Formation mechanism, electronic properties & microwave shielding by nano-structured polyanilines prepared by template free route using surfactant dopants

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Abstract
Conducting polymers are at the forefront of nanomaterial's research but the fundamental mechanisms that govern the formation of functional nanostructures and control their electromagnetic (EM) properties are still unknown. Herein, we report for the first time a detailed correlation between acquired morphology, structural, spectral, electrical and EM properties of the polyaniline (PANI) nanostructures synthesized by a template free route using surfactant dopants as structure directing agents. Aniline has been emulsion polymerized in the presence of different sulfonic acids viz. dodecylbenzenesulfonic acid, camphorsulfonic acid, ligninsulfonic acid & cardanolazophenylsulfonic acid and the formed PANIs have been designated as PDB, PCS, PLS and PCD, respectively. The SEM investigations revealed that the morphology is critically dependent on the nature of the dopant, while FTIR, XRD, EPR and UV-visible studies revealed that doping level follows the order PCD < PLS < PCS < PDB, which agrees with electrical conductivity (2.09 S cm−1 for PDB & 0.73 S cm−1 for PCD) and microwave shielding trends (SET = −23.58 dB and −55.04 dB for PCD and PDB, respectively). The observed SET trend can be attributed to the highest microwave conductivity, dielectric losses & loss tangent with lowest skin depth value for PDB. Such high attenuation levels (i.e. blocking of >99.999% of incident EM radiation) demonstrate the potential of these materials for making future microwave shields.

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