Deformable and highly adhesive poly(ionic liquid)/liquid metal visco-elastomers for thermal management

Abstract

The rapid advancements in high-density packaging underscore the critical demand for advanced thermal interface materials (TIMs). Developing TIMs with exceptional mechanical flexibility, robust interfacial adhesion, minimal thermal resistance, and superior thermal stability presents a significant challenge. Here, we introduce poly(ionic liquid)s (PILs) as the matrices for TIMs, representing an initial investigation into the feasibility of PIL-based TIMs. Specifically, poly(1-octyl-3-vinylimidazole) bis(trifluoromethanesulfonyl)imide (P[OVIm]NTf₂) shows a remarkable tensile elongation (>2300%), strong interfacial adhesion (6.9 MPa with steel, 6.6 MPa with copper), elevated thermal decomposition temperature (>240 °C in air), excellent thermal stability (no mass loss at 150 °C), rapid self-healing capability, and reprocessability. As a proof of concept, liquid metal (LM) was utilized as a filler within P[OVIm]NTf₂ matrix to fabricate TIMs containing a substantial LM content (>60 vol%). The P[OVIm]NTf₂/LM visco-elastomers achieve a remarkable thermal conductivity of 3.2 W m⁻¹ K⁻¹. Furthermore, the composites display an elongation of 109% while maintaining strong interfacial adhesion (0.95 MPa) with steel. In a practical application scenario, the P[OVIm]NTf₂/LM visco-elastomers efficiently disperse heat, highlighting their potential practical utility. This study presents a novel approach by advocating the use of PILs as an alternative to conventional silicone matrices, thereby validating the potential application of PILs in the TIM domain.