Multicolor-tunable biomass thermochromic dyes utilizing tea polyphenols color developer for temperature-controlled linen fabric

Linen, an important industrial crop, is commonly used in the textile field. The development of temperature-controlled linen fabrics is important for the high-value utilization of cellulose-based industrial products. The linen fabrics with color and performance changes controlled by temperature are prepared via the vacuum impregnation process utilizing biomass three-component thermochromic dyes. Currently, three-component thermochromic dyes based on the bisphenol A (BPA) color developer have received special attention due to high saturation color and reversible color-changing performance. However, the toxicity and carcinogenicity of BPA limit its applications in security inks, decorative coatings, plastics, etc. Exploiting excellent and safe biomass color developers for three-component thermochromic dyes remains a challenge. Tea polyphenols (TP) are proposed as alternatives to BPA to prepare the blue, red, yellow, and green three-component thermochromic dyes. According to the laws of subtractive color mixing, multicolor-tunable thermochromic dyes are obtained by color matching of red, yellow, and blue dyes to span multiple shades. Biomass thermochromic dyes are adopted to fabricate temperature-controlled linen fabrics by the vacuum impregnation process. Temperature-controlled linen fabrics can change color reversibly between the original color and achromatic color. The color-changing occurs due to the ring opening and closing of leuco dyes triggered by the solid-to-liquid transition of solvent. The phase transition temperature of the thermochromic dyes absorbed on the linen fabric is 46 ℃. As the temperature increases, the contact angle of temperature-controlled linen fabrics decreases from 129° to 29°, resulting in a change from hydrophobic to hydrophilic with 49 J g−1 of thermal energy stored. The linen fabrics exhibit temperature-controlled changes in color, surface wettability, strength, and thermal insulation. This eco-friendly method with biomass thermochromic dyes for the preparation of color-changing linen fabrics provides a new approach, which is contributing to the development of cellulose-based smart color-changing textiles.