Polyphenols of Wood Bark: Organic Precursors for the Production of Polymer Aerogels

Abstract

A new method for preparation of organic aerogels by sol–gel polymerization of formaldehyde with polyphenols (PPs), isolated from larch bark and birch bark, was developed. The functional composition and properties of the original polyphenols were studied by thermogravimetric methods and FTIR spectroscopy. It was found that larch polyphenol material had higher thermal stability in the temperature range 25−700°C, while the process of thermal decomposition of birch bark polyphenols completes at 600°C. It has been established that polyphenol larch compounds contain more aromatic structures and hydroxyl groups. The effect of the pH of gelation solutions in the range from 4 to 12 on the porous structure of organic gels synthesized from polyphenols was studied. The porous structures and adsorption properties of polyphenol-formaldehyde organic gels were studied using the BET method, scanning electron microscopy and sorption (methylene blue and gelatin). It was shown that an increase in pH contributes to the formation of a product with a more compacted texture. The electron microscopic images of polymer gels demonstrate a uniform granular texture with visible microglobules with an average particle size of ≈50−70 nm.