Polyaniline nano-composites with large negative dielectric permittivity

Abstract

Two polyaniline (PANI)/polymer nano-composites exhibiting huge negative dielectric permittivity have been synthesized for the first time. These novel chemical processes open a new approach for fabrication of the negative index materials (NIMs), since most of the NIMs prepared today are obtained by a structural approach – by putting together two structured materials that exhibit separately a negative permittivity and a negative permeability. We found the negative permittivity of these nano-composites is a function of the content of the dopant (i.e., PANI) as well as of the frequency. The generation of huge negative permittivity can be rationalized by the well-dispersed PANI-DBSA nano-particles which form a pseudo-continuous conductive pathway in these nano-composites.

Preparation of Iron Networks Hosted in Porous Alumina with Tunable Negative Permittivity and Permeability

“…The negative permittivity was considered to be resulted from the formation of continuous conductive pathways in the composites. Similar negative permittivity phenomenon was also reported in carbon nanofiber/polyetherimide composites13, 26 and polyaniline nano‐composites 27. Furthermore, the plasma‐like negative permittivity behavior of 600‐Fe27 was fitted using Drude model:28 ϵ r ′( ω ) = 1‐ ω p 2 /(ω 2 +ω τ 2 ), ω p = [ n eff e 2 /( m eff ϵ 0 )] 1/2 , where ω p ( ω p = 2π f p ) is the plasma frequency, ω frequency of electric field, ω τ damping parameter, ϵ 0 permittivity of vacuum (8.85 × 10 −12 F/m )′ n eff effective concentration of delocalized electrons, m eff effective weight of electron, and e electron charge (1.6 × 10 −19 C).…”

Polyaniline nanocomposites with negative permittivity

“…However, a positive dielectric constant (10–100) was observed in PANI/epoxy composites fabricated with the blending method; this means that the charge carriers were localized within the domains and could not hop to the adjacent regions. They also prepared a PANI–dodecylbenzene sulfonic acid (DBSA)/poly(acrylic acid) system with a reversed micelle method (Figure ) . Briefly, PANI was synthesized via the emulsion polymerization of aniline (Ani.)…”

On the frequency dependent negative dielectric constant behavior in Al/Co-doped (PVC+TCNQ)/p-Si structures

“…If the imaginary part is positive the effective terminal behavior is capacitive and if it is negative the effective terminal effect is inductive. [6][7][8][9][10][11] In recent years, some researchers have reported a negative capacitance (NC) [6][7][8][9][10][11][12][13] or negative dielectric constant (NDC) [14][15][16] in the forward bias C-V characteristics in some devices. The observation of NDC and NC are important because they imply that an increment of bias voltage produces a decrease in the charge on the electrodes.…”