Preparation and formation mechanism of colorful photonic crystals on rough yarns

The environmentally friendly dyeing of textiles combining regular photonic crystals (PCs) has shown remarkable promise for application. However, the surface is rough and undulating and contains many harnesses due to fullcurved structure of yarns. All these factors increase the difficulty of assembling colloidal microspheres into regular PCs on yarns. Therefore, relevant studies on the preparation methods and fundamental theories for constructing bionic structural colors on conventional flexible yarns are few. This study contains two main parts: first, regular PC-based yarns were produced by the dip coating method with poly (styrene-butyl acrylate-methacrylate) (P(St-BA-MAA)) as building block. Specifically, the softness and surface flatness of acrylic yarns were improved using silicone-modified polymer solution and cationic acrylate solution. The results indicated that assembling of PC with vivid structural color was easier when the base color of yarns was black and the concentration of P(St-BA-MAA) colloidal microspheres was about 60 wt%. Second, the self-assembling mechanism of microspheres on acrylic yarns was further studied by untwisting and slicing. The results showed that colloidal microspheres would fill the surfaces and voids of the outer fibers of acrylic yarns to form regular PCs, and they would also enter the inner fibers of yarns by capillary forces. However, the structure of yarns was tight inside and loose outside due to twisting and other reasons. Therefore, the colloidal microspheres had more difficulty entering the fibers on the inner side of the yarn to form an ordered PC structure when the fibers were closer to the yarn axis. The PC-based colored yarn also remained bright after the rubbing test. The color phase of the structured colored yarns based on PC could be adjusted as well by regulating the particle size and the observation angle. The prepared structured colored yarns were woven into fabrics, which were named yarnstructure colored fabrics. This research provides theoretical support and technical guidance for the preparation and practical application of flexible structured colored yarns based on PC.