Effects of molecular mass of polymer on mechanical properties of clay/poly (ethylene oxide) blend hydrogels, and comparison between them and clay/sodium polyacrylate blend hydrogels

In this study, we examined mechanical properties of clay/polyethylene oxide (PEO) hydrogels as functions of the molecular mass of PEO and the composition. The hydrogels using ultra-high molecular mass PEOs higher than a few millions possessed very high extension (1000~2000%) and higher fracture stress in comparison with the gels using lower molecular mass PEOs. The mechanical strength was significantly affected by the composition, e.g., the moduli increased with increasing clay concentrations, whereas they decreased with the increase of the PEO concentration. The tensile properties between the clay/PEO gel and the clay/sodium polyacrylate (PAAS) gel with almost the same molecular masses were compared, so that their moduli had almost the same values, whereas the tensile strength for the former was much lower than that for the latter. Synchrotron small-angle X-ray scattering and quartz crystal microbalance analyses have revealed that the tensile behavior is attributed to weaker interactions between clay and PEO in comparison with those between clay and PAAS.