Biocomposites based on starch with multi-functionalized graphene oxide: Effect of graft composition and concentration

The current global scenario has a great impact on the development of new bio-based materials due to the vital advantages that are helpful in replacing synthetic and hazardous materials. In this study, biocomposites (BC) of cassava starch/grafts of multi-functionalized graphene oxide were synthesized by solvent casting. To improve their interface compatibility, graphene oxide (GO) was grafted with fructose, microcellulose and/or starch. The multi-functionalization of GO (grafts) was determined by Fourier transform infrared and Raman spectroscopy. The results confirm the covalent bond between GO and organic molecules, with a grafting average percentage of 45% by weight. Subsequently, the effects of the concentrations and composition of grafts on surface morphology (SEM) showed that the use of multi-functionalized GO with organic molecules improves the compatibility and graft-matrix interaction, preventing agglomeration, and it favors the formation of well-dispersed BC. The thermogravimetric analysis (TGA) revealed significant improvement in the thermal stability of BC with grafts at 3%. The mechanical properties of BC showed tensile strength values were four (4) times higher as compared with those of CS matrix. The elongation at break values was also directly related to the concentration and type of grafts. The functionalization of GO with organic molecules allows to obtain BC with good thermomechanical properties, reducing the load of GO, which increases their applications. This knowledge can be used to the development of homogeneous and high-quality BC through the modification of the GO structure as a fundamental step to improve graft-matrix interactions.