Starch/graphene hydrogels via click chemistry with relevant electrical and antibacterial properties

[Display omitted] •Starch based hydrogels were prepared by aqueous Diels-Alder reaction.•Conductive hydrogel was obtained with graphene and Salvia extracts.•The rheology and microstructure were influenced by the cross-linker amount.•Nanocomposites showed antibacterial activity and increased mechanical properties.•The electrical conductivity of the hydrogel nanocomposites was increased. Starch-based hydrogels were performed by Diels-Alder cross-linking reactions between furan-modified starch and a water soluble bismaleimide, with improving conducting properties by using graphene layers as active nanofillers. The characterization results demonstrated that the Diels-Alder reaction and the corresponding conditions for the hydrogel formation were appropriate. The effect of increasing the furan/maleimide ratio on the architecture of the hydrogels and on the morphological, rheological and swelling properties were thoroughly evaluated. Effective network structure was obtained by increasing the cross-linker content leading to decreasing pore size and increasing storage modulus value of the final material. It was shown that the swelling behavior of hydrogels was mainly governed by the hydrophilic character of bismaleimide. Graphene nanosheets were added for the synthesis of nanocomposite hydrogel and it was characterized in terms of rheological properties, electrical conductivity and antimicrobial activity. The nanocomposite hydrogel presented enhanced mechanical performance, antimicrobial activity and increased conductivity values, up to a decade, indicating that conductive and active hydrogels could be satisfactory obtained, for a large range of potential applications such as biomed.