Structure and electrophysical properties of carbogels based on the interpolyelectrolyte complex lignosulfonate - chitosan with various composition

Abstract The new approach to the synthesis of highly porous polyfunctional nanomaterials with “fullerene-like” morphology was shown. Obtained materials have developed micro- (mainly supermicropores) and mesoporous structure, narrow particle size distribution (particle size of 35–60 nm), low content of minor elements (metal and sulfur), having electrically conductive properties. The supramolecular systems (interpolyelectrolyte complex) formed by the self-assembly and molecular recognition of two biopolymers with various structural organizations were used as a precursor. The interpolyelectrolyte complex was prepared by mixing of the dendritic-like polyelectrolyte lignosulfonate and the linear polysaccharide chitosan with different molar ratios. The idea of this research consists in the sequential combination of interpolymer complexation, supercritical fluid treatment and high-temperature carbonization. New carbon materials contain up to 91.5% of carbon and nitrogen content is up to 6.9%. Organic sulfur is removed from the samples as volatile compounds during carbonation. Metal ions (K + , Na + , Li + ) and nitrogen compounds embedded in the structure of aerogels at the stage of complex formation change the structure. It leads to improve the porous structure and allows to obtain the carbogels with the high total pore volume (up to 0.51 cm 3  g −1 ), average pore width (up to 4.6 nm) and specific surface area up to 465 m 2  g −1 . The maximum specific surface area of the carbogels is formed in the slow pyrolysis mode at the temperature of 600 °C for carbogels based on interpolyelectrolyte complex lignosulfonate-chitosan with Z = 1.4. The size of the cation in the composition of lignosulfonate does not affect the size distribution of micropores (supermicropores) of the carbogel, however, the presence of an alkali metal cation in the structure leads to an increase in the volume of micropores, the total pore volume and the average pore width. It was shown that new carbon nanomaterials have a specific electrical conductivity of the order of 10 −4  S m −1 and possess electrically conductive properties. Electrophysical properties of carbogels directly depend on their molar composition. The specific electrical conductivity of carbogels based on interpolyelectrolyte complex with an excess of chitosan (Z = 1.4) in the composition is in five times higher than for the carbogels based on stoichiometric interpolyelectrolyte complex (Z = 1). Carbon nanomaterials are promising for practical use as electrically conductive dispersed particles in small-sized nanoelectronics devices.