Reversible thermochromic microcapsules with SiO2 shell for indicating temperature and thermoregulation

In this study, we successfully designed and synthesized a series of thermochromic phase change microcapsules with different core-shell ratios. Reversible thermochromic phase-change material systems (TC-PCMs) with excellent color-change performance were prepared as the core materials by selecting the components of the three-component thermochromic compound, and then the SiO2 shell was assembled on the interface of TC-PCMs droplets in oil-water emulsion by interfacial polymerization. The microstructure and chemical composition of the resulting microcapsules were investigated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). SEM images showed that these microcapsules have spherical shape and well-defined core-shell structure. According to differential scanning calorimeter (DSC) and thermogravimetric analysis (TG) tests, these bifunctional microcapsules exhibited excellent heat storage and release properties, high heat storage capacity and good thermal stability. The melting and solidifying enthalpies of microPCMs were 181.3 J/g and 174.5 J/g, respectively. In addition, the resulting microcapsules have good thermochromic reversibility with a color transition temperature of 52 °C. The thermal conductivity of TC-PCMs was enhanced by 132.4 % after loading SiO2 shells. Furthermore, these microcapsules exceeded the target temperature and successfully achieved the thermochromic function. The bifunctional microcapsules developed in this study have great potential for application in textiles, smart material coatings, luminescent thermal sensors and anti-counterfeiting.