Composites with Non-enriched SWNTs

SWNT/polymer composites could also be made by a two-step fabrication process. For example, SWNT films were first fabricated on glass slides via Mayer rod coating, and then polymers such as PVA, Nafion and polyvinylidenefluoride (PVDF) were infiltrated into SWNT networks. As the polymer occupied the empty space between the nanotubes, a freestanding 

Transparent SWNT/insulating polymer nanocomposites have not been made with high conductivity values, mainly because of the intrinsic charge localization arising from insulating polymer dispersant. In a direct comparison, SWNTs were stabilized with insulating surfactant (SDS) or conductive poly(3,4-ethylenedioxythiophene) (PEDOT) PSS. Both SWNT dispersions were introduced into a polystyrene matrix via a latex-based route. Composites with PEDOT PSS-stabilized SWNTs showed a percolation threshold of 0.18 wt% and a conductivity value of 500 S m compared with 3.8 wt% and 20 S m for the SDS-based composites, respectively. The authors attributed the conductivity enhancement to conduction bridge formed by the conductive polymer between adjacent SWNTs. 

PEDOT with and without the dopant PSS has been the most commonly used conductive polymer for SWNT composites. De et al prepared composite films by vacuum filtration from aqueous dispersions with PEDOT PSS as the matrix and both arc and HiPCO SWNTs as the filler. The optimal performance was observed for a 80 nm thick film containing 60 wt /o arc SWNTs, with a sheet resistance of 80 Q sq at 75 /o transmittance. Electromechanical testing showed these films to be stable under flexing and cycling. Later, a modified PEDOT copolymer with enhanced solubility, perchlorate-doped poly(3,4-ethylenedioxythiophene)-Z /ock-poly(ethyleneox-ide) (P-PEDOT-b-PEO) was used to disperse SWNTs and then to fabricate conductive nanocomposites via vacuum filtration method.The sheet resistance of the composite film was approximately 600 Q sq with 80 /o transmittance. 

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