Aspect Ratio Control of Layered Double Hydroxide Nanosheets and Their Application for High Oxygen Barrier Coating in Flexible Food Packaging.

We report a method to rationally control the aspect ratio of layered double hydroxide for use as a barrier coating for food packaging films. The reconstruction of a MgAl-layered double oxide (LDO) in concentrated aqueous glycine solutions produces dispersions of MgAl-LDH nanosheets. The nanosheet thickness decreases and diameter increases with increasing reconstruction time from 16 to 96 h. We observe a limiting nanosheet aspect ratio of ca. 336 ± 170. These MgAl-LDH nanosheets can be dispersed in PVA to give a water-based dispersion that can be used to coat flexible polymeric films. Oxygen transmission rate (OTR) of a PET film decreases when the thickness of the dried coated layer increases, an OTR of <0.005 mL·m·day is observed for a coating with thickness of 1175 ± 101 nm.