Enhancing the radiative heating performance of down fibers by layer-by-layer self-assembly

Filling materials and fabrics with radiative heating properties have promising applications on personal thermal management and demonstrate a series of advantages in reducing the energy consumption and improving the convenience and lightweight of warm clothing. However, the fluffiness of the down fibers is usually decreased after the functional modifications and coating, resulting in the deterioration of warmth retention and appearance. Although the warmth retention of the down fibers can be improved by decoration of Zr (Ⅳ), it is not a good way to address the problems originated from the low-loading and poor washability of Zr (Ⅳ) due to the weak interactions between the down fibers and Zr (Ⅳ). Herein, we report a novel and facile layer-by-layer (LBL) self-assembly strategy to fabricate the Zr (Ⅳ) modified down fibers with high Zr (Ⅳ) loading, excellent radiative heating performance and washability. The surface temperature of Zr (Ⅳ) modified down fibers is increased by 3.75 °C after being exposed to the infrared radiation source, which exceeds the state-of-the-art chemical modified down fibers. More importantly, the radiative heating performance of Zr (Ⅳ) modified down fibers deteriorates less than 5% after 8 wash cycles, exhibiting good washability. The excellent radiative heating performance is attributed to the robust coordinate bonds between phytic acid and zirconium ions. In addition, the prepared down fibers have natural fluffy velvet flowers and high fluffiness without any broken fibers owing to the moderate LBL self-assembly process. This work paves the way for the low-damage functional modifications of the down fibers and other protein materials.