Electrical transport and morphological studies of polyaniline nanostructures

Polyaniline nanostructures have been synthesized by self-assembly method by varying the dopant to monomer molar ratio. High resolution transmission electron micrographs show how the dopant to monomer molar ratio influences on the morphology and structure. The temperature dependence of dc conductivity study shows semiconducting behavior. From dc conductivity study it has been observed that conductivity increases with increasing dopant concentration and maximum conductivity is attained at dopant to monomer molar ratio of 3:4. From the slope of the reduced activation energy versus temperature plot it is confirmed that the charge transport in polyaniline nanostructures is in insulating regime and dominated by variable range hopping mechanism. In particular, a crossover from 1D to 3D variable range hopping conduction is observed by changing the dopant to monomer molar ratio. With increasing the dopant concentration the 680 nm absorption peak shifted towards higher wavelength range. The red shifting of this peak indicates the increased extent of π-conjugation length. The enhancement of characteristic band intensity at 1336 [cm.sup.-1] in Micro-Raman spectra indicates the increase of delocalization degree. Temperature profiles of the degradation processes have been mapped using thermogravimetry analyzer and it is observed three-step weight losses for all the samples.
INTRODUCTION Conducting polymers are a class of functional materials having alternating single and double carbon-carbon bonds along the polymeric chains. The highly conjugated polymers possess reversible chemical, electrochemical, and physical [...]