Dynamic ionic crosslinking, graft polyethylene glycol-based polymeric phase change materials networks with ultrahigh latent heat efficiency and recycling ability

Abstract

Polymeric polyethylene glycol (PEG)-based phase change materials (PCMs) present the intrinsic shape-stable essence, tunable phase change properties and mechanical strength, yet most of polymeric PCMs present a relatively low latent heat density (<120 J/g) and efficiency (<0.7), non-recycling ability resulting from the covalent crosslinking structure. Herein, the graft PCMs (GPCMs) with graft PEG side chains were synthesized via the dynamic ionic crosslinking reaction of carboxyl-functionalized graft PEGs and citric acid as the carboxyl co-donors with divalent zinc cations. The phase change and rheological properties of the GPCMs can be readily tuned by the length of PEG side chains and the loading content of citric acid. The highest latent heat density and efficiency of the GPCMs reach up to 155.0 J/g and ∼1, respectively, resulting from the synergistic effect of the ionic bonding and graft PEG side chains. The GPCMs present the shape-stable solid-solid phase transition behavior, high thermal reliability and stability, photothermal properties by compositing carbon black and excellent solvent-induced dissolving ability resulting from the nature of dynamic ionic crosslinking. The design of dynamic ionic crosslinking GPCMs structure will provide a robust, versatile access to the combination of high latent heat density and efficiency, high mechanical strength, recycling ability in a single organic PCMs.