Thin films prepared via layer-by-layer (LbL) assembly, using positively charged chitosan (CH) in the presence of tris buffer and negatively charged vermiculite clay (VMT), dramatically increase the oxygen barrier of polyethylene terephthalate (PET) film and reduce the flammability of polystyrene sheet. At only eight bilayers (BL), the films reach an impressive thickness of 3.7 μm and a dry mass of 1.2 mg/cm<sup>2</sup>, which is among the highest reported for a layer-by-layer (LbL) system. A variety of film thicknesses can be achieved by adjusting the tris concentration of the cationic solution and its rinse. Buffering these solutions with only 50 mM of tris increased the thickness of the films by an order of magnitude. The oxygen transmission rate (OTR) of coated PET was 0.009 cc/m2•day•atm, with only six bilayers (BL) added, and was below the commercial detection limit (0.005 cc/m2•day•atm) with eight BL added. Polystyrene sheeting of 0.125 inch thickness with only 2 BL added was self-extinguishing, and 8 BL added prevented ignition entirely.

Thick growing multilayer thin film with high gas barrier and fire resistance

249th National Meeting (2015)

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