The Effect of Functional Nature on the Dielectric Properties of Slightly Altered Lignins

Objective: The study explores the electrophysical properties of lignins, specifically focusing on their potential applications due to their polyfunctional aromatic nature, conjugation system, and high reactivity in redox interactions. The research aims to investigate the relationship between the functional nature, reaction properties, and dielectric properties of lignins. Methods: The study involved slightly altered dioxane lignin from spruce and modified lignin samples with varying contents of carbonyl and methoxyl groups. The redox and dielectric properties were analyzed, including the effects of functional group content on oxidation potential, electrical conductivity, and complex permittivity. Dielectric spectroscopy was used to measure the conductivity and permittivity in a frequency range of 10–2 to 107 Hz, and the frequency dependences of the complex permittivity were analyzed to identify relaxators in the lignin structure. Results and Discussion: It was found that changes in the content of carbonyl groups significantly influenced the redox properties of lignin, with the effective oxidation potential of phenolic units varying by up to 24 mV. The study also showed that the carbonyl and methoxyl groups affected the real part of the complex permittivity at low frequencies (less than 1 Hz), suggesting that these changes influenced the dielectric properties of lignin. The results indicate that lignin could be a promising material for broadband electrical capacitors. Conclusions: The study concluded that the functional nature of lignin, including the content of carbonyl and methoxyl groups, significantly affects its dielectric and redox properties. These findings suggest that lignin is a promising material for the manufacture of broadband electrical capacitors.