Molecularweight effects on tensile properties of blend hydrogels composed of clay and polymers

Hydrogels with mechanical toughness have attracted the attention of many researchers but still the mechanism remains poorly understood. In this study, we investigated molecularweight effects on the tensile properties for two kinds of blend hydrogels such as clay/sodium polyacrylate and clay/polyacrylamide, which were prepared by simple mixing, in order to clarify key factors of the mechanical toughness. The elastic modulus of the former hydrogel was much higher than that of the latter, while the latter extensibility was much higher than that of the former. It has been found that use of polymers with molecularweights higher than a few millions is necessary to obtain high extensibility for the blend hydrogels. It has been clarified from this study that all of the following three factors, (i) use of high molecularweight polymers, (ii) dispersion of clay particles and (iii) favorable interactions of clay and polymers are necessary to be fulfilled for fabrication of the blend hydrogels with mechanical toughness. (C) 2016 Elsevier Ltd. All rights reserved.