Unique Morphology in Polylactide/Graphene Oxide Nanocomposites

Polylactide (PLA)/graphene oxide (GO) nanocomposites with different GO loadings were prepared by solution blending using tetrahydrofuran (THF) as solvent. The morphologies of the nanocomposites in the cast films and in subsequently isothermally crystallized samples were investigated separately. According to polarized optical microscopy images of the composites after isothermal crystallization, it was deduced that GO had nucleation effects on the crystallization of PLA and led to the size of spherulites decreasing and the number of spherulites increasing. However, by virtue of SEM, unique microsphere morphologies were found in the cast films of the PLA/GO composites. It was found that the features of this kind of microsphere were not influenced by the compositions but by the evaporation rate of the solvent during the preparation of the cast films. A faster evaporation rate of solvent resulted in smaller size of the microspheres. Based on DSC and FTIR results, it was proposed that the forming of this kind of microsphere was related to hydrogen bonds being formed between PLA and GO. The unique microsphere morphology is suggested to provide a new method to prepare PLA microsphere-based scaffolds.