Ionic Liquid Driven Enhancements in the Electromagnetic Interference Shielding Capabilities of Carbon-Based Polymer Composites

Electromagnetic interference (EMI) has emerged as a crucial problem in the modern world because of the rapid proliferation of electronic and telecommunication systems, which emit electromagnetic radiation that may perturb the performance of electronic devices on one hand, and could be harmful to the human body on the other [1]. As a result, considerable endeavors have been devoted to the development of efficient materials for EMI shielding/absorption. Polymers and polymeric composites with a wide array of fillers, especially carbon-based fillers have been widely used as promising candidates in the development of commercially viable EMI shielding materials. Lately, extensive research efforts have been put forward, towards effective dispersion of the fillers throughout the matrix. Ionic liquids have emerged as a promising dispersing agent for CNTs through non-covalent functionalization by interacting with the CNTs surface through π-π, cation-π or even Van der walls interaction [2]. They have been also used as fillers in metamaterial structures, where they actively engage in attenuating the electromagnetic wave thanks to their polarity [3]. Accordingly, it would be really interesting to develop a shield where we can take advantage of the already proven excellent EMI shielding capabilities of carbon based composites and in exploring the capabilities of ionic liquids in a more active manner in a polymer matrix.<br/>Here, we demonstrate the use of carbon-based nanomaterials (MWCNT, Graphene derivatives) incorporated in ionogels as effective EMI shields. These ionogels combine the unique properties of ionic liquids and their ability to attenuate the electromagnetic wave through dipole reorientation and translational motion (movement of the ions). The structural support is provided by the gel matrix, which also aids in matching the impedance of the shield with the surrounding environment, while the presence of carbon-based nanomaterials not only facilitated the formation of conductive pathways but also introduced interfacial polarization and dipole polarization between them and the ionic liquid-gel matrix. The ionogels exhibited remarkable performances across a wide frequency range, where the presence of the ionic liquid led to an enhanced absorption of the electromagnetic wave, with over 97% attenuation, of which over 55% is by absorption. Morphological characterizations revealed the homogeneous envelopment of the CNTs by the ionic liquid enhancing the interfacial polarization. The electrical conductivity measurements confirmed the conductive behavior of the carbon-based nanomaterial incorporated ionogels, which is essential for effective EMI shielding.<br/><br/>[1]: S. Driessen et al. Ep Europace, vol. 21, no. 2, p. 219-229, (2019).<br/>[2] : Lopes Pereira, et al. Journal of Applied Polymer Science, vol. 133, no. 38 (2016).<br/>[3] : Yang, Fulong, et al. Applied Physics A, vol. 125, p. 1-9 (2019).