Structural regulation of lignin/silica nanocomposites by altering the content of quaternary ammonium groups grafted into softwood kraft lignin

Abstract

In this work, cationic lignin derivatives were synthesized by grafting reaction of lignin and 3-chloro-2-hydroxypropyltrimethylammonium chloride. Then the synthesized cationic lignins were used to prepare lignin/silica nanocomposites (LSNCs) via a green co-precipitation method. The following characterizations, particle size distribution, SEM, TEM, XRD, FT-IR, XPS, static contact angle, specific surface area, and pore size distribution, were employed to understand the dispersity, morphology, crystal structure, and textural property of different LSNCs. The results showed that lignin with low content of cationic quaternary ammonium (QA) groups couldn’t support the formation of uniform LSNCs, while lignin with moderate content of QA groups leaded to the formation of uniform LSNCs with a core-shell structure, lignin/silica hybrids in inner side and thin layer of lignin on surface. When the content of QA groups in lignin was high, the prepared LSNCs presented porous strawberry-like structure, lignin/silica hybrids at inside and coating layer of silica nanoparticles within 10 nm on surface.