Zinc ion uniquely induced triple shape memory effect of dipole-dipole reinforced ultra-high strength hydrogels

In this study, we demonstrate that dipole-dipole interaction can be employed to not only tremendously enhance the mechanical properties of hydrogel, but also impart the gel to an amazing ability to memorize two temporary shapes. Cross-linked hydrogels synthesized by copolymerization of acrylonitrile, a dipole-dipole containing monomer and hydrophilic comonomer are shown to exhibit triple shape memory (SM) triggered by the dynamic association and dissociation of dipole-dipole pairing between cynao groups uniquely responding to zinc ion species and concentration. This approach contributes to design and fabrication of novel SM hydrogels in a distinct way from conventional SM materials.