A Green Route to a Low Cost Anisotropic MoS₂/Poly(Vinylidene Fluoride) Nanocomposite with Ultrahigh Electroactive Phase and Improved Electrical and Mechanical Properties

Environment issues due to growing energy consumption have motivated great research efforts on new materials for efficient energy storage and their low cost fabrication. This study reports an energy-efficient solution route for the fabrication of a unique high permittivity nanocomposite film consisting of molybdenum disulfide (MoS₂) nanosheets spontaneously aligned in poly(vinylidene fluoride) (PVDF) via super-2D-confinement and gravity sedimentation. A simple thermal lamination was further developed to get anisotropic films with controllable thickness. Interestingly, an ultrahigh fraction (∼86% as confirmed by synchrotron radiation XRD) of β-phase PVDF was directly obtained by only 3.4 vol % of orientated MoS₂ nanosheets due to possible crystallization disturbance and synergistically reinforced electrostatic interaction and super-2D-confinement. This reveals a greener route to the desirable electroactive phase PVDF, whose formation usually requires giant electrical field or mechanical stresses. Simulation of the permittivity perpendicular to the nanosheets (up to 146 @ 100 Hz with 19.8 vol % MoS₂) also revealed anisotropy due to alignment. The permittivity and conductivity parallel to the nanosheets were much higher, showing anisotropic ratios of 3.96 and 6.14 (9.5 vol % MoS₂), respectively. Furthermore, the nanocomposite with a suitable composition showed simultaneously increased tensile strength, elongation, and energy storage density, making it promising for multifunctional field applications. The results may also improve the understanding of polymer polymorph transition and provide hints on new green pathways for novel composites.