Hydrogen bonded polymer complex thin films for highly stretchable gas barriers

Abstract

Clay-containing polyelectrolyte complexes have been investigated as simple and effective gas barrier coatings for a variety of substrates. Some applications for barrier coatings, such as stretchable electronics, require films that exhibit high extensibility as well as low oxygen transmission rate. This combination of properties is difficult to achieve, as barrier tends to go hand-in-hand with film density. In this work, a stretchable thin film with low oxygen transmission rate (OTR) was prepared through the addition of montmorillonite (MMT) clay into a hydrogen bonded complex of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA). Interpolymer hydrogen bonding and MMT clay distribution were found to improve with an increasing ratio of PEO to PAA in the complex, leading to the creation of a highly stretchable coating with a high gas barrier. This elastomeric system, deposited in three steps on 760 μm thick natural rubber, reduces the OTR by two orders of magnitude with a thickness of 1.8 μm. This film maintains a >90% reduction in OTR even after it is subjected to 50% strain. This is believed to be the first gas barrier coating deposited as a buffer-cured, hydrogen bonded polymer complex.