A high strength hydrogel with quadruple-shape memory under the ambient condition

It is worth looking forward to manufacturing a shape memory hydrogel (SMH) with good mechanical properties for practical applications in a simple and rapid manner. In this study, the one-pot method has been proposed to prepare a quadruple shape memory hydrogel (PAA-CS, poly(acrylic acid)-chitosan). The PAA-CS hydrogel obtained by mixing acrylic acid (AA), chitosan (CS), initiator, and cross-linker at 60 °C shows excellent function of shape memory and recovery less than 20 s. Moreover, its maximum deformation can reach to 100%. Scanning electron microscopy (SEM) showed that PAA-CS hydrogels would form new cross-linked networks in NaOH, NaCl, and FeCl3, and these new networks can trigger quadruple shape memory. In addition, the tensile and compressive strength tests showed the PAA-CS hydrogel possesses outstanding mechanical properties. Its excellent property has enormous potential in applications where multi-shape changes responding to different stimuli are required.