Zwitterionic Polymers for Capacitance Applications

With the advent of sustainable and renewable energy technologies, there is an ever-growing demand to improve energy storage devices such as supercapacitors. One such way to improve supercapacitors is to increase its capacitance with high-dielectric mediums, although most materials rarely exceed the dielectric constant of water (ε = 80). Zwitterionic polymers, however, are promising materials recently reported experimentally to have dielectric constants on the order of hundreds. Using a simple incompressible discrete gaussian-chain mean-field theory with electrostatic interactions, we demonstrate that zwitterionic polymers exhibit dielectric constants on the order of hundreds. We also predict nonmonotonicity in dielectric constant as a function of chain length, leading to an optimal dielectric constant. Additionally, we show that the zwitterionic polymer screens electrostatic forces on short length scales near surfaces but acts as a dielectric medium in the bulk, and we characterize the nature of this screening. Lastly, we find that zwitterionic polymer capacitors display improvements over traditional electric double-layer capacitors.