pi-Conjugated polymers bearing nitro substituent(s), e.g., poly(aryleneethynylene) (PAE) type polymers and poly(4,8-dinitroanthraquinone-1,5-diyl) (P(4,8-NO2-1,5-AQ), show semiconducting properties with electrical conductivities of an order of 10(-7) to 10(-6) S.cm(-1) at room temperature without special oxidation and reduction of the polymer. P(4,8-NO2-1,5-AQ) shows a large shift of phase in alternating current (ac) measurements and a unique magnetism at low temperature.