TEMPERATURE-DEPENDENT CONDUCTIVITY IN GRAPHENE-POLYMER NANOCOMPOSITE: MOLECULAR MODELING APPROACH
Loading...
Author(s)
Vasudevan, Vaibhav S.
Advisor(s)
Editor(s)
Collections
Supplementary to:
Permanent Link
Abstract
Graphene-polymer nanocomposites utilize the exceptional electrical, thermal, and mechanical properties of graphene and have attracted tremendous attention for many industry applications. However, many criteria relating to the structure-property relationship still need to be further explored before commercialization and widespread adoption. For instance, the temperature-dependent morphologies of graphene-polymer nanocomposites and their result on electrical conductivity have not been thoroughly scrutinized.
Therefore, for this thesis, we investigated a graphene-polymer nanocomposite system consisting of graphene, xanthan gum (XG), Pluronic F127 (F127), and cetyltrimethylammonium bromide (CTAB) using molecular dynamics (MD) simulation method to analyze structural transitions between 298 K and 373 K which are observed through electrical conductivity measurements in experiment. To accomplish this, we prepared nanocomposite model systems containing a mixture of graphene, XG, F127, and CTAB models. The equilibrated structures were obtained at 298 K and 373 K after an annealing procedure. To analyze the resultant structures, we developed a method to characterize the graphene graphene contacts within the model systems using the pair correlation function of carbon(graphene) carbon(graphene) pairs at 298 K and 373 K. We found that the number of carbon atoms involved in the three different types of graphene graphene contacts within the system such as edge-to-edge, edge-to-plane, and plane-to-plane contacts are noticeably greater at 373 K after annealing than at 298 K. In order to identify which components are responsible for this structural transition, we analyzed the molecular displacement of each component in the nanocomposite systems using pair correlation functions of the carbon(graphene) carbon(molecule) pairs and mean squared displacements of the molecules. It turned out that the movement of CTAB and XG within the system plays a crucial role in the structural transitions during the annealing procedure. Finally, by estimating the electrical conductivity of graphene-polymer nanocomposite model systems through DFT-based non-equilibrium Green function (DFT-NEGF) calculations, we found that the estimated electrical conductivity significantly increased after the annealing procedure.
Sponsor
Date
2021-07-28
Extent
Resource Type
Text
Resource Subtype
Thesis