Extraction, Purification and Electrical Characterization of Gross Galactomannan and Purified Galactomannan Obtained from Adenanthera pavonina L. Seeds

Abstract

Aiming of self-sustainable production, the search for biodegradable and biocompatible materials has brought with it the need to know the physicochemical and dielectric characteristics of polysaccharide-based composite structures, which can be used as important and promising raw materials for biotechnology and electronic industries. Galactomannans are polysaccharides, extracted from seeds and microbiological sources, consisting of mannose and galactose. In this context, this work aimed to extract, purify and characterize by XRD, FTIR and impedance spectroscopy galactomannan obtained from seeds of Adenanthera pavonina L. The purification process was made with ethyl alcohol at concentrations of 70, 80 and 90 %. Polymeric films were prepared by solvent slow evaporation at low temperatures. XRD measurements revealed that Galactomannan from Adenanthera pavonina L., after purification, has a semi-crystalline structure due to the identification of two peaks the first between 5.849°and 6.118°and the second between 20.011°and 20.247°. FTIR spectra showed the functional groups associated with monosaccharides of the galactomannan from Adenanthera pavonina L. seeds, as well as the typical polysaccharide bands and peaks, confirmed by literature data. The impedance results give an increment on the state-of-the-art of this biomaterial by showing the existence of dielectric relaxations, independent of the degree of purification, using the dielectric modulus formalism. The permittivity analysis reveals the presence of water in the structure of the film, whose dipoles contribute to the relatively high value of the dielectric constant. From the results obtained, it can be concluded that purified galactomannan has the potential for possible applications in the electronics industry as a green and eco-friendly dielectric material.

Dielectric Characterization of Solutions of Galactomannan Extracted from Adenanthera pavonina L.: Effects of Purification and Ethanol Concentration

“…It is noted that the conductivity tends to increase as the solution concentration increases, which may be related to the increase in the number of charge-bearing particles present in galactomannan. This can be because the alcohol causes the dehydration of galactomannan molecules, and therefore as the ethanol concentration increases, the polymer chain's rigidity rises due to increased stiffness in hydrogen bonds, leading to a limitation in polymer chain mobility [40]. Figure 8 shows the AC conductivity as a function of the frequency of GB, GP60, GP70, GP80, GP90, and GP100 samples measured at room temperature.…”

“… Schematic representation of the correlation between the chemical structure and the real part of the permittivity in purified galactomannan solutions [ 40 , 43 , 44 ]. …”