Engineering ultraporous and highly stable Polyacrylonitrile/Poly(vinyl alcohol) sponges with high water absorption capacity

Abstract

Ultraporous sponges capable of absorbing large quantities of water-based liquids are of great interest in various fields of research. In this study, ultraporous polyacrylonitrile/poly(vinyl alcohol) (PAN/PVA) sponges with exceptional water absorption capacity─up to 16000% of their dry weight─were produced through a four-stage process: electrospinning, short fiber suspension creation, freeze-drying, and PVA cross-linking with different maleic anhydride (MA) concentrations. Characterization by electron microscopy and X-ray microscopy revealed a porosity of 90% and an average fiber thickness of 0.4 μm. Mechanical tests demonstrate that the wet sponge is more compliant and experiences greater elongation than the dry sponge, with failure occurring below 20% strain in dry samples and above 40% when wet. In situ tensile testing in a micro-CT scanner and digital volume correlation analysis reveal significant morphological changes during stretching, including strain localization and microstructural variations. These findings provide insights into the mechanical behavior of the PAN/PVA sponges and identify regions that are prone to fracture. By the combination of electrospun PAN and PVA fibers in a stabilized ultraporous architecture, this work introduces a practical and efficient strategy for producing lightweight hydrophilic sponges for applications in water management, biomedical devices, and tissue engineering.