Mechanical, thermal and swelling properties of poly(acrylic acid)–graphene oxide composite hydrogels

Graphene oxide (GO) is added into poly(acrylic acid) (PAA) hydrogels to modify their mechanical and thermal properties. The original PAA hydrogels, which are commonly crosslinked by N,N-methylenebisacrylamide (BIS), generally exhibit pronounced weakness and brittleness. When GO was added into the BIS-gel, the GO–BIS-gels become very tough and exhibited fairly good strength. The mechanical and thermal properties of GO–BIS-gels vary greatly by changing GO or BIS content. As for the swelling behaviors of the hydrogels, they are found to be still sensitive to pH. However, the BIS-gels have a higher equilibrium swelling ratio and swell faster than that of corresponding GO–BIS-gels. In addition, the deswelling ratio decreases with the increase of GO content. The cross-linking of GO with PAA is the main factor for these phenomenon. Thus, the content of GO and BIS can be adjusted for preparing hydrogels with different properties for a wide range of applications.