Electrospinning and multilayer modification to construct NH2/EPSP-modified polyacrylonitrile nanofiber films for humidity regulation

Photoresponsive materials may be used to improve the humidity of a microenvironment, thus improving the comfort of people occupying that space. In this work, by constructing a synergistic layer (amino groups) and a regulating layer (spiropyran compounds) on the surface of polyacrylonitrile (PAN) electrospun membranes, we successfully developed fiber materials with excellent mechanical stability that can reversibly regulate the humidity of the microenvironment. Spiropyran molecules can undergo photoisomerization (reversible polar-nonpolar structure interconversion) by conversion of ultraviolet/visible light. The wettability and microenvironment humidity can be controlled bidirectionally under different light sources. More importantly, the amino groups on the fiber surface can assist the ring-opened merocyanine in absorbing water molecule, thus playing a synergistic role. Moreover, changing the electrospinning voltages can help regulate the porosity of the fiber materials, which can change wettability and the humidity range regulation. The energy change of spiropyran before and after water absorption was obtained by density functional theory calculations, and it is further proven that the synergistic layer can promote the ability of humidity regulation.