Conducting polymers formation effect

Zhang et al. studied the effect of conductive network formation in a polymer melt on the conductivity of MWNT/TPU composite systems (91). An extremely low percolation threshold of 0.13 wt% was achieved in hot-pressed composite film samples, whereas a much higher CNT concentration (3-4 wt%) is needed to form a conductive network in extruded composite strands. This was explained in terms of the dynamic percolation behavior of the CNT network in the polymer melt. The conductivity of extruded strand showed a hopping resistivity dominated behavior at low concentrations and a dynamic percolation induced network dominated behavior at higher concentrations. It was shown that a higher temperature can reduce the filler concentration required for the dynamic percolation to take effect. 

The enhancement of specific capacitance for carbon materials is generally realized by the usage of pseudocapacitance effects, which depend on the surface functionality of carbon and on the presence of electro-active species (termed supercapacitors) [162-164]. Several modifications (i.e., oxidation of carbon for increasing the surface functionality, formation of carbon/conducting polymers composites or insertion of electroactive particles of transition metals) can be carried out to increase the pseudocapacitance that arises fi om faradaic reactions. However, the enhancement of the capacitance connected with faradaic reactions of surface groups often contributes to an increase in the self-discharge of the capacitor due to the instability of the functionalities [165]. 

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