Poly(N-vinyl-2-pyrrolidone) hydrogels produced by Fenton reaction

'Instantaneous' hydrogels from poly(N-vinyl-2-pyrrolidone) aqueous solutions can be produced using Fenton reagents, i.e., a redox reaction. A firm hydrogel is formed within 5-10 s, with a total gelling time below 8 min. Hydroxyl radical is recognized as the possible high energy intermediate responsible for the crosslinking reactions. The major variables of the process (PVP, H2O2 and Fe2+ initial concentrations, as well as pH) were examined and shown to operate within a rather narrow working window. The process efficiency and the properties of the hydrogel formed are discussed and compared with other methods of hydrogel production.