# Alcohol-Decorated Lignins for Nanoparticle Formation through Reactive Fractionation in Ternary Deep Eutectic Solvent Systems

## TL;DR

Researchers developed a method to isolate lignin from wood using a special solvent system, enabling the creation of stable lignin nanoparticles with potential material applications.

## Contribution

The study introduces a novel reactive fractionation method using ternary deep eutectic solvents to isolate lignin with controlled structural features for nanoparticle formation.

## Key findings

- High lignin yield (66%) with 75% retention of β-O-4 aryl ether linkages was achieved under optimized conditions.
- EG incorporation in lignin is temperature- and time-dependent, preserving structure at 140–160 °C.
- Lignin nanoparticles with tunable size and stability were successfully synthesized using pH-induced flash precipitation.

## Abstract

This study explores the use of ternary deep eutectic
solvent (DES)
systems composed of choline chloride (ChCl), oxalic acid (OA), and
ethylene glycol (EG) for the efficient fractionation of lignocellulosic
biomass and isolation of lignins with diverse structural features
and EG incorporation levels. Reactive fractionation of birchwood under
optimized conditions resulted in a high lignin yield (66%), with up
to 75% retention of β-O-4 aryl ether linkages. Systematic variation
of temperature (80–200 °C), reaction time, and DES composition
showed that EG incorporation is both temperature- and time-dependent,
with optimal structural preservation observed at 140–160 °C
and short reaction times. Furthermore, 2D HSQC NMR and GPC analyses
revealed that increasing temperatures promote the cleavage of aryl
ether linkages, while a higher EG content in the DES mitigates structural
degradation. The resulting EG-decorated lignins were successfully
applied to the controlled synthesis of lignin nanoparticles (LNPs)
via hydrotropic and pH-induced flash precipitation methods. The latter
allowed one to obtain LNPs with size tunability, colloidal stability,
and favorable surface charge, highlighting their potential for material
applications. Overall, this study provides critical insights into
the structure-processing relationships of DES-isolated lignins and
establishes a promising approach to their valorization into functional
nanomaterials.