title: Influence of Graphene Reduction and Polymer Cross-Linking on Improving the Interfacial Properties of Multilayer Thin Films.
abstract: Graphene is a versatile composite reinforcement candidate due to its strong mechanical, tunable electrical and optical properties, and chemical stability. However, one drawback is the weak interfacial bonding, which results in weak adhesion to substrates. This could be overcome by adding polymer layers to have stronger adherence to the substrate and between graphene sheets. These multilayer thin films were found to have lower resistance to lateral scratch forces when compared to other reinforcements such as polymer/clay nanocomposites. Two additional processing steps are suggested to improve the scratch resistance of these films: graphene reduction and polymer cross-linking. Graphene/polymer nanocomposites consisting of polyvinylamine (PVAm) and graphene oxide (GO) were fabricated using the layer-by-layer assembly (LbL) technique. The reduced elastic modulus and hardness of PVAm/GO films were measured using nanoindentation. Reducing GO enhances mechanical properties by 60-70% while polymer cross-linking maintains this enhancement. Both graphene reduction and polymer cross-linking show significant improvement to scratch resistance. Particularly, polymer cross-linking leads to films with higher elastic recovery, 50% lower adhesive and plowing friction coefficient, 140 and 50% higher adhesive and shear strength values, respectively, and lower material pileup and scratch width/depth.
authors.affiliation: Department of Mechanical Engineering, Texas A&M University , College Station, Texas 77843-3123, United States.
authors.forename: Mohammad
authors.identifier: http://orcid.org/0000-0003-4169-1525
authors.initials: M
authors.lastname: Humood
authors.affiliation: Department of Mechanical Engineering, Texas A&M University , College Station, Texas 77843-3123, United States.
authors.forename: Shuang
authors.initials: S
authors.lastname: Qin
authors.affiliation: Department of Mechanical Engineering, Texas A&M University , College Station, Texas 77843-3123, United States.
authors.forename: Yixuan
authors.initials: Y
authors.lastname: Song
authors.affiliation: Department of Mechanical Engineering, Texas A&M University , College Station, Texas 77843-3123, United States.|Department of Mechanical Engineering, Khalifa University , Abu Dhabi 127788, UAE.
authors.forename: Kyriaki
authors.initials: K
authors.lastname: Polychronopoulou
authors.affiliation: Department of Mechanical Engineering, Texas A&M University , College Station, Texas 77843-3123, United States.
authors.forename: Youfeng
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Mechanical Engineering, Texas A&M University , College Station, Texas 77843-3123, United States.
authors.forename: Jaime C
authors.identifier: http://orcid.org/0000-0001-5241-9741
authors.initials: JC
authors.lastname: Grunlan
authors.affiliation: Department of Mechanical Engineering, Texas A&M University , College Station, Texas 77843-3123, United States.
authors.forename: Andreas A
authors.identifier: http://orcid.org/0000-0002-8178-3988
authors.initials: AA
authors.lastname: Polycarpou
keywords: delamination; graphene; layer-by-layer-assembly; nanoindentation; scratch