Polyethylene glycol modified polysiloxane and silver decorated expanded graphite composites with high thermal conductivity, EMI shielding, and leakage-free performance

Abstract

Phase change thermal interface materials (PCTIMs) have attracted significant attention due to their dual capability in temperature control and thermal buffering. However, the widespread application of PCTIMs in electronic devices is hindered by critical drawbacks such as low thermal conductivity (к), absence of electromagnetic interference shielding effectiveness (EMI SE), poor flexibility, and susceptibility to leakage. In this study, leakage-free PCTIMs were successfully fabricated with ultra-high thermal conductivity (к_∥ = 23.4 W m⁻¹ K⁻¹, к_⊥ = 8.1 W m⁻¹ K⁻¹), outstanding phase change functionality, exceptional EMI SE (73.2 dB), and excellent flexibility. A polyethylene glycol-modified polydimethylsiloxane (pPDMS) was synthesized through chemical grafting, demonstrating its significant potential as substrates for PCTIMs. Moreover, a designed material called silver nanoparticles-decorated expanded graphite (Ag-EG), was prepared to facilitate multidimensional material collaboration and incorporated into the pPDMS matrix to obtain Ag-EG@pPDMS composites. This integration resulted in a three-dimensional (3D) multi-layer orientation structure that enabled superior thermal conductivity in both in-plane and through-plane directions. To investigate the influence of 3D multi-layer orientation structure on Ag-EG@pPDMS, theoretical analysis was conducted using Effective Medium Theory (EMT) and Foygel thermal conduction models, which were further simulated by finite element analysis confirming substantial enhancement in material properties attributed to the 3D multi-layer orientation structure. Thermal management and electromagnetic interference (EMI) shielding applications were conducted using computers, wireless bluetooth earphones, and other electronic devices, indicating the superior thermal conductivity and EMI shielding of Ag-EG@pPDMS composites.