Layer-by-Layer (LbL) assembled polymer-clay nanobrick wall thin films are transparent and flexible super oxygen barriers. Alternating deposition of cationic polymers and anionic clay platelets creates extreme tortuosity. Lower oxygen transmission rate (OTR) with fewer deposition cycles has recently been achieved with shorter deposition time and adjusting the pH of clay suspensions. In this study, sodium chloride was introduced into an aqueous montmorillonite (MMT) clay suspension at pH 6.5, where the amphoteric edge sites of MMT have a neutral net charge. The salt effectively shields the charge of neighboring MMT platelets, which results in better clay coverage. An 8 bilayer (BL) polyethyleneimine (PEI)/MMT film (55 nm thick), assembled in the presence of 5 mmol NaCl, exhibits an order of magnitude improvement in oxygen barrier relative to its no-salt counterpart at pH 6.5 (and three orders of magnitude better than the 175 micron thick PET substrate). This “salty clay” strategy provides a faster and more efficient method to fabricate nanobrick wall polyelectrolyte oxygen barriers.

Edge charge neutralization of clay for improved nanocoating gas barrier

255th National Meeting (2018)

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