In this article, morphological structures are presented that are formed during spin coating of thin composite polymer films, containing a conjugated polymer. The system under study is a mixture of electrically conductive polyaniline doped with dodecylbenzenesulfonic acid and a conventional, nonconducting polymerpolystyrene or poly(methyl methacrylate). The dopant strongly influences film morphology, acting as a surfactant at a polymer/polymer interface. The effect of solution composition, spin-coating atmosphere, and solvent on final morphology is analyzed. Experimental data were collected by means of several techniques: dynamic Secondary Ion Mass Spectrometry, Atomic Force Microscopy, UVVis spectroscopy, and optical microscopy. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013