Low-temperature heat capacities of polyaniline and polyaniline polymethylmethacrylate blends

Heat-capacity measurements between 0.4 and 10 K have been made on doped polyaniline and its blends with polymethylmethacrylate. At lower temperatures, a finite electronic term (γ) prevails in all samples. The value of γ for polyaniline is 14 mJ/mol ${\mathrm{K}}^2$, but higher by a factor of about 6 for the blends. Using the free-electron model, the corresponding density of states at the Fermi level $\left[{N(E}_F\right)]$ are calculated and compared with that obtained from magnetic susceptibility measurements on the same samples. It is shown that caution must be used in determining ${N(E}_F)$ from magnetic susceptibility measurements in polyaniline and other less conducting polymeric materials.