Polyaniline conductivity, variation with

Polypyrrole or polyaniline loaded fabrics have been studied as microwave absorbers either in the form of pure fabric or composites [84,80-92]. The application involves their use either under the form of multilayer absorbers [86], camouflage nets [93], or absorber with continuous variation of conductivity inside the plane [94] (edge cards for use in low observable technologies). An example of microwave properties which can be achieved with this type of material is given in Figure 8.6. 

Figure 8.17. Variation of relaxation frequency with static conductivity level for polyaniline samples synthesised in HBF4, HCl or NH4F/2.35 HF and poly(3-octylthiophene) based samples (POT and POT/EVA).

The scanning Kelvin probe (SKP,. similar to the EFM technique) permits determination of the work function of CP films. This technique has been used to characterize delamination of a polyaniline containing primer combined with an epoxy topcoat [63] and also to probe the doping-level distribution (from the work function variation) in a conducting poly(2,2 -bithiophene) film [64]. 

In blends containing polyaniline doped with HDBSA, no significant variation in the temperature dependence behavior between PANI-0.5-HDBSA / nylon 6 and PANI-0.5-HDBSA / nylon 12 is observed, although a weaker temperature dependence is expected for tiie latter blend. In this case, a larger fraction of the doping acid is expected to remain in the nylon 12 matrix rather than in nylon 6. This would result in lower carrier concentration for the PANI-0.5-HDBSA in the nylon 12 host and a stronger than expected temperature dependence of conductivity. 

Eeonomers are a new class of conductive additives for thermoplastics made via in-situ deposition of intrinsically conductive polyaniline or polypyrrole on carbon black. Eeonomers are highly thermally stable, pH neutral conductive materials that are compatible with the chemistry and melt processing conditions of acid sensitive polymers. Compounding studies with thermoplastics indicate better electrical, mechanical, and melt flow properties of Eeonomer blends as compared to blends with traditional carbon blacks. In co-continuous plastic blends it was possible to fine tune the polarity of Eeonomer by varying the conductive polymer to CB ratio. The same variation affords very low percolation thresholds due to preferred Eeonomer localization at the 2D phase boundary. 

The discovery of highly conducting poly acetylene in 1977 [1] prompted the synthesis of other polymers with conjugated 7r-systems such as polypyrrole [2], poly-p-phenyl-ene [3], poly-p-phenylenevinylene [4], polyphenylenesulflde [5, 6], polyaniline [7], as well as of other poly heterocycles such as polythiophene [8], polyfuran [8], poly-selenophene [9], or more extended polyaromatics such as polyazulene [10]. Because they can have a variety of structural variations, polythiophenes have become the type of conducting polymer most frequently investigated because conductivity is mostly unaffected by substituents [11]. In addition, both conducting and semiconducting polythiophenes are very stable and readily characterized. 

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