Graphene enhances the shape memory of poly (acrylamide-co-acrylic acid) grafted on graphene

Acrylamide and acrylic acid are grafted on graphene by free-radical polymerization to produce a series of graphene-poly(acrylamide-co-acrylic acid) hybrid materials with different contents of graphene. The materials demonstrate shape memory effect and self-healing ability when the content of graphene is in the range of 10%-30% even though poly(acrylamide-co-acrylic acid) itself had poor shape memory ability. The permanent shape of the materials can be recovered well after 20 cycles of cut and self-healing. The result is attributed to the hard-soft design that can combine nonreversible "cross-link" by grafting copolymer on graphene and reversible "cross-link" utilizing the "zipper effect" of poly(acrylamide-co-acrylic acid) to form or dissociate the hydrogen-bond network stimulated by external heating.