Abstract:

Objective Compared with chemical color, photonic crystals (PCs) structural color is controlled by external stimuli, transforming stimuli signals to facilitate visible color change. Solvent-response PCs structural colors are easy to achieve and hence are popularly used with convenience, and hence are extensively studied. However, most of the solvent-responsive PCs structural colors are constructed on flat substrates and based on hydrogel material. There are few studies on constructing solvent-responsive structural colors on the flexible fabrics, because it is more difficult to obtain uniform and stable structural color coatings on the rough and deformable surface. In this paper, polystyrene-methyl methacrylate-acrylamide (P(St-MMA-AM))microspheres containing hydrophilic chains were synthesized to construct structural colors with solvent-responsive on fabrics, aiming for creation of smart responsive structural color textiles.

Method P (St-MMA-AM) microspheres containing hydrophilic chain were synthesized by soap-free emulsion polymerization using styrene (St), methyl methacrylate (MMA) and acrylamide (AM) as monomers. The influence of monomer ratio on particle size of the microspheres was studied. P(St-MMA-AM) microspheres were atomized and deposited on polyester woven fabric to form structural color with solvent responsiveness. The color properties and solvent response properties of different solvents of the structural colored fabrics were studied. The color fastness and physical properties of the structural colored fabric were also studied.

Results P(St-MMA-AM) polymer microspheres with hydrophilic chains were successfully synthesized through soap-free emulsion polymerization. By changing the mass ratios of the monomers, P(St-MMA-AM) microspheres with different particle sizes of 392.7, 384.1, 358.6, 344.6 nm, and 322.4 nm were obtained, accordingly five different structural colors of pink, green, blue, light blue and purple were achieved on the fabrics by atomized deposition of these P(St-MMA-AM) microspheres. When wetted with water or ethanol, these structural colored fabrics could change their colors to fuchsia, yellow-green, dark green, cobalt blue, and dark blue, respectively, within 1-2 s. Once the solvent was evaporated, the five structural colors would revert to their original colors. The wavelengths corresponding to the maximum reflectance (λ_max) of the five structural colors on the fabric were 590, 510, 460, 430 nm, and 410 nm respectively. After being wetted by water, the λ_max of the five structural colors shifted to 390, 530, 490, 450 nm, and 440 nm, which could return to their initial values after the water evaporated, demonstrating excellent solvent-reversible response performance. Both single-color and multi-color patterned structural colored fabrics exhibited solvent responsiveness, showing potential for the preparation of patterned fabrics with special responsiveness. There was no obvious color change of the structural colored fabrics before and after rubbing, except for the decreasing of the maximum reflectance λ_max by only 0.22% compared to that before rubbing. After washing, the colors of the structural colored fabrics remained almost the same as they were before, and the maximum reflectance decreased by only 0.33%, indicating good rubbing and washing color fastness, which could be attributed to the fixation of the microspheres on the fabric by the polyacrylate binder. Compared with the original fabric, the wrinkle recovery performance of the structural colored fabric remained unchanged, and there was a slight decrease in softness and air permeability, demonstrating that the physical properties of structural colored fabrics were slightly influenced.

Conclusion In this study, P(St-MMA-AM) microspheres with five different particle sizes were successfully prepared by adjusting the monomer mass ratio, which formed five different structural colors i.e. pink, green, blue, light blue and purple on polyester fabrics through atomized deposition. The structural color fabrics showed fast solvent-responsive performance, changing color within 1-2 s after wetting by water and ethanol. After solvent evaporation, the five structural colors restored to their original colors, showing the excellent solvent reversible response performance. The structural colored fabrics also had good rubbing and washing colorfastness. The physical properties of the structural colored fabrics were slightly influenced compared with the original fabrics. This study provides an experimental basis for the development of smart responsive structural color textiles.

Key words: structural color, photonic crystal, solvent response, polymer microsphere, intelligent responsive textile