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Transparent Polyelectrolyte Complex Thin Films with Ultralow Oxygen Transmission Rate

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journal contribution
posted on 27.08.2018 by Ryan J. Smith, Carolyn T. Long, Jaime C. Grunlan
Limiting oxygen permeation through plastic films is important for extending the shelf life of food and flexible electronic devices. Polyelectrolyte complex (PEC) thin films can be used to reduce small molecule diffusion through commodity plastic films. PEC thin films are frequently applied using layer-by-layer assembly, which often requires many processing cycles to deposit a film with desired thickness. An aqueous solution of poly­(diallydimethylammonium chloride) and poly­(acrylic acid) can be deposited in a single-step to quickly fabricate a high-oxygen barrier thin film. These films have an ionically bonded network that forms after polyelectrolyte deposition and exposure to buffer. Increasing buffer concentration and adding salt increases film cohesion and improves transparency by reducing surface roughness. When deposited onto a 178 μm poly­(ethylene terephthalate) film, a ∼1.9 μm thick PEC coating imparts a 2 orders of magnitude reduction in oxygen transmission rate. Achieving this level of gas barrier with a single thin coating layer creates numerous opportunities for the protection of sensitive food, pharmaceuticals, and electronics.