Transparent, Ultrathin Super Gas Barrier Thin Films Prepared via Layer-by-Layer Assembly

摘要

A variety of functional, water-based coatings can be produced using layer-by-layer (LbL) assembly. LbL coatings are currently being evaluated for their antimicrobial, electrically conductive,3 and gas barrier behaviors, among other things. These films are created by alternately exposing a substrate to positively- and negatively-charged molecules or particles, as shown in Figure 1. In this study, steps 1 C 4 are continuously repeated until the desired number of "quadlayers"(or pairs of a cationic-anionic polymer bilayer followed by a cationic polymer- anionic clay bilayer) is achieved. Each individual layer may be 1 C 100+ nm thick. The ability to control film composition down to the nm-level and process under ambient conditions are two key advantages of this deposition technique. In the present study, clay was deposited one layer at a time in conjunction with polymeric mortar to create a nano-brick wall, shown in Figure 1(b), with an oxygen transmission rate (OTR) below the detection limit of commercial instrumentation (0.005 cc/m~2day). This level of oxygen barrier is unprecedented for clay-filled polymer composites, which have been widely studied for reducing oxygen permeability in polymer films.