Letter pubs.acs.org/Langmuir
Thick Growing Multilayer Nanobrick Wall Thin Films: Super Gas Barrier with Very Few Layers Tyler Guin,† Michelle Krecker,‡ David Austin Hagen,‡ and Jaime C. Grunlan*,‡ †
Department of Chemical Engineering and ‡Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843, United States ABSTRACT: Recent work with multilayer nanocoatings composed of polyelectrolytes and clay has demonstrated the ability to prepare super gas barrier layers from water that rival inorganic CVD-based films (e.g., SiOx). In an effort to reduce the number of layers required to achieve a very low oxygen transmission rate (OTR (1 μm) to be produced with few layers. This simple modification to the layer-by-layer assembly process facilitates the achievement of desirable properties such as an oxygen barrier with fewer bilayers.
INTRODUCTION Thin films that are impermeable to oxygen are a key component in a wide variety of applications, such as food and microelectronics packaging.1 Highly oxygen-sensitive food packaging (e.g., for coffee and high-fat snacks) requires an oxygen transmission rate (OTR) of less than 1 cc/m2·day·atm,2 while flexible organic light-emitting devices require an OTR below 10−5 cc/m2· day·atm.3 Monolithic inorganic oxide thin films, such as SiOx, are commonly used as transparent high-barrier layers but are frequently unable to meet these requirements.4 These inorganic layers are prone to defect formation, poor substrate adhesion, and failure upon flexure, and they require expensive ultrahigh vacuum processing conditions.5 Many alternative gas barrier layers have been explored, such as polymer−inorganic nanocomposites.6 In particular, polymer−clay nanocomposite films produced via layer-by-layer (LbL) assembly have shown promise due to their high transparency, ambient processing conditions, and extremely high oxygen barrier (
