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Zwitterions Raise the Dielectric Constant of Soft Materials

Wenwen Mei, August J. Rothenberger, Joshua E. Bostwick, Joshua M. Rinehart, Robert J. Hickey, and Ralph H. Colby
Phys. Rev. Lett. 127, 228001 – Published 24 November 2021
Physics logo See synopsis: Simple Additives Make Polar Fluids More Polar
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Abstract

Materials exhibiting high dielectric constants (ϵs) are critical for energy storage and actuators. A successful approach to increase ϵs is to incorporate polar additives (with high ϵs) but controlling the resulting dispersion state is difficult. Here, we show that significant ϵs increases are realized by adding zwitterions, which are small molecules with a cation and an anion separated by covalent bonds. The increase in ϵs with zwitterion addition is attributed to the large molecular dipole of zwitterions, ranging from 35 to 41 D, as experimentally quantified and confirmed using density functional theory. At elevated zwitterion concentration in an ethylene glycol medium, there is a nonlinear increase of ϵs 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 ϵs in soft materials.

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  • Received 29 June 2021
  • Accepted 21 October 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.228001

© 2021 American Physical Society

Physics Subject Headings (PhySH)

Polymers & Soft Matter

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Simple Additives Make Polar Fluids More Polar

Published 24 November 2021

The strong polar nature of bonded molecular pairs called zwitterions boosts the dielectric constants of polar fluids.

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Authors & Affiliations

Wenwen Mei, August J. Rothenberger, Joshua E. Bostwick, Joshua M. Rinehart, Robert J. Hickey, and Ralph H. Colby

  • Materials Science and Engineering, Penn State University, University Park, Pennsylvania 16802, USA

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Issue

Vol. 127, Iss. 22 — 24 November 2021

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