Solvent-free synthesis of cellulose nanocrystal-graft-poly (ethylene glycol) as solid–solid phase change nanoparticles

Solid–solid phase change materials (SSPCMs) have drawn substantial interest due to their excellent thermal energy storage performances and shape stability. Herein, a series of solid–solid phase change nanoparticles were successfully synthesized by grafting poly (ethylene glycol) (PEG, phase change working substance) onto cellulose nanocrystals (CNCs) support in a solvent-free reaction system. The as-synthesized CNC-based solid–solid phase change nanoparticles (namely CNC-g-PEG) exhibited good thermal stability and high thermal energy storage capacity. Additionally, the latent heat and phase transition temperature of CNC-g-PEG could be adjusted by changing the molecular weight of PEG. In particular, the CNC-g-PEG4K possessed a relative high melting enthalpy and crystallization enthalpy of 120.4 and 121.9 J/g at 53.7 and 37.1 °C, respectively. The CNC-g-PEG4K also exhibited excellent thermal reliability after 100 thermal cycles and was suitable for long-term practical application. This study proposes a promising approach for constructing sustainable solid–solid phase change nanoparticles which shows considerable potential applications in thermal energy storage and temperature control. Graphical abstract