Critical and Insulating States

The negative magnetoresistance (MR) in metallic (CH), and PPV samples is quite sensitive to the extent of disorder [18, 20]. Even in the case of oriented metallic samples of (CH),  

Although transport property measurements, like thermoelectric power, specific heat, etc., are important in the critical and insulating regimes, they are not as sensitive as the low temperature conductivity and MR. The linear temperature dependence of thermoelectric power and a linear term in the specific heat (which are typical for metallic systems) have been observed in the insulating regime too. As the system moves into the insulating side the hopping contribution to thermoelectric power (5 dominates over the metallic 

The Curie term in x(T) is rather dominant at low temperatures for systems in the critical and insulating regimes, and the temperature independent Pauli term is usually observed at temperatures greater than 100 K. However, xiT) Is not as sensitive as o(T) and MR for identifying the metallic, critical and insulating regimes near the M-I transition [17]. 

This brief overview of the electrical transport properties in doped conducting polymers highlights the following points  

Handbook of Organic Conductive Molecules and Polymers, Volumes 1-4, Ed., H.S. Nalwa, Wiley, New York, NY, USA, 1997. 

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