Novel nanoporous superabsorbent hydrogel based on poly(acrylic acid) grafted onto salep: Synthesis and swelling behavior

Hydrogels of poly(acrylic acid) grafted onto salep with excellent water absorption and water retention abilities under neutral conditions were successfully synthesized for the first time and employed for different applications. The effect of reaction variables to achieve maximum swelling capacity was investigated. In our procedure, ammonium persulfate (APS) as a water-soluble initiator and methylenebisacrylamide (MBA) as a suitable crosslinking agent were used and the best synthesis conditions described. The structure of the final product was confirmed by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy SEM and TGA analysis and a mechanism for superabsorbent hydrogel formation was also suggested. The study of the surface morphology of hydrogels using SEM showed a highly nanoporous and cellular structure for the sample obtained under optimized condition. Furthermore, several factors which influence the water uptake of hydrogels, such as pH of water, sensitivity to salt solutions and solvent mixtures were examined.