Thermal- and pH-responsive triple-shape memory hydrogel based on a single reversible switch.

Here we provide a novel method for fabricating a pH- and thermal-responsive triple-shape memory hydrogel based on a single reversible switch phase. A high-density quadruple hydrogen-bonding ureido-pyrimidinone (UPy) system was introduced into the hydrogel network, which can occur to varied degrees of dissociation under different pH and temperature conditions. Different degrees of dissociation and reassociation can be viewed as different subsets of memory elements to freeze and unfreeze the temporary shapes. Although this class of hydrogels contains only a single transition phase, they feature a large dissociative differential in response to varied external stimuli to provide multiple windows for programming different temporary shapes.