Carboxymethyl cellulose: an efficient material in enhancing alternating current conductivity of HCl doped polyaniline

In the present research, to enhance the alternating current conductivity of polyaniline (PANI), carboxymethyl cellulose (CMC), a biopolymer, is used to prepare optimized polyaniline-carboxymethyl cellulose (PANI-CMC) composite. The composite was synthesized by in situ polymerization and then characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Improvement in π-electron delocalization in the composite due to CMC was confirmed from FTIR studies. Decrease in d-spacing and inter-chain separation of PANI chains and increase in the degree of crystallinity of the composite, all determined from XRD studies suggested increase in conductivity of the composite. SEM image of the composite has shown crumpled PANI on CMC forming a kind of network facilitating easier transport of charge carriers. Alternating current (AC) response characteristics of PANI-CMC composite were investigated in the frequency range 100 Hz–1 MHz and comparatively analyzed with those of pristine PANI. Increase in AC conductivity of PANI-CMC composite by one order magnitude as compared to that of PANI, mainly due to the presence of CMC in it, was confirmed experimentally. Decrease in density of states at Fermi level of PANI-CMC composite as compared to that of PANI calculated as per correlated barrier hopping model confirmed and supported experimentally observed increase in AC conductivity of the composite. So, CMC as a component of PANI based composites can effectively replace metals/metal oxides in increasing AC conductivity of such composites and has the potential for applications in electronic circuit elements and sensors.