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Exploring Lignin Conformation in Organic and Deep Eutectic Solvents Using Small-Angle Neutron Scattering

Sarkar, Subramee LU ; Kroon, Maggie LU ; Papp, Daniel LU ; Martin, Nicolas ; Turner, Charlotta LU orcid and Edler, Karen J. LU orcid (2026) In Langmuir 42(1).
Abstract
Lignin, a structurally intricate and heterogeneous phenolic biopolymer,
holds considerable promise as a sustainable alternative to
petrochemical-derived materials across diverse applications in the
energy and materials sectors. However, precise lignin molecular weight
and structure determination remains challenging due to its intrinsic
tendency to aggregate in solution and the absence of chemically
analogous polymer standards for chromatographic techniques. By employing
small-angle neutron scattering, this study aims at precise measurement
of lignin’s polymeric conformation, aggregation behavior, and radius of
gyration in organic gel permeation chromatography/NMR solvent,
tetrahydrofuran... (More)
Lignin, a structurally intricate and heterogeneous phenolic biopolymer,
holds considerable promise as a sustainable alternative to
petrochemical-derived materials across diverse applications in the
energy and materials sectors. However, precise lignin molecular weight
and structure determination remains challenging due to its intrinsic
tendency to aggregate in solution and the absence of chemically
analogous polymer standards for chromatographic techniques. By employing
small-angle neutron scattering, this study aims at precise measurement
of lignin’s polymeric conformation, aggregation behavior, and radius of
gyration in organic gel permeation chromatography/NMR solvent,
tetrahydrofuran (THF), and in an emerging class of solvent systems known
as deep eutectic solvents (DES). These “designer” solvents, formed from
tailored hydrogen bond donors and acceptors, are gaining importance for
lignin extraction from biomass and analytical characterization.
However, their influence on lignin conformation in solutions remains
unexplored. Our study reveals that both organosolv and Indulin AT kraft
lignin in THF exhibit loosely associated polymeric conformations. Upon D2O
addition, Indulin AT undergoes moderate swelling, suggestive of partial
dissolution, while organosolv lignin undergoes substantial elongation
with directional ordering, resulting in flexible rod-like structures.
Lignin oil from a reductive catalytic fractionation process (RCF), in
contrast, remains well-dispersed in THF and shows minimal structural
change with solvent polarity modulation via D2O addition.
Indulin AT and organosolv lignin solvated in the choline chloride/oxalic
acid/ethylene glycol DES adopt dense, cylindrical morphologies. These
structures show moderate temperature sensitivity and notable resistance
to D2O-induced structural perturbation, highlighting strong
lignin–DES interactions. Additionally, lignin extracted from cocoa bean
shells using a diol-based DES and subsequently dissolved in the same
solvent demonstrates a fractal-like morphology, which evolves with D2O
content and temperature, revealing a complex solvation landscape. These
results offer molecular-level insight into lignin’s solvent-dependent
structural transitions, enabling more accurate molecular weight
estimation and supporting optimization of lignin processing for
high-performance biobased formulations and advanced materials. (Less)
Please use this url to cite or link to this publication:
author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
42
issue
1
publisher
The American Chemical Society (ACS)
ISSN
0743-7463
DOI
10.1021/acs.langmuir.5c03558
project
Deep Eutectic Solvent/CO2 Mixtures for Lignin Processing
CO2 Fluidised Deep Eutectic Systems for Materials Processing
language
English
LU publication?
yes
id
45b797e3-774d-4968-aa74-507677c7daee
date added to LUP
2026-01-10 14:43:37
date last changed
2026-01-16 14:35:11
@article{45b797e3-774d-4968-aa74-507677c7daee,
  abstract     = {{Lignin, a structurally intricate and heterogeneous phenolic biopolymer, <br>
holds considerable promise as a sustainable alternative to <br>
petrochemical-derived materials across diverse applications in the <br>
energy and materials sectors. However, precise lignin molecular weight <br>
and structure determination remains challenging due to its intrinsic <br>
tendency to aggregate in solution and the absence of chemically <br>
analogous polymer standards for chromatographic techniques. By employing<br>
 small-angle neutron scattering, this study aims at precise measurement <br>
of lignin’s polymeric conformation, aggregation behavior, and radius of <br>
gyration in organic gel permeation chromatography/NMR solvent, <br>
tetrahydrofuran (THF), and in an emerging class of solvent systems known<br>
 as deep eutectic solvents (DES). These “designer” solvents, formed from<br>
 tailored hydrogen bond donors and acceptors, are gaining importance for<br>
 lignin extraction from biomass and analytical characterization. <br>
However, their influence on lignin conformation in solutions remains <br>
unexplored. Our study reveals that both organosolv and Indulin AT kraft <br>
lignin in THF exhibit loosely associated polymeric conformations. Upon D<sub>2</sub>O<br>
 addition, Indulin AT undergoes moderate swelling, suggestive of partial<br>
 dissolution, while organosolv lignin undergoes substantial elongation <br>
with directional ordering, resulting in flexible rod-like structures. <br>
Lignin oil from a reductive catalytic fractionation process (RCF), in <br>
contrast, remains well-dispersed in THF and shows minimal structural <br>
change with solvent polarity modulation via D<sub>2</sub>O addition. <br>
Indulin AT and organosolv lignin solvated in the choline chloride/oxalic<br>
 acid/ethylene glycol DES adopt dense, cylindrical morphologies. These <br>
structures show moderate temperature sensitivity and notable resistance <br>
to D<sub>2</sub>O-induced structural perturbation, highlighting strong <br>
lignin–DES interactions. Additionally, lignin extracted from cocoa bean <br>
shells using a diol-based DES and subsequently dissolved in the same <br>
solvent demonstrates a fractal-like morphology, which evolves with D<sub>2</sub>O<br>
 content and temperature, revealing a complex solvation landscape. These<br>
 results offer molecular-level insight into lignin’s solvent-dependent <br>
structural transitions, enabling more accurate molecular weight <br>
estimation and supporting optimization of lignin processing for <br>
high-performance biobased formulations and advanced materials.}},
  author       = {{Sarkar, Subramee and Kroon, Maggie and Papp, Daniel and Martin, Nicolas and Turner, Charlotta and Edler, Karen J.}},
  issn         = {{0743-7463}},
  language     = {{eng}},
  month        = {{01}},
  number       = {{1}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Langmuir}},
  title        = {{Exploring Lignin Conformation in Organic and Deep Eutectic Solvents Using Small-Angle Neutron Scattering}},
  url          = {{http://dx.doi.org/10.1021/acs.langmuir.5c03558}},
  doi          = {{10.1021/acs.langmuir.5c03558}},
  volume       = {{42}},
  year         = {{2026}},
}