Dual Clay Nanobrick Wall Thin Films with High Oxygen Barrier at High Humidity

Thin polymer-based coatings with high oxygen barrier at elevated humidity are needed for the protection of food and organic electronic devices. Polyelectrolyte-based thin films (deposited via layer-by-layer assembly) perform well at ambient humidity, but their performance typically dwindles as humidity increases due to their hydrophilic nature. Retention of their high barrier can be achieved through the addition of chemical crosslinkers or the introduction of inorganic platelets that create a nanobrick wall structure. In this study, a nanobrick wall barrier prepared with two types of clay, with a thickness less than 200 nm, is shown to reduce the oxygen transmission rate (OTR) of 179 mu m polyethylene terephthalate to less than 0.016 cm3 m-2 day-1 atm-1. At 90% relative humidity (RH), a quadlayer barrier consisting of polyethylenimine, boehmite clay, poly(acrylic acid), and vermiculite clay maintains nearly 90% of its barrier performance at 0% RH (OTR = 0.019 cm3 m-2 day-1 atm-1). This study demonstrates the potential of dual clay thin film nanocomposites to protect various consumer goods at high humidity. Various nanobrick wall thin films, deposited using layer-by-layer assembly, are subjected to oxygen transmission rate testing at low and high humidity to determine the influence of ordering and thickness on oxygen transmission rate. By increasing the number of clay layers at a given thickness the oxygen barrier retention can be significantly improved.image