A new finding of reverse three-component thermochromic pigments using biomass-derived l-ascorbyl palmitate color developer

Abstract

The fatty alcohol phase change material is used as the solvent for three-component thermochromic pigment (the leuco dye-color developer-solvent), which has the dual functions of both thermochromism and thermal energy storage. However, bisphenol A is usually used as the color developer of the three-component thermochromic pigments currently, which has potential safety hazards and is not conducive to market promotion. For most three-component thermochromic pigments, their colors change from colored to colorless. Here, we prepare the biomass-derived thermochromic pigment (TC-LAP) by using l-ascorbate palmitate (LAP) as a color developer, crystalline violet lactone (CVL) as a leuco dye, and tetradecanol (TD) as a solvent. Interestingly, a special reverse thermochromic phenomenon of endothermic color deepening is found. Heating causes the discoloration of TC-LAP from colorless to colored. Thermal energy storage and reverse thermochromic are realized and devoid of safety hazards. The color of TC-LAP thermochromic pigment changes from white to blue with heating, and the CIE 1931 chroma coordinates change from X = 0.21, Y = 0.26 to X = 0.36, Y = 0.36. For the TC-LAP thermochromic pigment, the chromaticity coordinates of blue (X = 0.36, Y = 0.36) correspond to the energy storage of 179.91 J/g and the discoloration temperature of 40 °C. Reverse thermochromism is an exciting discovery for the color diversity of low temperature and controlled three-component thermochromic pigment. Meanwhile, the use of biomass-derived LAP also alleviates the safety hazard of BPA color developer in three-component thermochromic pigment.