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Polymers 2018, 10(8), 869; https://doi.org/10.3390/polym10080869

Characterization of Lignin Extracted from Willow by Deep Eutectic Solvent Treatments

1
State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences, Shandong 250353, China
2
Department of Forest Biomaterials, North Carolina State University, Box 8005, Raleigh, NC 27695-8005, USA
*
Authors to whom correspondence should be addressed.
Received: 15 July 2018 / Revised: 31 July 2018 / Accepted: 3 August 2018 / Published: 5 August 2018
(This article belongs to the Special Issue Lignin Polymers: Structures, Reactions and Applications)
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Abstract

Purity, morphology, and structural characterization of synthesized deep eutectic solvent (DES)-lignins (D6h, D9h, D12h, D18h, D24h) extracted from willow (Salix matsudana cv. Zhuliu) after treatment with a 1:10 molar ratio of choline chloride and lactic acid at 120 °C for 6, 9, 12, 18, and 24 h were carried out. The purity of DES-lignin was ~95.4%. The proportion of hydrogen (H) in DES-lignin samples increased from 4.22% to 6.90% with lignin extraction time. The DES-lignin samples had low number/weight average molecular weights (1348.1/1806.7 to 920.2/1042.5 g/mol, from D6h to D24h) and low particle sizes (702–400 nm). Atomic force microscopy (AFM) analysis demonstrated that DES-lignin nanoparticles had smooth surfaces and diameters of 200–420 nm. Syringyl (S) units were dominant, and total phenolic hydroxyl content and total hydroxyl content reached their highest values of 2.05 and 3.42 mmol·g−1 in D12h and D6h, respectively. β-Aryl ether (β-O-4) linkages were eliminated during DES treatment. View Full-Text
Keywords: deep eutectic solvent (DES); lignin; DES-lignin; molecular weights; lignin nanoparticles; β-aryl ether bonds deep eutectic solvent (DES); lignin; DES-lignin; molecular weights; lignin nanoparticles; β-aryl ether bonds
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Lyu, G.; Li, T.; Ji, X.; Yang, G.; Liu, Y.; Lucia, L.A.; Chen, J. Characterization of Lignin Extracted from Willow by Deep Eutectic Solvent Treatments. Polymers 2018, 10, 869.

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