High gas barrier of clay/graphene oxide/chitosan multilayer nanocoatings at high humidity

Improving the barrier properties of bio-based polymers is very desirable for food packaging applications. With this in mind, a gas barrier thin film comprised of graphene oxide (GO), montmorillonite (MMT) clay, and chitosan (CH) was prepared using layer-by-layer assembly. A 120 nm thick CH/MMT/CH/GO quadlayer nanocoating reduces the oxygen permeability of a 179 μm polyethylene terephthalate sheet from 17.6×10⁻¹⁶ to 0.21×10⁻¹⁶ cm³ cm cm⁻² s⁻¹ Pa⁻¹ at 0 % RH, and from 13.4×10⁻¹⁶ to 0.42×10⁻¹⁶ cm³ cm cm⁻² s⁻¹ Pa⁻¹ at 90 % RH. This two orders of magnitude reduction in permeability in both dry and high humid conditions is caused by the hybrid multilayer structure, with a high loading of oriented, densely packed nanoplatelets. This study demonstrates the potential of combining different anionic nanoplatelets in the assembled nanocoatings to improve the gas barrier performance of chitosan at high humidity.