Zwitterions Raise the Dielectric Constant of Soft Materials,Physical Review Letters

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Zwitterions Raise the Dielectric Constant of Soft Materials
Physical Review Letters ( IF 8.1 ) Pub Date : 2021-11-24 , DOI: 10.1103/physrevlett.127.228001
Wenwen Mei ₁ , August J Rothenberger ₁ , Joshua E Bostwick ₁ , Joshua M Rinehart ₁ , Robert J Hickey ₁ , Ralph H Colby ₁

Affiliation

Materials exhibiting high dielectric constants (

ϵ_{s}

) are critical for energy storage and actuators. A successful approach to increase

ϵ_{s}

is to incorporate polar additives (with high

ϵ_{s}

) but controlling the resulting dispersion state is difficult. Here, we show that significant

ϵ_{s}

increases are realized by adding zwitterions, which are small molecules with a cation and an anion separated by covalent bonds. The increase in

ϵ_{s}

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

ϵ_{s}

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