Zwitterions Raise the Dielectric Constant of Soft Materials

Abstract

Materials exhibiting high dielectric constants (𝜀𝜀 𝑠𝑠 ) are critical for energy storage and actuators. A successful approach to increase 𝜀𝜀 𝑠𝑠 by incorporating polar additives (with high 𝜀𝜀 𝑠𝑠 ) but controlling the resulting dispersion state is difficult. Here, we show that significant 𝜀𝜀 𝑠𝑠 increases are realized by adding zwitterions, which are small molecules with a cation and an anion separated by covalent bonds. The increase in 𝜀𝜀 𝑠𝑠 with zwitterion addition is attributed to the large molecular dipole of zwitterions, ranging from 35 to 41 Debye, as experimentally quantified, and confirmed using density functional theory. At elevated zwitterion concentration in an ethylene glycol medium, there is a non-linear increase of 𝜀𝜀 𝑠𝑠 that eventually saturates due to the strong Coulombic interactions between zwitterions. The presented work provides a fundamental molecular understanding of why zwitterions are effective additives in boosting 𝜀𝜀 𝑠𝑠 in soft materials.

Design of Polymeric Zwitterionic Solid Electrolytes with Superionic Lithium Transport

“…Recent studies have pointed toward the promising properties of zwitterions in electrochemical applications both as an ion transport matrix 37 and as a means to increase the dielectric constant of an electrolyte. 38 …”

Viscoelastic and Properties of Amphiphilic Chitin in Plasticised Polylactic Acid/Starch Biocomposite

“…The single relaxation peaks of the DMA analysis can further be double-checked using the Cole–Cole analysis of viscoelastic response [ 44 , 45 ]. Cole–Cole is a method of analysing dielectric relaxation data that involves graphing E″ versus E′, with each point representing one frequency [ 45 , 46 ].…”

Frequency-Dependent Dielectric Permittivity in Poisson–Nernst–Planck Model

“…In Figure , the real (a) and imaginary (b) parts of ϵ as a function of Log­(ω/2π) are shown. The dotted red curve represents the experimental data obtained in ref , and the solid black line is given by eq . Some parameters considered in Figure are obtained from the experimental measurement, such as A = 3.1 × 10 –4 m 2 , l = 50 × 10 –6 m, ϵ ∞ = 8.6, ϵ s = 270, and ϵ 0 = 8.85 × 10 –12 C/(V ·m).…”

“…The evidence of low relaxation frequency has been reported and credited to an exchange process between bulk, molecular and macromolecular materials and metal surfaces . More recently, an apparent DC conductivity has also been observed in small molecules connecting a cation and an anion by a covalent bond . Such apparent DC conductivity has been hypothesized to be caused by the enormous dipoles of zwitterions rotation under the alternating AC field …”

“…More recently, an apparent DC conductivity has also been observed in small molecules connecting a cation and an anion by a covalent bond . Such apparent DC conductivity has been hypothesized to be caused by the enormous dipoles of zwitterions rotation under the alternating AC field …”