Authors: Aming Xie | Fan Wu | Jiang Lai | Jiale Wu | Long Qin | Fangyuan Chu | Han Gao | Hongcheng Shang | Weijin Li | Haibo Zeng
Source: Chinese Science Bulletin (Chinese Version) (article, 2023-04-01)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Progress and future challenges of molecular conductive polymers-based microwave absorption materials <p indent="0mm">The fast development of telecommunications equipment, digital systems and electronic devices has brought the potential threat of electromagnetic (EM) wave pollution/interference to our daily life and stealth in the military. Microwave absorbers are a kind of materials that can convert EM energy into thermal energy or other dispersible energy. Developing microwave absorbers with high heat and chemical resistance, lightweight, minimal coating thickness, wide bandwidth, and strong absorption strength is highly desired. Although various materials such as metals, metal oxides, graphene and carbon black, are reported as candidates for microwave absorbers; traditional metal absorbing materials have the problems of high density, difficult-to-control microstructure, easy corrosion and difficult processing. Meanwhile, traditional carbon-based absorbing materials (e.g., graphene, graphite and carbon black) have problems such as narrow absorption bands and weak strength and cannot satisfy the demand for increasingly lightweight, integrated and high-performance electronic products and equipment. Thanks to their unique physicochemical properties, molecule-based conductive absorbing materials have shown good absorbing potential and have attracted the interest of researchers in recent years. In this paper, we reviewed the recently reported research on molecule-based conductive absorbing materials. Initially, the research progress of the absorption principle of molecular-based conductive absorbing materials is highlighted. The microwave absorption principles of conductive polymers, such as electron conductance and microwave attenuation, polarization relaxation and microwave energy loss of molecular polar groups, and microwave response and energy attenuation effects of molecular polymer networks, are introduced. Subsequently, the three major types of materials in molecular-based conductive absorbing materials, namely conductive polymers (e.g., ferrocene absorbing materials), conductive conjugated polymers (e.g., polyaniline and polyvinylpyrrolidone) and conductive metal-organic complex absorbing materials (e.g., copper 4-hydroxybenzenethiol, copper thiophenolates and M<sub>3</sub>(HHTP)<sub>2</sub> (M=Zn, Ni, Co, Cu; HHTP=2,3,6,7,10,11-hexahydroxytriphenyl hydrate)), are discussed. Besides, the structural design control strategies and absorption loss mechanisms of the intrinsic conductive polymers are discussed. Single molecule-based conductive materials often face the difficulty for practical applications in microwave absorption. Thanks to the advantages of flexible structure design, good compatibility with embedded guest molecules, intermolecular interaction with guest molecules and certain intrinsic microwave absorption properties, molecule-based conductive materials are able to be included with conductive filler materials (e.g., metal nanoparticles, carbon black, graphene and carbon nanotubes) and further suit the application of electromagnetic absorption. Therefore, the composites prepared by the molecule-based conductive materials and other conductive fillers (e.g., metal nanoparticles, carbon black, graphene and carbon nanotubes) are reviewed for electromagnetic absorption applications. Then, the typical methods for preparing molecular conductive electromagnetic wave absorption materials are screened. Particularly, the molecular layer deposition method and molecular post-modification method of two-dimension materials for preparing electromagnetic wave absorption materials are focused on. Finally, the challenges (e.g., in-depth understanding and interpretation of the absorption mechanism between electron delocalization structures and electromagnetic waves, achieving EM wave absorption materials with strong heat resistance, chemical stability, and multi-frequency electromagnetic wave absorption properties, intelligent design, and integrated functionality of the composites) to be solved in future research of molecular-based conductive absorbing materials are pointed out. Microwave ; Materials science ; Polymer ; Electrical conductor ; Conductive polymer ; Absorption (acoustics) ; Nanotechnology ; Polymer science ; Engineering physics ; Computer science ; Engineering ; Composite material ; Telecommunications Electromagnetic wave absorption materials ; Conducting polymers and applications ; Flame retardant materials and properties