Preparation of mechanically robust and thermochromic phase change materials for thermal energy storage and temperature indicator

•Mechanically robust and thermochromic SSPCMs were successfully prepared.•These Micro-HPCMs possess outstanding reversible thermochromic function.•The tensile strength of Micro-HPCM4K can arrive at the maximum of 14.8 MPa.•The thermochromic SSPCMs have good thermal energy storage ability of 113.4 J g−1. Phase change materials (PCMs) capable of thermal energy storage (TES) have been drawn great attention as an important strategy to deal with energy shortage. Herein, a novel thermochromic solid–solid PCMs (SSPCMs) based on polyethylene glycol has been successfully synthesized, which possess mechanically robust properties and intriguingly thermochromic function besides TES. These devised thermochromic SSPCMs hold high melting latent heats with a maximum value at 113.4 J g−1. Additionally, the highest ultimate tensile strength of prepared SSPCMs featuring with excellent stretchability (658.3%) can reach 14.8Mpa, endowing them with the practical application for more scenarios. Particularly, these thermochromic SSPCMs can change itself color from purple to pink during the phase transition process, which can be acted as a temperature indicator. Surprisingly, the color of the thermochromic SSPCMs can change in just 3 s under 90 ℃, rapidly responding the change of external temperature. For this, these thermochromic SSPCMs can be coated on delivery pipeline, which not only plays thermal insulation function, but also makes the corresponding color change by sensing the change of liquid temperature in the pipeline for playing a warning role. Combination of color change function and thermal energy storage in the devised SSPCMs not only realizes the storage and release of latent heat, but also provides real-time indication of the saturation-depletion state of energy. This design route provides an attractive way to solve the dilemma of traditional PCMs with a single TES function and broaden its applied fields.