Improvement in Barrier Properties Using a Large Lateral Size of Exfoliated Graphene Oxide

The gas barrier properties of polymers can be improved by reducing gas diffusivity and solubility by using graphene oxide (GO) of various lateral sizes (~3, ~25, ~45 µm). By using GO, the gas diffusion path of the polymer was effectively increased. To reduce the solubility, alkylated GO (AGO) was synthesized by an SN2 reaction between octyl amine and GO. The hydrophobicity of AGO was confirmed through contact angle measurements, and octylamine on the AGO surface was identified by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis. When GO and AGO with comparatively large lateral size (~45 µm) were homogeneously dispersed in polyvinyl alcohol (PVA) and polyvinylidene chloride (PVDC), respectively, the oxygen transmission rates (OTR) of resulting PVA/GO and PVDC/AGO composite films were significantly reduced. The OTR of PVA/GO composite film reduced from 1.9 × 100 to 5.0 × 10−2 cm3/m2·day as compared to neat PVA; whereas, the OTR of PVDC/AGO composite film reduced from 1.2 × 100 to 6.8 × 10−1 cm3/m2·day. In addition, the water vapor transmission rate (WVTR) of the PVDC/AGO composite film remarkably decreased from 1.4 g/m2·day (neat PVDC) to ∼5.5·10−1 g/m2·day, where the lateral size of AGO was insignificant. The WVTR results of PVDC/AGO composite films are in contrast to those for PVA/GO composite films, which did not demonstrate any improvement in WVTR with the addition of GO. Based on the experimental results, it was determined that oxygen permeability and water vapor permeability are more affected by diffusivity and solubility, respectively.