No abstract

In this work, we report the synthesis of graphene oxide (GO) nanohybrids with starch, fructose, and micro-cellulose molecules by sonication in an aqueous medium at 90 °C and a short reaction time (30 min). The final product was washed with solvents to extract the nanohybrids and separate them from the organic molecules not grafted onto the GO surface. Nanohybrids were chemically characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy and analyzed by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD). These results indicate that the ultrasound energy promoted a chemical reaction between GO and the organic molecules in a short time (30 min). The chemical characterization of these nanohybrids confirms their covalent bond, obtaining a grafting percentage above 40% the weight in these nanohybrids. This hybridization creates nanometric and millimetric nanohybrid particles. In addition, the grafted organic molecules can be crystallized on GO films. Interference in the ultrasound waves of starch hybrids is due to the increase in viscosity, leading to a partial hybridization of GO with starch.

The current global scenario has a great impact on the development of new biobased 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 multifunctionalization 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.