Synthesis and spectroscopic analysis of polydiphenylamine via oxidation with bentonite clay in the solid state

• Developing an innovative synthesis route for diphenylamine oxidative polymerization.
• Comparing the Raman spectra of the prepared chemically with that electrochemically.
• Deconvolution of the band characterizing CC stretching in the Raman spectra.
• Characteristic frequencies of the aromatic, radical cation and dication segments.

In this study, solids of polydiphenylamine (PDPA) synthesized mechanochemically by reaction with bentonite (PDPAOB) were studied using Raman spectroscopy. It was possible to identify the chemical species in the PDPA–bentonite compound. The spectra obtained were compared to the spectra of PDPA prepared chemically by oxidation of DPA with K2S2O8 in the solid state, and PDPA produced electrochemically, with the aim of studying the characteristic frequencies of the aromatic segments (DPB), radical cation (DPB+) and dication (DPB2+) of N,N-diphenylbenzidine (DPB) in the polymer structure of the PDPA. To analyze the segments present, the band characteristic of CC asymmetric stretching of the aromatic ring in the Raman spectra was deconvoluted because of the widening of the band and shifts observed by irradiation at wavelengths of 532 and 785 nm. This procedure showed that there are three distinct contributions in the spectra which facilitate the monitoring of changes in the contributions of the segments in the materials doped with HCl (PDPAOBD) and de-doped with NH4OH, (PDPAOBR).

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