(722e) Ultrathin and Transparent Nanobrick Wall Super Gas Barrier Assemblies

Ultrathin and
transparent nanobrick wall super gas barrier assemblies*

Thin films of natural, sodium montmorillonite clay and weak
polyelectrolytes were prepared by alternately dipping a PET substrate into four
different dilute aqueous mixtures (polyethylenimine, poly(acrylic
acid), polyethylenimine, and montmorillonite clay).   After depositing four of these quadlayers
(QL), the resulting transparent film exhibits an oxygen transmission rate at or
below the detection limit of commercial instrumentation (≤ 0.005 cm³
m^-2 day^-1).  This
level of oxygen barrier, which is unprecedented for a clay-filled polymer
composite, is believed to be due to a nanobrick wall microstructure comprised
of completely exfoliated clay bricks in polymeric mortar and clay layer spacing
on the order of tens of nanometers.  This
4 QL film, with a thickness of only 51 nm and optical transparency of 95%, represents
a true foil replacement technology, useful for flexible electronic displays, microwaveable
food containers, and pharmaceutical packaging.

* Submitted to AIChE 08A12.