This work emphasizes the important role of the synthetic parameters in the structure of the polymeric material
obtained in the aniline polymerization. The polymers formed by the oxidative polymerization of aniline by
copper(II) ions in acidic aqueous solution, acetonitrile/water medium, and also copper(II) acetate complex
encapsulated into MCM-41 molecular sieve were characterized by resonance Raman spectroscopy using three
exciting laser lines and other techniques such as UV−vis, FTIR, and XANES (Nitrogen K edge). Additionally
the products were investigated by thermogravimetric analysis and powder X-ray diffraction. When Cu(II)
ions in acidic aqueous medium are used, emeraldine salt (ES−PANI) is formed through the usual head-to-tail polymerization mechanism, while in acetonitrile/water medium a polymer is observed having mainly
phenazine-like rings, quinonediimine, and/or phenylenediamine segments in the chains, suggesting that a
distinct mechanism is operating. The average molecular weights of the free polymers synthesized in water
and in acetronile/water were, respectively, ca. 37 300 and 16 900 Da. The encapsulated polymer synthesized
in Cu(II)-MCM-41 is a polymeric mixture of (i) ES−PANI and (ii) the polymer obtained when this metal
cation was used as oxidant in acetonitrile/water medium. All the characterization data were compared to
those ones obtained for standard free polyaniline and also for the encapsulated polymer into mesoporous
MCM-41 formed by using persulfate in acidic aqueous medium as oxidant.