▎ 摘　　要

Graphene oxide (GO) nanosheets featuring high surface activity and large planar dimension may function as robust nanointerfaces in biocomposites, contributing to simultaneous promotion of mechanical and gas barrier properties. Here, a solution-processed, additive-free approach to immobilize few-layer GO nanosheets on starch granule surfaces (GO@starch) by hydrogen bonding is demonstrated. This approach enabled a straightforward pathway to remove the intersheet van der Waals forces (pi-pi stacking) that generally cause reaggregation and poor dispersion of GO in polymer matrices. Incorporation of GO@starch into poly (lactic acid) (PLA) allowed an interesting structure with few-layer nanosheets firmly immobilized at the PLA-starch interfaces. Inheriting the high aspect ratio and surface energy of GO, GO@starch distinctly strengthened the interfacial interactions with PLA, albeit present at ultralow GO concentrations (up to 0.03 wt %), facilitating the dispersion of GO@starch and nucleation of PLA. The morphological regulation rendered composite films with an impressive combination of high thermal stability, mechanical strength and oxygen resistance. A substantial increase of 280% in tensile strength (58.2 MPa) and a prominent decline of 82% in oxygen permeation coefficient (4.0 cm(3) mm cm(-2) day(-1) atm(-1)) were achieved in the composites loaded with 30 wt % GO@starch in comparison with the counterpart. The cost-performance ratio for the nanostructured biocomposites was excellent even compared to the established packaging materials. The multiscale morphological regulation of sheet-like nanofillers by controlled exfoliation and immobilization of GO on microsized starch particle surfaces, the simplicity of manufacturing, together with the versatility of the engineered composites should make our strategy broadly applicable to other material combinations.