Thermo-/chemo-responsive shape memory/change effect in a hydrogel and its composites

Water/moisture-content dependant behavior in a commercial hydrogel [poly(acrylamide-co-acrylic acid)] is systematically investigated. As shown, at lower water/moisture contents, the hydrogel has the thermo-responsive and moisture-induced shape memory effect (SME); while at higher water/moisture contents, the hydrogel has the rubber-like mechano-responsive and water-induced shape change effect (SCE). Furthermore, it is revealed that on the one hand, programming can be realized by means of deforming at high temperatures (above the glass transition temperature) or dehydration after pre-deforming rubber-like hydrogel; on the other hand, hydrogel can be used as the elastic matrix in a hybrid for tailored SME. Typical potential applications utilizing combined thermo-responsive and water-responsive SCE/SME are proposed.