In the mid-20th century, the theories regarding the highly layered crystalline structure of the carbon element were validated when single layers of graphite were directly observed using transmission electron microscopy. These observations confirmed the theoretically predicted extraordinary properties of these single layers, for which the term “graphene” was coined. These properties included a Young's modulus of 1 TPa and electrical/thermal conductivity comparable to copper, sparking scientific efforts to synthesize graphene from bulk graphite. This endeavor culminated in the awarding of the 2010 Physics Nobel Prize “for groundbreaking experiments regarding the two-dimensional material”, six years after the first successful isolation of graphene using common adhesive tape. Subsequently, numerous experimental studies and simulations have explored graphene's potential in diverse fields, such as electronics, opto-electronics, energy storage, and electromagnetic interference (EMI) shielding.

Among the extensively researched applications, the incorporation of graphene as a multifunctional additive into various polymeric matrices has significantly advanced the field of conductive polymer composites (CPCs). This has led to considerations of graphene-based CPCs as EMI shielding materials across various sectors. However, studies have revealed that the electromagnetic behaviors of these materials are complex and influenced by a multitude of physical, compositional, and (micro)structural factors.

The theoretical and experimental investigations within this PhD thesis represent a comprehensive examination of the electromagnetic behavior of CPCs. This is achieved by bridging the nanoscale characteristics of the additives and the microstructure of the composite material to the macroscopic performance. To this end, two families of graphene morphologies, namely graphene nanoplatelets (GNPs) and graphene nanoribbons (GNRs), are studied. This research encompasses the analysis of the complex dielectric response and mechanical characteristics of graphene-based biphasic and hybrid CPCs composed of multiple dispersed micro- and/or nano-fillers. In light of the presented findings, this PhD research plays a pivotal role in facilitating the translation of multiscale factors into the optimized performance of graphene-based CPCs for real-world applications.