Morphological investigation of Graphene Oxide/ Polyacrylamide super-elastic nanocomposite by a solution polymerization process with enhanced rheological property and thermal conductivity

A series of Graphene Oxide/ Polyacrylamide (GO/PAM) super-elastic nanocomposites with different amounts of Graphene Oxide Nanosheets (GONSs) (۰.۵, ۱, ۱.۵, and ۲ wt. %) were synthesized using an in-situ polymerization in an aqueous medium in this paper. To this end, we proposed a method for obtaining super-elastic nanocomposites with a high dispersion of GONSs in the PAM chains as well as in a rapid synthesis. Fine adaptability, powerful inner interaction between embedded GONSs into the PAM chains, and remarkable enhancement of mechanical and thermal properties of synthesized GO/PAM super-elastic nanocomposites can be considered as the unique characteristics of this synthesis method in a short time. In this study, GONSs were prepared by a modified Hummer's procedure at ambient temperature. Fourier Transform Infrared (FT-IR) spectroscopy, X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), thermo-Gravimetric Analysis (TGA) and DifferentialThermal Analysis (DTA) were employed to characterize the internal network structure of GONSs, PAM, and GO/PAM nanocomposites. XRD investigation indicated the increase of the interlayer spacing of GONSs. The exfoliation and dispersion of GONSs in the PAM matrix were studied by XRD and FESEM. The formation of oxygen-including groups on the surface of GONSs and hydrogen linking between GONSs and PAM was confirmed by FT-IR spectra and DTA. Atomic Force Microscopy (AFM) was used to evaluate the thickness of the synthesized GONSs that was measured to be about ۶.۸۵ nm. Ultraviolet-Visible (UV/vis) spectroscopy illustrated the high percent of oxidation with more oxygen-including groups on the GONSs basal surface. Raman spectroscopy was also utilized to determine the induced disorder degree in the synthesized graphene oxide and distinguish the number of its layers. Thermal properties curves of GO/PAM nanocomposites represented an improvement trend in degradation temperature and a remaining amount up to GO-loaded (۱.۵ wt. %). The addition of GONSs also showed the significant improvement of viscoelastic behavior in PAM chains. The highest storage modulus (G'; ۶.۴۲ MPa) and loss modulus (G"; ۰.۹۸ MPa) are related to GO/PAM nanocomposite with ۱.۵ wt. % GO-loading. Based on the empirical result, the GONSs could remarkably enhance the thermal conductivity of PAM which was measured to be about ۰.۴۹ W.m-۱.K-۱. Thermal conductivity of GO۱.۵/PAM nanocomposite was about ۰.۹ W.m-۱.K-۱ that showed ۸۴ % increase compared to the PAM.

Keywords:

GONSs , GO/PAM Nanocomposite , Rheological property , Solution Polymerization , Thermal conductivity