Aldehyde functionalized multiwalled carbon nanotubes to synthesize highly conducting polyaniline-MWNT thin films

Abstract

Polyaniline (PANI) and its composites with other materials gains great attraction in the field of conducting polymers as their properties can be easily tuned to the desired level. Multiwalled Carbon nanotubes (MWNT) are such a promising material to make composites with PANI. Presence of MWNT in PANI composite enhances its conductivity and makes the composite thermally stable. But dispersivity of PANI-MWNT composite in solvents is very low while preparing thin film samples. To improve the solubility and processability of PANI-MWNT composite, MWNT has to be modified by attaching suitable functional groups to the side walls of carbon nanotubes without changing the composition of nanotubes. The functionalization of multi-walled carbon nanotubes was carried out using HCl treated MWNTs. MWNTs were reacted with formaldehyde and attached into methylol groups (–CH2OH). The presence of methylol group makes the carbon nanotubes more lyophilic than the pristine form and improves the processability of MWNTs and MWNT containing composites. Structural characterization is carried out by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. Electrical characterization of the samples were carried using standard four point probe method. Pristine MWNT shows flat temperature response of DC electrical conductivity. The room temperature conductivity of pristine MWNT, PANI and PANI-MWNT composites are 9.5 S/cm, 2.27 S/cm and 11.8 S/cm respectively. In the present work, we have achieved significant dispersivity of PANI-MWNT composites as a result of the functionalization and the thin film sample shows electrical conductivity of 565.44 S/cm which is very high for conducting polymer composites. These composites show metallic character and its temperature coefficient of resistance (α) is found to be 0.0038 °C−1, which is less than that of copper.