Nanoparticle-Enhanced β-Phase Formation in Electroactive PVDF Composites: A Review of Systems for Applications in Energy Harvesting, EMI Shielding, and Membrane Technology

With the continuous advancement of electronic devices, lightweight, flexible, and easily processable materials have gained substantial techno-commercial importance. Most electronic devices must possess a lightweight, high conductivity, high dielectric permittivity, low dielectric loss, and high breakdown strength. Hence, polymer-based piezoelectric materials are in great demand for design and development in energy storage, electromagnetic interference (EMI) shielding, and ultrafiltration applications. Among the piezoelectric polymers, poly(vinylidene fluoride) (PVDF) with a predominantly polar β-phase is the most important. However, the main drawbacks of the PVDF matrix are its relatively low electrical conductivity and dielectric permittivity, and poor energy harvesting and EMI shielding performance. In this context, the incorporation of conductive nanofillers such as reduced graphene oxides, graphene quantum dots, and carbon nanotubes in the PVDF matrix has attracted considerable interest owing to their extraordinary properties. The final properties of these piezoelectric composites depend on the preparation methods, structural conformation, processing conditions, dispersion of nanofillers in the matrix, surface modification of fillers, and specific or nonspecific interaction of the fillers with the PVDF matrix. Herein, we have critically reviewed the formation mechanism of the electroactive β-phase in PVDF, the effects of nanofillers on the phase transformation of PVDF (dispersion and specific interaction), and the correlation of β-phase PVDF piezoelectric and dielectric properties with energy harvesting, EMI shielding, and membrane applications.