The development of conductive polymer composites (CPCs) and foams offers a promising solution for achieving absorption-dominant electromagnetic interference (EMI) shielding while mitigating secondary electromagnetic pollution. Despite the significance of structural and geometrical factors in creating high-performance absorption-dominant EMI shielding materials, systematic structure-property (i.e., EM wave reflection efficiency) relationships have rarely been reported for these materials. Therefore, this dissertation aims to demonstrate how theoretical computation and experimental design can be integrated to overcome the challenges of structural design and optimization of absorption-dominant EMI shielding CPCs for cutting-edge applications.

The first part of the thesis includes an in-depth understanding of the effects of cellular structure and geometry on the EMI shielding properties of single-layer EMI shielding CPCs and foams. An input impedance model was applied to explore the thickness dependency of reflectivity (R) in microcellular CPC foams and then decouple the effect of thickness on the R-value from other structural variables, such as the void fraction and cellular morphology. In particular, the presence of microcellular structure can effectively tune the input impedance matching while maintaining a satisfactory EMI shielding effectiveness, resulting in a reduced R and enhanced absorption-to-reflection ratio at optimal thickness. The second part of this thesis demonstrates a theoretically guided approach to designing and fabricating bilayer gradient CPC systems that offer advanced absorption characteristics for EMI shielding. These systems comprise an absorption layer that dissipates the EMI energy and a shielding layer that reflects and shields the remaining energy. Heterostructured SiC nanowire/MXene (Ti3C2Tx) nanosheet hybrids were developed in the absorption layer via interface engineering, which revealed an improved EM energy dissipation capability and satisfactory impedance matching in theoretical results. Moreover, the input impedance of the bilayer CPC systems can be effectively tuned by optimizing the microstructure and geometry of both absorption and shielding layers via theoretical computations, achieving absorption-dominant EMI shielding performance with broadband ultralow reflectivity and a controlled sample thickness.

This dissertation developed a fundamental understanding of structure-property relationships and proposed new methods to develop and fabricate CPCs and foams for achieving high-performance absorption-dominant EMI shielding.