Synthesis of daisy-shaped core-shell nanocomposites of chiral poly[(±)-2-(sec-butyl)aniline] in the solid state

A green and simple procedure is reported on the synthesis of a daisy-like core-shell nanocomposite of chiral poly[(+/-)-2-(sec-butyl)aniline]/nanosilica. This morphology is related to the use of nanosilica and a mechanism based on intermolecular interactions between particles of nanosilica and the polymer. The morphology of the samples and their coating were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), SEM-map and energy-dispersive X-ray spectroscopy (EDX). The outstanding feature of this study is that it presents the first report of an in situ formation of daisy-like morphology for polyaniline nanocomposites through one-pot route without using pre-functionalized nanosilica and any other template under the solid-state condition; while this polymer has displayed no specific morphology under most conditions. According to XPS and CHNS analysis, the nigraniline oxidation state was confirmed as well as fully doping of composites (around 75%) in contrast with partial doping of poly[(+/-)-2-(sec-butyl)aniline].HCl salt. The structure of nanosilica was studied by Si-29 NMR. The sample showed a conductivity around 5.2x10(-2) S/cm, consistent with the XPS results which revealed the doping level. In addition, the TLM measurement was applied to determine the contact resistance. In this study, a chiral conductive nanocomposite was prepared under a solid-state condition in compliance with the green chemistry principles. Moreover, it was found that the nanocomposite is in delocalized polaron structure using solid acid as a dopant. Additionally, from the industrial point of view, the processability has been improved due to the introduction of the 2-sec-butyl group within the polymer backbone.