title: Nanomechanical Behavior of High Gas Barrier Multilayer Thin Films.
abstract: Nanoindentation and nanoscratch experiments were performed on thin multilayer films manufactured using the layer-by-layer (LbL) assembly technique. These films are known to exhibit high gas barrier, but little is known about their durability, which is an important feature for various packaging applications (e.g., food and electronics). Films were prepared from bilayer and quadlayer sequences, with varying thickness and composition. In an effort to evaluate multilayer thin film surface and mechanical properties, and their resistance to failure and wear, a comprehensive range of experiments were conducted: low and high load indentation, low and high load scratch. Some of the thin films were found to have exceptional mechanical behavior and exhibit excellent scratch resistance. Specifically, nanobrick wall structures, comprising montmorillonite (MMT) clay and polyethylenimine (PEI) bilayers, are the most durable coatings. PEI/MMT films exhibit high hardness, large elastic modulus, high elastic recovery, low friction, low scratch depth, and a smooth surface. When combined with the low oxygen permeability and high optical transmission of these thin films, these excellent mechanical properties make them good candidates for hard coating surface-sensitive substrates, where polymers are required to sustain long-term surface aesthetics and quality.
authors.affiliation: Department of Mechanical Engineering, Texas A&M University , College Station, Texas 77843-3123, United States.
authors.forename: Mohammad
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: Shahla
authors.initials: S
authors.lastname: Chowdhury
authors.affiliation: Department of Materials Science and Engineering, Texas A&M University , College Station, Texas 77843-3003, 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.
authors.forename: Ping
authors.initials: P
authors.lastname: Tzeng
authors.affiliation: Department of Mechanical Engineering, Texas A&M University , College Station, Texas 77843-3123, United States.|Department of Materials Science and Engineering, Texas A&M University , College Station, Texas 77843-3003, United States.
authors.forename: Jaime C
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.initials: AA
authors.lastname: Polycarpou
keywords: gas barrier; layer-by-layer deposition; multilayer thin films; nanoindentation; nanoscratch