Synthesis and characterization of nanocomposites from functionalized graphene

Abstract

The graphene study has become the most interested topic owing to its exceptional properties. Graphene brings dramatic changes in the possessions of composites, when it is used even at very low concentration. Though, the heterogeneous distribution of graphene in the matrix is its main drawback to be used as filler in the polymer composites. The strong intermolecular forces of graphene result in agglomeration of graphene in the host the polymer matrix. The surface of graphene is functionalized by different functional groups to reduce the π-π stacking to prevent the agglomeration of graphene. The main objective of this work was to develop an easy method for synthesizing the graphenebased polymer nanocomposites. To get the graphene-based nanocomposites, first graphene was exfoliated by using liquid-phase exfoliation in different organic solvents. Picric acid was also used as a surfactant. The addition of picric acid has doubled the concentration in most of solvents tested. Moreover, graphene oxide was produced by using Hummers’ methods, modified Hummers’ method and Brodie method. The results indicate that modified Hummers’ method is the best one among the three methods. In next step polyaniline was grafted on few layer graphene (FLG), and polyaniline grafted fewlayer graphene (PANI-g-FLG) samples were then blended with polyetherimide. The addition of PANI-g-FLG introduced the conductive behavior in the insulative polymer. The maximum dielectric constant (3.72 × 105) and AC conductivity (5.91 × 10−2 S⋅cm−1) were achieved at 1.5 wt.% of the FLG concentration. Moreover, polyaniline grafted few layer graphene was also added in polyvinyl alcohol (PVA) by solution blending method. The tensile strength was enhanced 62 % for the composites as compared to pure PVA. The dielectric constant was enhanced from 3.29 of pure PVA to 5.14 × 1004 (at 1000Hz) for nanocomposites having 0.5 wt.% FLG loading. Similarly, AC conductivity increased from 9.05 × 10−9 for pure PVA to 2.17 × 10−2 S⋅cm−1 (at 1000Hz) for composites having 0.5 wt.% FLG loading. The PANI-g-FLG was also combined with polystyrene to prepare nanocomposites with varying concentration of FLG (0 to 2 wt.%). The tensile strength was doubled for the composites as compared to pure polystyrene. The graphene oxide produced by modified Hummers’ method was further functionalized and incorporated into the diglycidyl ether of bisphenol A to prepare nanocomposites. The concentration of PANI-g-GO were varied from 0 to 2.5 wt.% in the nanocomposites. The tensile strength was enhanced 60% for the composites as compared to pure diglycidyl ether of bisphenol A. The dielectric constant was improved from 1 to 8 and AC conductivity increased from 1.05 × 10−8 S⋅cm−1 for pure to 6.15 × 10−8 S⋅cm−1 (at 1000Hz) for composites having 2.5 wt.% FLG loading. These results provide a possibility of using flexible nanocomposites as a dielectric material to be applied for energy storage devices such as embedded capacitors.