Self-assembly of a renewable lignin biopolymer in nanoparticles with multiple morphologies

Lignin is considered one of the main biorenewable polymers from natural resources. Each year, a large amount of lignin is generated as a waste byproduct of the pulping process in the paper industry. However, it is seldom treated as a value-added material because of its undefined structure, the diverse methods of isolation and processing, and the origin of the material; these greatly hinder its application. Therefore, it is of great significance to explore new potential applications of this readily available yet underappreciated natural product. In this study, we developed a preparation method of lignin-based microstructures or nanostructures via self-assembly. We created various self-assembled nanostructures, including nanocubes, nanorods, nano-octahedrons, nanobranches, and other morphologies, by choosing different types of simple inorganic acids at various pHs. Some of these nanostructures have never been reported. These structures were fully characterized with scanning electron microscopy, ultraviolet–visible spectroscopy, and dynamic light scattering. All of them were uniform and stable. They displayed little or no cytotoxicity to cells in vitro at concentrations up to 1024 μg/mL. We hope the results of this study provide some insight for the future development of new applications of lignin-based materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47482.