Polymer-Graphene Oxide Nanobrick Wall Gas Separation Membranes

Thin films of graphene oxide (GO) and branched polyethylenimine (PEI) were prepared by alternately depositing thin layers from water onto a PET film.   This layer-by-layer (LbL) deposition process creates sub-micron films with a nanobrick wall architecture.  After depositing ten PEI-GO bilayers (BL) on 175 mm PET, the resulting construction exhibits an oxygen permeability of 3.9 x 10^-17 cm³ cm/cm² s Pa.  When the 91 nm thick transparent film permeability is decoupled from the total construction, it is shown to exhibit an oxygen permeability below 7 x 10^-20 cm³ cm/cm² s Pa.  This level of oxygen barrier is unprecedented for a polymer nanocomposite and is believed to be due to the nanobrick wall structure comprised of completely exfoliated GO bricks in polymeric mortar.  This thin film is a true foil replacement technology, useful for flexible electronics and microwaveable food packaging.  This same film has an undetectable CO₂ transmission rate, while only reducing the H₂ transmission rate of PET by one order of magnitude.  When taken together, this PEI-GO thin film has an H₂/CO₂ selectivity greater than 380.  If it can be assumed that OTR and CO₂TR are comparable for this film, it has a selectivity greater than 10,000.  There is tremendous potential for these types of multilayer thin films to serve as size selective separation membranes for a variety of gases/vapors.