(738b) Toughness, Self-Healing, and Network Formation in Pristine Graphene/Polyacrylamide Gels
Enhancement of toughness in nanomaterial-based hydrogels is a critical metric for the various engineering applications of these gels. Here pristine graphene/polyacrylamide (PAM) hydrogels are synthesized via in-situ polymerization of acrylamide monomer in PAM-stabilized graphene dispersions. In-situ polymerization leads to the uniform dispersion of the graphene sheets in the hydrogel. The pristine graphene sheets interact with the elastic chains of the hydrogel through physisorption and permit gelation in the absence of any chemical cross-linker. This study represents the first report of pristine graphene as a physical cross-linker in a hydrogel. The properties of the graphene-polymer hydrogel are characterized by viscoelastic measurements and compressive tests, revealing an increase in the storage modulus and toughness of the hydrogels compared to the chemically cross-linked PAM analogs. The physically cross-linked graphene hydrogels also exhibit excellent self healing properties. These graphene/PAM hydrogels serve as effective precursors for aerogels which become electrically conductive when graphene sheets form an interconnected network inside the network of the aerogel skeleton. Monomer infusion into the aerogel scaffold leads to the formation of ultralow percolation threshold graphene composites. The backfilling of the additives creates a conductive nanocomposite with a very low filler loading, without any network disruption.