Functionalized carbon nanotubes as phase change materials with enhanced thermal, electrical conductivity, light-to-thermal, and electro-to-thermal performances

Light- and electro-driven hexadecyl acrylate-functionalized single/multi-wall carbon nanotubes (HDA-g-SWCNT, HDA-g-MWCNT) solid-solid phase change materials (SSPCMs) were fabricated via a green Diels-Alder reaction. Both HDA-g-SWCNT and HDA-g-MWCNT show enhanced thermal and electrical conductivities, appropriate phase change temperature, almost no supercooling degree and effective phase change enthalpy. HDA was covalently grafted onto the surface of SWCNT/MWCNT. The phase transition enthalpy (Delta H-h) and phase transition temperature (T-hp) in the heating process, crystallization enthalpy (Delta H-C) and crystallization temperature (T-cp) in the cooling process of HDA-g-SWCNT are 52 J/g, 36.7 degrees C, 51 J/g, and 23.7 degrees C, respectively. The Delta H-h, Delta(hp), Delta H-c, and T-cp of HDA-g-SWCNT are 40 J/g, 38.0 degrees C, 39 J/g, and 26.8 degrees C, respectively. The HDA-g-SWCNT/HDA-g-MWCNT can effectively convert electric or light energy into thermal energy under electric field or solar illumination. Meanwhile, the electrical conductivity of HDA-g-SWCNT and HDA-g-MWCNT films reached up to 718 and 389 S/m, respectively. The phase change property and enhanced thermal conductivity of HDA-g-SWCNT and HDA-g-MWCNT enable them to be used as a heat spreader for electronic cooling applications. Furthermore, the HDA-g-SWCNT and HDA-g-MWCNT exhibited good thermal stability, great thermal reliability, and shape stability, potentially leading to new energy systems with multi-responsive performance for electronic devices, solar energy utilization, and thermal management. (C) 2019 Published by Elsevier Ltd.