Synthesis of strong and highly stretchable, electrically conductive hydrogel with multiple stimuli responsive shape memory behavior

Abstract A highly tough and conductive hydrogel with good shape memory behavior was facilely prepared via constructing the catechol-Fe3+ interactions in the poly(vinyl alcohol) (PVA) hydrogel matrix. The hydrophobic 5,5,6,6-tetrahydroxy-3,3,3,3-tetramethyl-1,1-spirobisindane (TTSBI) was introduced to provide the catechol ligands for Fe3+. The fabricated TTSBI-2@Fe3+-12 nanocomposite hydrogel performed great toughness (9.23 MJ/m3), large tensile strength (3.25 MPa) and high extensibility (752%). The distinguished mechanical performance of the composite hydrogel was contributed by the synergy of nanophase separation structure formed by TTSBI in PVA matrix, strong hydrogen bonding interaction between PVA and TTSBI, and metal coordination interaction of catechol-Fe3+. The introduced Fe3+ also imparted good conductivity to the hydrogel. Moreover, the mechanical and conductive properties of the composite hydrogel could be flexibly regulated by the pH value. The conductive hydrogel showed excellent sensitivity to stretching, bending, twist, and compression. In addition, the hydrogel exhibited multiple-stimuli responsive shape memory behaviors. This work offers a hierarchical self-assembly strategy to fabricate functional hydrogel with tailored mechanical, conductive properties and shape memory behavior for a series of promising applications such as flexible wearable electronics and intelligent actuators.