Sponge-like Cryogels from Liquid-Liquid Phase Separation: Structure, Porosity, and Diffusional Gel Properties

Macroporous gels find application in several scientificfields,ranging from art restoration to wastewater filtration or cell entrapment.In this work, two-component sponge-like cryogels are challenged toassess their cleaning performances and to investigate how pores sizeand connectivity affect physico-chemical properties. The gels wereobtained through a freeze-thaw process, exploiting a spontaneouspolymer-polymer phase-separation occurring in the pre-gel solution.During the freezing step, a highly hydrolyzed polyvinyl alcohol (H-PVA)forms the hydrogel walls. The secondary components, namely a partiallyhydrolyzed polyvinyl alcohol (L-PVA) or polyvinyl pyrrolidone (PVP),act as modular porogens, being partially extracted during gel washing.H-PVA/L-PVA and H-PVA/PVP mixtures were studied by confocal laserscanning microscopy to unveil sols and gels morphology at the micron-scale,while small angle X-ray scattering was used to get insights aboutcharacteristic dimensions at the nanoscale. The gelation mechanismwas investigated through rheology measurements, and the characteristicexponents were compared to De Gennes' scaling laws gatheredfrom percolation. In the field of art conservation, these sponge-likegels are ideal systems for the cleaning of artistic painted surfaces.Their interconnected pores allow the diffusion of cleaning fluidsat the painted interface, facilitating dirt uptake and/or detachment.This study uncovered a direct relationship linking a gel'scleaning performance to its apparent tortuosity. These findings canpave the way to fine-tuning systems with enhanced cleaning abilities,not restricted to the restoration of irreplaceable priceless worksof art, but with possible application in diverse research fields.