Synthesis and electrochemical properties of chitosan-polyphenol composites

Abstract

A unique series of chitosan-polyphenol composites with superior electrochemical properties, chitosan/poly(2-phenyl hydroquinone) (Ch/PPHQ) and chitosan/poly(2,7-dihydroxy naphthalene) (Ch/PDHN) were synthesized with the phenolic derivates, 2-phenyl hydroquinone (PHQ) and 2,7-dihydroxy naphthalene (DHN) in the presence of chitosan (Ch) biopolymer as a tempate. The synthesized Ch/PPHQ and Ch/PDHN composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), thermal gravimetric (TG) analysis and their behavior of swelling in the distilled water. Moreover, poly(2-phenyl hydroquinone) (PPHQ) and poly(2,7-dihydroxy naphthalene) (PDHN) were synthesized using PHQ and DHN by oxidative polymerization technique. The synthesized polymers were also characterized by the gel permeation chromatography-light scattering (GPC-LS), ultraviolet-visible (UV–vis) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, and carbon nuclear magnetic resonance (13C NMR) spectroscopy. The Mn and Mw values of the synthesized polymers were obtained in the range of 3.4 and 34.7 kDa. The Mn and Mw values of PPHQ are approximately 2.5-fold higher than the Mn and Mw values of PDHN. Additionally, The Mn and Mw values of PPHQ and PDHN are 1.5–2.5 times higher than the PPHQ* and PDHN* synthesized in Ch matrix. The prepared Ch/PPHQ and Ch/PDHN composites are redox-active materials. The EHOMO and ELUMO values of PPHQ, Ch/PPHQ, PDHN, and Ch/PDHN materials were calculated in the range of −4.95 to −5.36 eV and − 3.01 – −3.53 eV by measuring the oxidation (Eox) and the reduction (Ered) potential values by the cyclic voltammetry (CV). Moreover, the Eg values of PPHQ, Ch/PPHQ, PDHN, and Ch/PDHN were calculated in the range of 1.54–2.14 from the obtained EHOMO and ELUMO values. It is seen that Ch/PPHQ and Ch/PDHN composites have lower Eg values than PPHQ and PDHN. According to these results, it can be attributed that Ch/PPHQ and Ch/PDHN composites have preferable electrochemical properties by comparison with the PPHQ and PDHN.