Highly Efficient “Composite Barrier Wall” Consisting of Concentrated Graphene Oxide Nanosheets and Impermeable Crystalline Structure for Poly(lactic acid) Nanocomposite Films

Poly­(lactic acid) (PLA), a promising sustainable packaging material, suffers from intrinsic poor gas barrier performance partly due to its innate defect of relatively low crystallization rate. In the present study, taking advantage of the excellent impermeability and heterogeneous nucleating ability of graphene oxide nanosheets (GONSs), the crystalline structure of PLA nanocomposite film was manipulated using processing techniques. We revealed that GONSs were the α-nucleating agent for PLA, inducing typical spherulite morphology. More interestingly, two-dimensional small-angle scattering characterization confirmed that GONSs were preferentially dispersed in the amorphous phase between PLA spherulites, achieving a concentrated GONS region. As a consequence, the “composite barrier wall” consisting of concentrated GONSs and impermeable PLA lamellae gave rise to O<sub>2</sub> permeability of PLA nanocomposite film at a GONS loading of 1.0 wt % as low as 0.211 × 10<sup>–14</sup> cm<sup>3</sup> cm cm<sup>–2</sup> s<sup>–1</sup> Pa<sup>–1</sup>, reduced by ∼89.9% relative to neat amorphous PLA film. These results presented here afford new insight into the contribution of GONSs and their induced crystalline structure to the significantly enhanced barrier performance, which may also open up a promising avenue for design and fabrication of high-barrier polymer packaging materials.