Latent heat and thermal conductivity enhancements in polyethylene glycol/polyethylene glycol-grafted graphene oxide composites

Although high-thermal conductivity fillers can enhance the thermal conductivity of organic phase change materials (PCMs), it is still difficult to simultaneously prevent the loss in latent heat. The realization of enhanced thermal conductivity without adversely affecting the latent heat of polymeric PCMs remains challenging. We report experimental results demonstrating that polyethylene glycol (PEG)-based PCM composites exhibit large latent heats beyond the expected values and significantly improved thermal conductivities. Latent heat and thermal conductivity enhancements are achieved by optimizing the interaction between the filler and PCM in the PEG/graphene oxide (GO) composites. PEG-grafted GO (PEG-g-GO) is synthesized and introduced into the PEG to regulate the interaction between the PEG base and GO. The result can be largely attributed to the enhanced GO dispersion and heightened mobility of the PEG chains. The grafted PEG in the PEG-g-GO acts as a plasticizer, leading to a considerable effect on the crystallization kinetics of the PEG in the composite PCMs, and thus the improved crystallizability. Latent heat and thermal conductivity enhancements are achieved by optimizing the interaction between the filler and PCM in the PEG/GO composites.