A new type of highly ordered, microphase-separated polymer material is synthesized by simple ionic coupling of a commercial styrene/ethylene oxide twoblock copolymer with a charged end group to an oppositely charged polyelectrolyte by common precipitation from aqueous solution. The characterization of the polymer/polymer complex by small-angle X-ray scattering and polarization microscopy reveals that the comb-like addition complexes formed by ionic grafting build up a mesophase with lamellar morphology and a periodicity of d = 7.1 nm which is easily oriented in mechanic fields.