Characterization of A Am/MBA hydrogels prepared by radiation induced polymerization

In this research the network structure of polyacrylamide hydrogels prepared by gamma radiation-induced polymerization has been investigated. The average molecular weight between cross-link junctions ‾Mc and effective cross-link density of hydrogels were calculated from swelling data as well as shear modulus data. The mechanical tests showed that by increasing the amount of the cross linker methylenebisacrylamide (MBA) into hydrogels, the value of shear modulus G and cross-link density νe increased, but the average molecular weight between cross-link junctions ‾Mc, decreased. The ‾Mc and the effective cross-link density νe obtained from the mechanical characterization were significantly different than the values obtained from swelling experiments. These differences were attributed to the uncertainty on the value of the χ parameter used in the Flory-Rehner equations. The results have shown that simple compression analyses can be used for the determination of νe without any need of polymer-solvent interaction parameter for its calculations from the swelling analysis. (Author)