Most of the polymeric thermoelectric materials represent p-type conductivity; however, those of n-type are very few. We report some novel n-type polymeric materials, which are poly(sulphonic acid diphenyl aniline) (PSDA) and its nanocomposites with polythiophene (PTh). They were synthesized in aqueous media using chemical oxidation polymerization process under the external magnetic field where the flux intensities are 0, 1.5, 2.5, and 4.6 kGauss. As the magnetic flux density increases, absolute values of Seebeck coefficient of PSDA and PSDA/PTh nanocomposite films increased however their conductivity did not changed. The negative sign of Seebeck coefficients indicated that PSDA and PSDA/PTh nanocomposites have n-type conductivity. The highest Seebeck coefficient and power factor were obtained as -2535 mu V/K and 0.031 mu W/mK(2), respectively, for PSDA synthesized under 4.6 kGauss magnetic flux. Changes of the Seebeck coefficient were examined in detail with XPS analysis. FTIR, UV-vis spectroscopy, DLS, and XRD analyzes were also performed for the characterization of the polymers. Their surface morphologies were examined by STEM.