provides strong interfacial coupling, enhanced comparability, dipole moment and bandgap manipulation, endowing the Ti₃C₂(OH)₂/PVDF nanocomposite with elevated dielectric permittivity and electric breakdown strength simultaneously. The findings in this work are envisioned to offer electronic/atomic scale understanding and intuitive guidelines for inspiring design and application of polymer-based dielectric composites via rational hydrogen bond-induced dipole modulation.