Synthesis and Characterization of Graphene and Graphene Based Polymer Composites

Abstract

Thin films composites of Poly (ethylene oxide) - Graphene Oxide were fabricated with and without Lithium salts by solvent cast method. With different contents of salt polymer -GO complexes, the ionic conductivity of these composites was examined at various temperatures. The Arrhenius conductance plots were utilized to determine the impacts of temperature and Graphene Oxide concentration. It is revealed that the conductance of the system considerably enhances with the incorporation of salts in pure PEO. The conductance has enhanced approximately 1000 times due to the addition of Graphene oxide in comparison with that of pure PEO. On measuring the activation energies for all the three systems it was seen that the system with pure PEO showed greater activation energy while it exhibit considerable decline due to the incorporation of LiClO4 and LiCl salts in the system and more decrease on adding Graphene Oxide. The addition of GO in PEO decreases crystallinity and the amorphous region increases local mobility of polymer chain which in turn results in decreased activation energy. XRD study reveals that amorphicity in the composite increasing with increasing GO contents. SEM analysis demonstrate even distribution of GO in polymer matrix. The mechanical investigations demonstrate that the Young modulus and tensile strength remarkably increase with increasing GO contents. The rheological analysis reveals decrease in apparent viscosity and complex viscosity while increase in shear thinning and Storage modulus. The thermal stability studies reveal that mixing of GO has improved a little bit the thermal stability of the films. The dispersion behavior of Graphene oxide (GO) prepared by modified Hummer’s method was also studied in ten different solvents namely Water, Tetrahydrofuran(THF), Dimethyl Formamide(DMF), Ethylene Glycol, xxviii Acetone, Pyridine, 2-Propanol, Methanol, Ethanol, and Dimethyl Sulfoxide (DMSO). The effect of sonication and addition of surfactant (Sodium Cholate) on dispersion behavior was also investigated. Homogeneous dispersions were found in all freshly prepared GO solutions but they were short lived. The dispersions were then left as such for three weeks and after three weeks they were observed again. It was found that stable dispersions were left only in some solvents like Water, THF, DMF, Ethylene Glycol and Pyridine. Finally in a separate set of experiment we treated the GO solutions in all these solvents with surfactant (Sodium Cholate) and sonication (400 Hrs) to see the dispersion behavior. It was observed that stable dispersion remained only in few solvents like Water, DMF, Ethylene Glycol and Pyridine. These were most stable and showed no sedimentation or settling down of GO even after three weeks. These solvents are easily available and can be effectively used for dispersion formation and further processing of graphene.