Self-assembled polyaniline nanotubes and nanoribbons/titanium dioxide nanocomposites

Abstract

Self-assembled polyaniline (PANI) nanotubes, accompanied with nanoribbons, were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in an aqueous medium, in the presence of colloidal titanium dioxide (TiO2) nanoparticles of 4.5 nm size, without added acid. The morphology, structure, and physicochemical properties of the PANI/TiO2 nanocomposites, prepared at various initial aniline/TiO2 mole ratios, were studied by scanning (SEM) and transmission (TEM) electron microscopies, FTIR, Raman and inductively coupled plasma optical emission (ICP-OES) spectroscopies, elemental analysis, X-ray powder diffraction (XRPD), conductivity measurements, and thermogravimetric analysis (TGA). The electrical conductivity of PANI/TiO2 nanocomposites increases in the range 3.8 × 10-4 to 1.1 × 10-3 S cm-1 by increasing aniline/TiO2 mole ratio from 1 to 10. The morphology of PANI/TiO2 nanocomposites significantly depends on the initial aniline/TiO2 mole ratio. In the morphology of the nanocomposite synthesized using aniline/TiO2 mole ratio 10, nanotubes accompanied with nanosheets prevail. The nanocomposite synthesized at aniline/TiO2 mole ratio 5 consists of the network of nanotubes (an outer diameter 30-40 nm, an inner diameter 4-7 nm) and nanorods (diameter 50-90 nm), accompanied with nanoribbons (a thickness, width, and length in the range of 50-70 nm, 160-350 nm, and ∼1-3 μm, respectively). The PANI/TiO2 nanocomposite synthesized at aniline/TiO2 mole ratio 2 contains polyhedral submicrometre particles accompanied with nanotubes, while the nanocomposite prepared at aniline/TiO2 mole ratio 1 consists of agglomerated nanofibers, submicrometre and nanoparticles. The presence of emeraldine salt form of PANI, linear and branched PANI chains, and phenazine units in PANI/TiO2 nanocomposites was proved by FTIR and Raman spectroscopies. The improved thermal stability of PANI matrix in all PANI/TiO2 nanocomposites was observed. © 2010 Elsevier B.V. All rights reserved.