Network structure studies on γ-irradiated collagen-PVP superabsorbent hydrogels

Collagen-polyvinylpyrrolidone (PVP) superabsorbent hydrogels were synthesized by γ- irradiation in the absence of oxygen, using high molecular weight PVP and acidic collagen Type I. Sol-gel analysis and swelling experiments were performed in order to determine the gel fraction, network parameters, the yield of cross-linking, respectively scission, as well as to establish the diffusion characteristics of water. Rheological experiments and characterization of the chemical structure before and after irradiation were conducted in order to evaluate the gel character and its stability upon irradiation. The relationship between these parameters and radiation dose was also established. Gel fraction reached up to 90%, and the p0/q0 ratio (degradation vs. cross-linking ratio) shows a negligible degradation process. The collagen-PVP hydrogels present swelling in the range 1000-2000%, the diffusion exponent (n) was found to be between 0.59 and 0.68. The network parameters as the molecular weights between two successive cross−links (Mc), the cross-linking density (ϑe) and the mesh size (ξ) are ranged between 3.39-8.08×104g·mol-1, 1.24-2.95×10-5mol·cm-3, respectively 75-134 nm.