Water‐Induced Densification of Electrospun <scp>PVP</scp> / <scp>PU</scp> Membrane for Transparent and Anti‐Fogging Applications

ABSTRACT Transparent fiber membranes with high optical transparency and mechanical flexibility are challenging to achieve due to light scattering from the porosity of electrospun structures. In this study, a composite membrane was fabricated using electrospinning of polyurethane (PU) and polyvinylpyrrolidone (PVP) fibers, followed by water‐immersion and air‐drying to densify the membrane. The water solubility of PVP and elasticity of the PU matrix facilitated capillary‐driven structural rearrangement, reducing inter‐fiber voids and maintaining the fibrous skeleton integrity, resulting in a dense, quasi‐continuous membrane. The treated membrane demonstrated 84.4% visible light transmittance, 21.7% haze, reduced total reflectance to 7.8%, and diffuse reflectance to 6.7%, providing optical clarity and anti‐glare properties by suppressing specular reflection. Additionally, the surface's intrinsic hydrophilicity conferred excellent anti‐fogging performance. The membrane also exhibited outstanding mechanical deformability, transitioning to ductile fracture behavior with an elongation at break of approximately 25.49%, attributed to uniform stress distribution and strong intermolecular hydrogen bonding. This study introduces a simple, environmentally friendly approach for producing transparent, low‐reflective, and mechanically robust fibrous membranes, with potential applications in flexible optoelectronics and optical protection devices.