Phenolic Hydroxyl Groups in the Lignin Polymer Affect the Formation of Lignin Nanoparticles

Jae Hoon Lee,In-Gyu Choi,Tae Min Kim,Joon Weon Choi

doi:10.3390/nano11071790

Abstract

Alkaline soda lignin (AL) was sequentially fractionated into six fractions of different molecular size by means of solvent extraction and their phenolic hydroxyl groups were chemoselectively methylated to determine their effect on nanoparticle formation of lignin polymers. The effect of the lignin structure on the physical properties of nanoparticles was also clarified in this study. Nanoparticles were obtained from neat alkaline soda lignin (ALNP), solvent-extracted fractions (FALNPs, i.d. 414–1214 nm), and methylated lignins (MALNPs, i.d. 516–721 nm) via the nanoprecipitation method. Specifically, the size properties of MALNPs showed a high negative correlation (R2 = 0.95) with the phenolic hydroxyl group amount. This indicates that the phenolic hydroxyl groups in lignin could be influenced on the nucleation or condensation during the nanoprecipitation process. Lignin nanoparticles exhibited high colloidal stability, and most of them also showed good in vitro cell viability. This study presents a possible way to control nanoparticle size by blocking specific functional groups and decreasing the interaction between hydroxyl groups of lignin.

Highlights

Interest in the utilization of technical lignin as a high-value source has increased since around 70 million tons of lignin byproduct are generated annually worldwide in the pulping/paper industry and 10 million tons per year are generated in biorefineries [1,2]
98% of the extracted lignin solution is just combusted for heat in pulp plants, and less than 2% of the lignin byproduct is converted into commercial products
We evaluated the high potential of kraft lignin as a source of biocompatible nano-sized material and focused on the effect of the lignin structure on the sizes of the nanoparticles [10]

Summary

Introduction

98% of the extracted lignin solution is just combusted for heat in pulp plants, and less than 2% of the lignin byproduct is converted into commercial products

Objectives

Methods

Results

Conclusion