Different types of molecular interactions in carbon nanotube/conducting polymer composites – A close analysis

Composites of polyaniline (PANI) and multi-wall carbon nanotube (MWNT) were prepared through chemical oxidative and γ-radiation induced polymerization of aniline in the presence of functionalized MWNT and the composites were designated as PANI/MWNT-NC(c) and PANI/MWNT-NC(γ), respectively. The composites were characterized for the structure, morphology, optical and thermal properties through Raman, Fourier transform infrared (FT-IR) spectroscopy, field emission transmission electron microscopy (FETEM), UV–visible spectroscopy and thermogravimetric analysis (TGA). FETEM analysis shows the presence of PANI layer (∼15 nm) in PANI/MWNT-NC(γ) and a PANI layer of ∼10 nm in the case of PANI/MWNT-NC(c). Results from Raman and FT-IR spectroscopy indicate the formation of carboxyl groups on the sidewalls of the MWNTs when the composite was prepared by γ-radiation. The existence of carboxyl groups on the walls of MWNT caused induced doping in PANI for PANI/MWNT-NC(γ). UV–visible spectrum of PANI/MWNT-NC(γ) exhibited an additional band around 470 nm corresponding to the induced doping with carboxyl groups. This band was virtually absent in PANI/MWNT-NC(c). Thus, differences in molecular level interactions between PANI and MWNT influence the properties of the composites prepared by chemical and γ-radiation polymerization.