Covalently Functionalized Leakage-Free Healable Phase-Change Interface Materials for Thermal Management

Thermally conductive polymer-matrix nanocomposites have received considerable attention for the thermal management of electrical and mechanical devices. The thermal interface material (TIM) fills the inevitable gap between the heat source and sink for efficient heat removal. We have investigated TIMs by employing silver (Ag) flakes and multi-walled carbon nanotubes embellished with Ag nanoparticles (nAgMWNTs) to impart thermal conductivity (<i>κ</i>) due to the intrinsically insulating nature of matrix materials [1, 2]. Phase change material (PCM) has received considerable attention as a matrix material because the solid-liquid phase change increases conformality between mating surfaces, taking advantage of both pad-type and grease-type TIMs [3]. However, the leakage of PCM, low <i>κ</i>, and non-healability have impeded the practical applications of PCM-TIMs. Here we report a leakage-free healable PCM-TIM by covalently functionalizing octadecanol (PCM) with polyethylene-co-methyl acrylate-co-glycidyl methacrylate (polymer) through the epoxy ring opening reaction [3]. The PCM undergoes a semi-crystalline to amorphous phase change, preventing leakage. The nAgMWNTs construct thermal percolation pathways between Ag flake islands, resulting in the record-high thermal conductivity (43.4 W m^-1K^-1) and low thermal resistance (30.5 mm²K W^-1), compared with PCM-TIMs in literature [3]. The carbonyl (C=O) and hydroxyl (O-H) groups enable reversible hydrogen bonding, realizing a nearly perfect healing efficiency. Excellent heat dissipation demonstration is carried out [3]. The recent progress in our laboratory will also be introduced including non-oxidizing copper nanoparticles [4, 5] and electron-tunneling transport studies [6, 7]. References: [1] Advanced Materials, 28, 7220 (2016) [2] Small, 17, 2102128 (2021) [3] Advanced Materials, 35, 2300956 (2023) [4] Materials Today, 48, 59 (2021) [5] Advanced Functional Materials, 33, 2304776 (2023) [6] Nature Communications, 11, 2252 (2020) [7] Science Advances, 8, eabn3365 (2022)