The doping of polyaniline has been achieved by introducing the dopant molecule into the solid, undoped polymer without the use of an auxiliary solvent. Complex formation in the solid phase occurs at elevated temperatures and results in the formation of a soluble and processable conducting complex. The complexation was followed by calorimetric studies during a heating scan and the exothermic heat complexation has been observed for the first time. The doping process is similar to the oxidation of an emeraldine base with traditional protonic acid doping, as observed by u.v. and i.r. spectroscopies. The improved processing conditions may be the result of the formation of a layered structure with strongly anisotropic characteristics, as determined by X-ray diffraction measurements.