In this review, the fundamentals of negative permittivity are critically discussed. Current research on polyaniline and its nanocomposites with negative permittivity are presented in detail. The reasons why these unique materials show negative permittivity are analyzed. This knowledge will be useful for future metacomposite design and manufacturing. These polymeric materials with negative permittivity are envisioned to create next-generation left-hand media for cloaking, subwavelength imaging, stealth, and invisibility applications.
