Hydrogen-bonded multilayer thin films are very stretchable, but their gas barrier properties are modest compared to more traditional ionically bonded assemblies. In an effort to improve the gas barrier of poly(ethylene oxide) (PEO)-poly(acrylic acid) (PAA) multilayer films without sacrificing stretchability, montmorillonite (MMT) clay platelets were combined with PAA and alternately deposited with PEO. A ten-bilayer PEO/PAA+MMT film (432 nm thick), deposited on a 1 mm PU substrate, resulted in a 54× reduction in oxygen transmission rate after exposure to a 20% strain. This system is the best combination of stretchability and gas barrier ever reported.

The growth dynamics for metallic filaments in conductive-bridge resistive-switching random access memory (CBRAM) are studied using the kinetic Monte Carlo (KMC) method. The physical process at the atomistic level is revealed in explaining the experimental observation that filament growth can originate at either the cathode or the anode. The statistical nature of the filament growth is best shown by the random topography of dendrite-like conductive paths obtained. Critical material properties, such as charged-particle mobility in the switching layer of a solid electrolyte or a dielectric, are mapped to KMC model parameters through activation energy, etc. The accuracy of the simulator is established by the good agreement between the simulated forming time and the measured data.

of their colloidal stability, mechanical strength, high specific surface area, and thermal stability, [2][3][4][5][6] which have been used to produce transparent paper, biodegradable packaging, complex aerogels, and as the reinforcing phase in composites. [2,4,7,8] Despite all of its beneficial properties, cellulose exhibits poor flame resistance and gas barrier properties. [9,10] Improved barrier, mechanical, and flame resistant properties have been reported when montmorillonite clay (MMT) is used as a reinforcing agent in cellulose-based films. [11][12][13] The performance of polymer-clay barrier films is determined primarily by the clay characteristics (e.g., aspect ratio and density) and dispersion properties (i.e., clay exfoliation and orientation). For cellulose/clay composites, different methods to increase the interaction between clay and cellulose have been reported, including TEMPO-oxidation and by adding poly(vinyl alcohol) or chitosan (CH) as a compatibilizer. [14][15][16] Recently, cationic CNF with a quaternary ammonium functionality has been reported. [17] It was shown that the ionic interaction between the cationic CNF and MMT results in better mechanical properties of the composite, but further improvement is limited due to the formation of nanovoids as well as relatively low clay loading. [12,18] Layer-by-layer (LbL) assembly is a nanocoating technique that has been used to construct functional thin films for gas barrier and gas separation coatings, [19,20] energy storage and conversion, [21,22] drug delivery, [23] and adhesives. [24] By alternately depositing oppositely charged polyelectrolytes and/or clay platelets onto a charged substrate, thin films are assembled with high clay concentration and alignment. [25] In the present study, multilayer films consisting of anionic vermiculite (VMT) clay, with a high aspect ratio (≈2000), and cationic cellulose nanofibrils were investigated. This unique combination of highly aligned VMT platelets and cellulose nanofibrils forms a nanobrick wall structure with high transparency, excellent oxygen barrier, and fire resistance (superior to any other cellulose-based film previously reported). A 20 bilayer (BL) CNF/VMT nanocoating, with a thickness of 136 nm, exhibits a low oxygen transmission rate (OTR) of 0.013 cc (m 2 day atm) -1 . With only 2 BL of CNF/VMT, the melting of flexible polyurethane (PU) foam is prevented when exposed to a butane torch flame. These nanocoatings also exhibit high elastic modulus Cellulose nanofibrils (CNF) are abundant in the fiber cell walls of many plants and are considered a nearly inexhaustible resource. With the goal of improving the flame resistance and gas barrier properties of cellulose-based films, cationic CNF are assembled with anionic vermiculite (VMT) clay using the layer-by-layer deposition process. The highly aligned VMT nanoplatelets, together with cellulose nanofibrils, form a nanobrick wall structure that exhibits high optical transparency, flame resistance, super oxygen barrier, and high modulus. A 20 CNF/VMT...

A thin film coating with tailorable thickness and clay concentration was prepared by solution casting an aqueous slurry containing poly(vinyl alcohol) (PVOH) and montmorillonite (MMT) clay. The anisotropic clay platelets have excellent alignment due to self-orientation during drying, which results in good transparency and oxygen barrier. A 50 wt % clay coating, with a thickness around 4 μm and visible light transmission of 58%, improves the oxygen barrier of a 179 μm poly(ethylene terephthalate) (PET) substrate by more than 3 orders of magnitude. This PVOH/MMT composite thin film also has good thermal stability and mechanical properties. This simple coating procedure could be used for a variety of packaging applications that use plastic film (e.g., food, pharmaceutical, and electronics).