Dielectric behavior and charge transport in polyaniline nanofiber reinforced PMMA composites

PAni nanofibers synthesized by interfacial polymerization were reinforced in the PMMA matrix in different weight ratios. Randomly oriented polyaniline nanofibers were observed in the TEM image with diameter ranging from 20 to 30 nm. The SEM revealed the microstructure of the fiber reinforced composites showing better connectivity. The XRD spectra of the composites showed peaks at 2θ=17.05°, 20.3°, 27.15° and 30.05° that were indexed in a pseudo-orthorhombic unit cell. The dielectric constant measured over a frequency range of 42 Hz–1 MHz and in the temperature range of 303–373 K showed dependence upon frequency, temperature and concentration of the conducting nanofibers in the composites. The ac conductivity (σac) was interpreted as a power law of frequency. The frequency exponent s was found to lie in the range from 0.4 to 0.65 and decreased with the increase in temperature, which suggested that correlated barrier hopping (CBH) was the dominant charge transport mechanism. Existence of polarons as major charge carriers was confirmed by the low values of polaron binding energy (WM). Decrease in the values of density of states N(EF) with the increase in PAni nanofiber concentration indicated increased delocalization of electronic states in the band gap causing the increase in ac conductivity.