Radiation synthesis and characterization of hydrogels composed of poly(vinyl alcohol) and acrylamide mixtures

Hydrogels based on various compositions of poly( vinyl alcohol) (PVA) and acrylamide ( AM) monomer were produced under the effect of gamma-irradiation. The hydrogels were characterized by IR spectroscopy and thermogravimetric analysis (TGA). In addition, the effect of temperature and pH on the swelling behavior was studied. It was proved that the composition of the final product corresponds to the initial composition of the preparing solutions. The IR spectroscopic analysis showed the formation of interpenetrating networks and the existence of hydrogen bonding. The thermal study and the calculation of activation energy of the thermal decomposition reaction of PVA/AM hydrogels showed that the PVA/AM hydrogels, over the studied compositions, possessed lower thermal stability than the individual polyacrylamide (PAM) hydrogel. The kinetic studies of swelling in water showed that the neat PAM and PVA/AM hydrogels reached equilibrium after six hours, while neat PVA polymer hydrogel reached equilibrium after three hours. However, PVA/AM hydrogels show swelling in water less than neat PAM and higher than neat PVA. The results showed that PVA/AM hydrogels displayed a temperature responsive character within the temperature range 40 - 50 degrees C, and showed shrinkage in swelling in the pH range 5 - 7 depending on composition. This behavior was not clear in the case of hydrogels composed of binary mixtures of PVA and AM components.