Siberian Federal University

The paper describes a promising route for the synthesis of novel organic xerogels from naturally occurring, renewable resources using pine-derived polyphenols as suitable initial precursors with relatively low cost. Methods of organic xerogels synthesis based on the use of condensed tannins and ethanol lignin isolated respectively from pine bark and wood are proposed. The effect of cross-linking agent nature – formaldehyde or furfuryl alcohol on the porous structure of resulting organic tannin (lignin)-formaldehyde and tannin (lignin)-furfuryl xerogels was established. Denser tannin-formaldehyde xerogels are subjected to shrinkage (up to 50 %) in processes of drying, and their bulk density ranges in 0.73–0.80 g/cm3. Porous tannin-furfuryl xerogels almost do not shrink at drying and have bulk density 0.30–0.42 g/cm3. The addition of ethanol lignin to the reaction mixture decreases the shrinkage of organic xerogels, whereas the addition of surfactant has a weak effect on the shrinkage. The chemical and porous structure of organic xerogels was investigated by FTIR, BET and SEM methods. FTIR results showed that lignin-containing xerogel possesses more numerous surface functional groups due to an inclusion of ethanol lignin in the gel structure. According to SEM, the three-dimensional network is characteristic for tannin-formaldehyde xerogels which is built from crosslinked polymer chains formed by globular particles with size about 40–50 nm. The tannin-furfuryl xerogels structure is formed by large agglomerates of particles with size up to 100–150 nm