Poly(Ionic Liquid) Composites with Liquid Metal–Copper Hybrid Networks for High-Performance Thermal Interface Materials

Abstract As artificial intelligence (AI) and high-density chip packaging continue to advance, increasing power densities in electronic devices are intensifying localized heat accumulation, making high-performance thermal interface materials (TIMs) increasingly important for efficient heat dissipation and device reliability. Poly(ionic liquid)s (PILs) provide a promising platform for TIMs by combining strong interfacial adhesion, mechanical compliance, thermal stability, and compatibility with thermally conductive fillers, while avoiding volatile siloxane release associated with conventional silicone-based TIMs. Herein, poly(1-vinyl-3-ethoxyethylimidazolium bis(trifluoromethanesulfonyl)imide) (PVImO-NTf2) was used as matrix to construct liquid metal (LM)-copper (Cu) hybrid TIMs. Spherical Cu particles promoted thermally conductive pathways within the LM network, while interfacial Cu-LM interactions mitigated LM oxidation and migration, improving both heat transport and structural integrity. Surface modification of Cu with (3-chloropropyl)triethoxysilane (CPTES) suppresses excessive Ga–Cu alloying and thereby maintains processability. The CPTES-modified Cu was blended with LM at a 1:1 volume ratio to form hybrid fillers. At a total filler loading of 70 vol %, the resulting composite shows the best balanced performance, with an adhesion strength to silicon of 1.61 ± 0.03 MPa, an interfacial thermal contact resistance of 2.04 ± 0.65 × 10–6 m2 K W1–, and a thermal conductivity of 3.76 W m–1 K–1. These results demonstrate that interfacial regulation and multiphase filler synergy offer an effective route to high-performance TIMs.