Modeling electronic properties of polymeric-based composite thin films

Abstract

Thin films of polymer-based composites have been widely studied in recent decades due to their multiple applications. This is because they are materials that exhibit the physicochemical properties of both the polymer composite and the nanomaterial from which the composite is made (electrical, mechanical and thermal). For this reason, modeling these properties of CPCs is a fundamental part of predicting their behavior as a material. In this thesis, an ab initio method is developed to model the anisotropic conductivity of a stretched CPC made of a polymeric matrix of polyvinyl alcohol (PVA) mixed with single-walled carbon nanotubes (SWCNTs). These quantities are obtained by a combination of density functional theory calculations, non-equilibrium Green's functions based methods and an affine deformation geometric statistical statistical model. In this way, we provide a qualitative and semi-quantitative description of the measured anisotropic conductivity of PVA/SWCNT CPCs. The success of this model demonstrates that the conductivity of CPCs is determined by (1) the connectivity of the SWCNTs network within the polymer matrix, (2) the resistance to intertubular conductance hopping, (3) the concentration of SWCNTs in the sample, and (4) the amount of stretching and the concomitant orientational order parameter of the SWCNTs in the composite. The developed model can potentially be applied to obtain CPCs with desired anisotropic conductivity based on ballistic conductive nanomaterials, i.e., SWCNTs, and different polymeric matrices.