With a highly ordered nanobrick wall structure, polyelectrolyte-montmorillonite (MMT) clay multilayer nanocoatings can dramatically reduce the oxygen transmission rate (OTR) of polymer films used in various packaging applications (e.g., polyethylene terephthalate (PET) and oriented polypropylene (OPP)) by several orders of magnitude. In an effort to produce high oxygen barrier with fewer deposition steps, pH of the MMT aqueous suspension was reduced. In a polyethylenimine (PEI)/poly(acrylic acid) (PAA)/PEI/MMT quadlayer system, the reduced pH of MMT causes the preceding PEI layer to be more charged, which results in more clay to be deposited per layer. A compromise between high polymer diffusion (high pH) and high clay deposition (low pH) was found at pH 6, where the best oxygen barrier is achieved. A 179 µm thick PET substrate, coated with only three PEI/PAA/PEI/MMT quadlayers (44 nm thick), exhibits an undetectable oxygen transmission rate (&lt; 0.005 cm3/(m2 day atm)). The calculated oxygen permeability is orders of magnitude below SiOx and metal thin films (&lt;5 ×10-22 cm3 cm/(cm2 s Pa)). This reduced number of layers necessary for high gas barrier potentially makes these transparent, multilayer thin films interesting for commercial packaging applications.

Balancing polyelectrolyte diffusion and clay deposition for high gas barrier

254th National Meeting (2017)

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