Designing Scalable Anisotropically Conductive Thin Films Using Hot Drawing of Poly(vinyl alcohol)/Single-Walled Carbon Nanotube Composites

The production of industrially scalable conductive polymer-based composites (CPCs), with tailored physicochemical properties, such as anisotropic conductivity, has proved a formidable challenge in nanoscience and nanotechnology. This is because the final performance of such CPCs dramatically depends on the distribution and type of polymer matrix, the degree of spatial ordering, and the material’s percolation threshold. By adjusting the concentration of single-walled carbon nanotubes (SWCNTs) within a hot-drawn poly(vinyl alcohol) (PVA) composite, we show that a 10-fold increase in the CPC’s conductivity and a four-fold increase in its anisotropy may be obtained. Using a combination of Raman spectroscopy, density functional theory (DFT), and nonequilibrium Green’s function (NEGF)-based methods, we develop a general ab initio model, which describes qualitatively and semiquantitatively the measured conductivity of our PVA/SWCNT CPCs. The success of this model shows that the CPC’s conductivity is determined by (1) the connectivity of the SWCNT network within the polymer matrix, (2) the hopping resistance to intertube conductance, (3) the concentration of SWCNTs in the sample, and (4) the amount of stretching and concomitant orientational order parameter of the SWCNTs in the composite. Our combined experimental and theoretical approach provides a means for designing CPCs with given anisotropic conductivities based on SWCNTs within different polymer matrices and should prove highly relevant to a broad academic and industrial community interested in nanomaterial design.