Realization of ultra-high barrier to water vapor by 3D-interconnection of super-hydrophobic graphene layers in polylactide films

Abstract

Inferior water barrier performance has always been a major deficiency of polylactide (PLA) that is in practice difficult to overcome owing to the existence of plentiful hydrophilic ester bonds in the main chain. Here, we propose an architecture of super-hydrophobic 3D-networks in PLA, where interconnected graphene oxide grafted octadecylamine (GOgODA) nanosheets are able to effectively suppress dissolution and diffusion of water molecules into the PLA matrix. Prior to the employment of the special technology “decoration of building block for vapor barrier – post-molding assembly”, uniform-sized PLA microspheres and super-hydrophobic GOgODA were simultaneously prepared. Perfect GOgODA networks were successfully realized within transparent nanocomposite PLA films and obvious enhancement of the water barrier was prominently achieved. Specifically, a remarkable decrease of almost 6.5 times in water permeability coefficient was observed for the nanocomposite films containing a very small volume (0.268 vol%) of GOgODA (1.43 × 10⁻¹⁴ g cm cm⁻² s⁻¹ Pa⁻¹) compared with pure PLA films (9.28 × 10⁻¹⁴ g cm cm⁻² s⁻¹ Pa⁻¹). This prominent amelioration was derived from the ordered dispersion of well-extended GOgODA nanosheets, which concentrate selectively at the interface of PLA regions and are arranged exactly perpendicular to the permeating pathway of water molecules. This methodology provides a facile and effective way to advance the functions and properties of PLA.