Effect of functionalized graphene oxide on gelation and scaling law of alginate in aqueous solution

Abstract

A facile one-pot method was designed and used to synthesize alginate (SA) noncovalently functionalized amino-graphene oxide, A-aGO, which possesses an excellent dispersibility in water. Subsequently, A-aGO was added to an aqueous solution of alginate and the gelation behavior of A-aGO/SA in water was studied by rheology when calcium chloride (CaCl2) was used as a physical crosslinking agent. The presence of A-aGO promoted the sol–gel transition of alginate, where the critical gel concentration of CaCl2 (cg) decreased and the critical gel strength Sg increased with increasing A-aGO content, even though the critical relaxation exponent n was almost constant. A schematic diagram was proposed, which is able to describe the change in the junctions of gel network with increasing A-aGO content, and further interpreted the rheological scaling law at the gel point. In the stable gel state, the plateau modulus Ge of A-aGO/SA hydrogels at a fixed concentration of Ca2+ ions depended on A-aGO content according to a parabola equation, Ge=831.1+11740.4w−6448.6w2, where w is the weight percentage of A-aGO relative to alginate. The FESEM images further verified a porous microstructure of A-aGO/SA gels, and the pore size decreased and the pore density increased with A-aGO due to the increased junction density at a higher A-aGO content.