REACTION OF ANILINE WITH FEOCL - FORMATION AND ORDERING OF CONDUCTINGPOLYANILINE IN A CRYSTALLINE LAYERED HOST

A detailed study of the intercalative polymerization reaction of anili ne with FeOCl, an extensive physicochemical and spectroscopic characte rization of the products, and their oxidative behavior in air is prese nted. FeOCl reacts with excess aniline in CH3CN at 25 degrees C, in ai r, to form black microcrystalline products containing polyaniline (PAN I) of the general formula (PANI)(x)FeOCl (I). X-ray diffraction from a single crystal of (PANI)(x)FeOCl shows that the polymer is intercalat ed in an ordered fashion that is commensurate with the FeOCl lattice. This ordering causes a doubling of the unit cell in the two in-plane d irections (a- and c-) forming a 2a x 2c superlattice. The PANI can be extracted from (I) by FeOCl framework dissolution in acid. Molecular w eight studies of extracted PANI via gel permeation chromatography (GPC ) analysis suggest (M) over bar(w) similar to 6100 and (M) over bar(n) similar to 3500 versus (M) over bar(w) similar to 69 000 and (M) over bar(n) similar to 7700 observed for bulk PANI. Chain lengths of PANI in the intralamellar space are shorter than those of bulk PANI but sho w narrower length distribution. Variable temperature H-2-wide-line NMR of (PANI)(x)FeOCl shows that the polymer chains are significantly con fined with respect to phenyl ring rotation, but the spectra are influe nced by the electron paramagnetism of the host. The (PANI)(x)FeOCl was also characterized by infrared spectroscopy, Mossbauer spectroscopy, electron paramagnetic resonance spectroscopy, thermal gravimetric anal ysis, magnetic susceptibility measurements, and charge-transport measu rements. Mossbauer spectroscopy suggests a mixed-valent FeOCl with a F e2+/Fe3+ ratio in the material similar to 1:9. Aerial oxidation of (PA NI)(x)FeOCl yields an intimate mixture of PANI and beta-FeOOH. The PAN I after oxidation shows a molecular weight intermediate between that e xtracted from fresh (PANI)(x)FeOCl and bulk PANI. The electrical condu ctivity of single crystals is 1.5 x 10(-2) S/cm and features a thermal ly activated temperature dependence consistent with a semiconductor. T hermoelectric power measurements show a positive Seebeck coefficient ( similar to 10 mu V/K) at room temperature which increases steadily wit h decreasing temperature, reaching the value of 100-400 mu V/K at 150 K, consistent with a p-type semiconductor. The charge transport data s uggest that in (PANI)(x)FeOCl the reduced FeOCl framework dominates th e electronic conduction.