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a) b - École Polytechnique de Montréal

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chemical and weathering resistance, piezo-electric properties and good flexibility(Bliznyuk et al.,<br />

2005; Privalko, et al., 2005). Fraysse et al(Fraysse, et al., 2000) were able to <strong>de</strong>crease the<br />

percolation threshold of PANI sharply in a PANI/PMMA solution blend to 0.5 wt% of PANI.<br />

Although the above methods using in-situ polymerization and polymer solution blending can<br />

result in very low percolation thresholds of conductive polymer, they suffer from serious<br />

disadvantageous such as poor mechanical properties. In addition, clearly the environmental and<br />

health related issues associated with solvents and solvent removal are critical concerns. A melt<br />

blending approach, from this point of view, is potentially a much more robust and<br />

environmentally friendly approach.<br />

In the case of melt-processing, Shacklette et al.(Shacklette, et al., 1993) reported percolation<br />

thresholds in a range of 6-10% for PANI dispersed in polar polymers such as polycaprolactone<br />

and poly(ethylene terphthalate glycol). Zilberman et al.(Zilberman, et al., 2000d) have reported<br />

percolation thresholds of PS/PANI and linear low-<strong>de</strong>nsity polyethylene(LLDPE)/PANI of about<br />

30 wt% of PANI. They reported a lower percolation value of 20 wt% PANI for the binary blend<br />

composed of CoPA/PANI.<br />

Levon et al.(Levon, et al., 1993) were the first to suggest the concept of double percolation in a<br />

ternary polymer blend consisting of a conductive polymer. This double percolated system was<br />

comprised of a connected path within a connected path, the latter of which is conducting.<br />

Zilberman et al.(Zilberman, et al., 2000d) observed a high-quality conductive PANI network in a<br />

CoPA/LLDPE/PANI ternary blend and a poor-quality PANI network in a<br />

(PS+DOP)/LLDPE/PANI blend. Narkis and coworkers(Haba, et al., 2000; Narkis, et al., 2000a;<br />

Segal, et al., 2001)exten<strong>de</strong>d and <strong>de</strong>veloped these previous works by blending PANI with other<br />

homopolymers via different methods mostly by using the methodology of a double percolated<br />

morphology to <strong>de</strong>crease the percolation threshold and increase mechanical properties. They<br />

showed that for several melt processed PANI/polymer blends, the conductivity results reveal a<br />

percolation threshold of approximately 20%. That work also shows that, in ternary blends<br />

consisting of PANI and two immiscible polymers, the PANI is preferentially located in one of<br />

the constituting polymers. They found that PANI always prefers to locate in one phase rather<br />

than situating at the interface(Zilberman, et al., 2000d). In all previous works performed on<br />

PANI, the percolation threshold concentration of PANI was <strong>de</strong>termined based on the onset of<br />

increase in the conductivity as a function of composition. In most of those cases, the sample<br />

101

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