Development of photochromic poly(azobenzene)/PVDF fibers by wet spinning for intelligent textile engineering

Compared to azobenzene (AB) mono-molecule, the as-synthesized AB polymer showed better photochromic ability and chemical resistance. An intelligent fiber with photochromic properties can be successfully developed with the as-synthesized AB polymer and polyvinylidene fluoride (PVDF) via a facile wet spinning process. The doping of AB polymer in intelligent fiber showed little effect on intrinsic properties of PVDF fiber but significantly altered the surface performances like aesthetics, UV sensing and shielding. The intelligent fiber could reversibly change the color from pale yellow to orange red under UV irradiation, conferring a potential to be used as a flexible UV indicator. As a functional embroidery thread on fabric, the photochromic PVDF fiber displayed stable photochromic responses, reversible optical contrast and good photo-coloration kinetics, greatly improving the appearance and functionality of the substrate fabric. Moreover, the fabric knitted with this photochromic fiber could offer UV shielding property verified with the high ultraviolet protection factor. Furthermore, the functional fiber had good resistance to different solvents, thus, it exhibited qualities to be used under harsher conditions. Compared with the extensive research of spiropyrans (SPs) and spirooxazines (SOs) in color-changing textile, this study would be a complementary research for the application of azobenzenes (ABs) in intelligent textiles.