Abstract
For the past decade, much attention was focused on polysaccharide natural resources for various purposes. Throughout the works, several efforts were reported to prepare new function of chitosan by chemical modifications for renewable energy, such as fuel cell application. This paper focuses on synthesis of the chitosan derivative, namely, O-nitrochitosan which was synthesized at various compositions of sodium hydroxide and reacted with nitric acid fume. Its potential as biopolymer electrolytes was studied. The substitution of nitro group was analyzed by using Attenuated Total Reflectance Fourier Transform Infra-Red (ATR-FTIR) analysis, Nuclear Magnetic Resonance (NMR) and Elemental Analysis (CHNS). The structure was characterized by X-ray Diffraction (XRD) and its thermal properties were examined by using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Whereas, the ionic conductivity of the samples was analyzed by electrochemical impedance spectroscopy (EIS). From the IR spectrum results, the nitro group peaks of O-nitrochitosan, positioned at 1646 and 1355 cm-1, were clearly seen for all pH media. At pH 6, O-nitrochitosan exhibited the highest degree of substitution at 0.74 when analyzed by CHNS analysis and NMR further proved that C-6 of glucosamine ring was shifted to the higher field. However, the thermal stability and glass transition temperatures were decreased with acidic condition. The highest ionic conductivity of O-nitrochitosan was obtained at ~10−6 cm-1. Overall, the electrochemical property of new O-nitrochitosan showed a good improvement as compared to chitosan and other chitosan derivatives. Hence, O-nitrochitosan is a promising biopolymer electrolyte and has the potential to be applied in electrochemical devices.
Highlights
Chitosan is a linear polysaccharide which has D-glucosamine units and N-acetyl-D-glucosamine units linked by β (1 ! 4) [1]
The chemical properties of O-nitrochitosan powder were characterized by using ATR-FTIR, 1H Nuclear Magnetic Resonance (NMR) and CHNS analyses
A strong and broad stretching peak band of O-H can be seen overlapping with N-H peak at 3328 cm-1 as reported by Samantha et al [23]
Summary
Chitosan is a linear polysaccharide which has D-glucosamine units and N-acetyl-D-glucosamine units linked by β (1 ! 4) [1]. The O-nitrochitosan powder was prepared by adding an amount of chitosan in isopropanol solution and stirred. This analysis was conducted to observe changes or shifts in wavelength after comparison between chitosan and chitosan derivative that refers to O-nitrochitosan.
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