Adsorption and Polymerization of Aniline on Cu(II)-Montmorillonite:  Vibrational Spectroscopy and ab Initio Calculation

Abstract

Batch adsorption experiments in the presence of oxygen were performed to study the interlayer reactions of aniline on Cu(II)-montmorillonite in aqueous solutions. At concentrations below a critical value of C C = 2.6 mmol dm-3 only a colored Cu(II)−aniline complex is formed, characterized by a stability constant of log(K assoc/dm3 mol-1) = 1.5. At concentrations beyond C c aniline polymerizes yielding a dark brown product, which is identified by two vibrational spectroscopy techniques, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and FT-Raman spectroscopy. Vibrational assignment of aniline, polyaniline, and the interlayer reaction products of aniline at Cu(II)-montmorillonite was achieved by a comparison of the band position and intensity observed in the ATR and FT-Raman spectra with wavenumbers and intensities (IR and Raman) from ab initio quantum-mechanical calculations. Density functional theory (DFT, B3LYP/6-31G*) has been used to calculate the geometry, frequencies, and intensities (IR and Raman) of aniline. The geometry and vibrational calculations of a four-ring unit (emeraldine base, EB) are believed to be a good representation of the polyaniline at Cu(II)-montmorillonite. The geometry of EB was fully optimized at the Hartree−Fock level of theory. The data of polyaniline presented suggest that IR and Raman data calculated ab initio on relatively short oligomers (quantum-mechanical oligomer approach) may provide valuable information regarding the interpretation of vibrational spectra of polymers. From the comparison of experiments and calculations, it is concluded that a catalytic/intercalation polymerization of aniline to polyaniline took place inside the interlayer of the Cu(II)-montmorillonite clay mineral.

Studying the Polymerization of Aniline on Fullerene

“…For comparison purpose aniline is prepared by adsorption upon Cu(II)-montmorillonite [20,21]. Batch adsorption experiments in the presence of oxygen were performed to study the interlayer reactions of aniline on Cu(II)-montmorillonite in aqueous solutions.…”

“…A scaled quantum mechanical oligomer force field for oligomers of leucoemeraldine base and for one oligomer of the imine form of polyaniline was established [19]. Both vibra-tional spectroscopy and ab initio calculations were used to study the adsorption and polymerization of aniline on Cu(II) montmorillonite [20]. Further vibrational assignment for polyaniline emeraldine base was achieved with FTIR; semiempirical; HF and DFT calculations [21].…”

Sorption of Selected Aromatic Substances—Application of Kinetic Concepts and Quantum Mechanical Modeling

“…For example, such processes were suggested for AN at least above a critical concentration adsorbing on montmorillonite saturated with Cu 2+ or Na + (Ilic et al 2000;Nascimento et al 2004). Thus, a polymerization process will also most likely occur with regard to Ca-montmorillonite at higher concentrations.…”

Ultrasensitive electrochemical immunosensor for squamous cell carcinoma antigen detection using lamellar montmorillonite-gold nanostructures as signal amplification

“…Usually, aniline would exist in the form of cations in acidic solution, so it can insert into Na-Mont and react with the added HAuCl 4 solution. Due to the large surface and cation exchange ability of Na-Mont [24,25], AuNPs and PANI could form largely in the interlayer structures based on the reaction of HAuCl 4 and aniline. The secondary anti-SCC antibodies (Ab 2 ) can be adsorbed onto the Na-Mont surface based on its excellent adsorption ability and the Ab 1 could be immobilized by N-GS due to its excellent electronic conductivity, large surface areas and amounts of edge sites [26][27][28].…”