From starch to polylactide and nano-graphene oxide: fully starch derived high performance composites

Abstract

A delicate closed-loop strategy for valorization of starch to value-added products was developed. Carbon sheets, formed of carbon spheres, were obtained by microwave-assisted hydrothermal degradation of starch and then further transformed into nano-sized graphene oxide (nGO, 20 × 30 nm²) under oxygen-rich acidic conditions. The synthesized nGO exhibited self-assembly in solution. Furthermore, nGO strongly attached to the surface of starch granules by hydrogen bonding (nGO@starch, 0.1 wt%) and allowed easy and highly efficient interfacial engineering in PLA/starch composites. After combining with polylactide (PLA), the composites could incorporate up to 30 wt% nGO@starch, while retaining excellent properties. nGO was capable of facilitating PLA crystallization in the composites by providing a number of nucleation sites. Moreover, the interfacial adhesion between PLA and starch was significantly improved by nGO. Though its content was extremely low, nGO improved the mechanical and barrier properties and thermal stability of the PLA/starch composites. The results demonstrate a facile route to value-added starch-derived nGO and further to fully starch derived high performance PLA/starch biocomposites.