Influence of preparation procedure on the conductivity and transparency of SWCNT-polymer nanocomposites

Nanostructuring of polymers has opened up new perspectives for multi-functional materials. In this paper we report on the feasibility of preparing transparent and conducting polymer nanocomposites based on poly(ethylene terephthalate) (PET) and single wall carbon nanotubes (SWCNT) as additive. Polymer nanocomposites were prepared by two different methods, direct mixing in the melt (DM) and in situ polymerization (I-SP). Samples prepared by DM show a low percolation threshold for electric conductivity, ϕc = 0.024 wt.% of SWCNT, and are more transparent to light than samples prepared by I-SP. Particularly, a DM composite with composition just above ϕc exhibits a conductivity of ∼10−8 S/cm and about 70% of transmittance to visible light. Better electrical and optical properties of nanocomposites prepared by DM in relation to those prepared by I-SP can be explained by assuming that a certain level of aggregation of SWCNT favors the formation of electrical pathways and reduces the number of scatters of light, hence favoring the transmittance of the visible light through these materials.