Facile preparation of conductive composite hydrogels based on sodium alginate and graphite

Conductive composite hydrogels based on sodium alginate (SA) and graphite were obtained by a facile method of dispersing homogeneously conductive graphite into SA hydrogel matrix formed by in situ release of Ca2+ from Ca-EDTA, which avoids the multistep reactions and tedious purification compared to the previous work. The SA/graphite composite hydrogels exhibit reticulate and layer-type structure. The equilibrium swelling ratio of the composite hydrogels decreased with higher graphite content, although the swelling kinetics with various graphite contents was similar. The conductivity of the composite hydrogels could be tuned by adjusting f ([Ca2+]/[COO− in alginate]) and the content of graphite, which reaches up to 10−3 S/cm.