Deciphering lignin heterogeneity in ball milled softwood: unravelling the synergy between the supramolecular cell wall structure and molecular events

Sapouna, Ioanna; Lawoko, Martin

doi:10.1039/d0gc04319b

Cited by 38 publications

(61 citation statements)

References 38 publications

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“…Hence, no standards can represent the entire lignin structure, and this is complicated by different lignin species that are essentially co-polymers of different phenylpropane units. Also, due to its inherent branched structure, , lignin may interact with column packing materials resulting in a delay of elution and an underestimation of molecular weight . Therefore, an absolute molar mass characterization technique is necessary because it provides information that is independent of separation methods and calibration standards.…”

Section: Introductionmentioning

confidence: 99%

Revisiting the Molar Mass and Conformation of Derivatized Fractionated Softwood Kraft Lignin

Liu

Cho

et al. 2021

Biomacromolecules

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The limited utilization of reliable tools and standards for determination of the softwood kraft lignin molar mass and the corresponding molecular conformation hampers elucidation of the structure-property relationships of lignin. At issue, conventional size exclusion chromatography (SEC) is unable to robustly measure the molar mass because of a lack of calibration standards with a similar structure to lignin. In the present work, the determination of the absolute molar mass of acetylated technical lignin was revisited utilizing SEC combined with multi-angle light scattering with a band pass filter to suppress the fluorescence. Fractionated lignin isolated using sequential techniques of solvent and membrane methods was used to enhance the clarity of lightscattering profiles by narrowing the molar mass distribution of lignin fractions. Further information on the molecular conformation of derivatized samples was studied utilizing a differential viscometer, and chemical structures were identified by NMR spectroscopy analysis. Through the help of fractionation, intrinsic viscosity values were determined for the different fractions as a function of molecular weight cut-off membranes. The derivatized acetone-soluble lignin was found to possess a lower molecular weight and an extremely compact structure relative to the derivatized acetone-insoluble fraction based on a significantly lower "α" value in the Mark−Houwink−Sakurada plot (0.15 acetone-soluble vs 0.33 acetone-insoluble). The differences in geometry were supported by the linkage analysis from NMR showing the acetone-soluble part containing fewer native linkages. In both of these examples, kraft lignin behaved like a solid sphere, limiting the ability to provide entanglements between molecular chains. From this standpoint, macroscopic properties of lignin are justified with this knowledge of a dense and extremely compact structure.

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Section: Introductionmentioning

confidence: 99%

Revisiting the Molar Mass and Conformation of Derivatized Fractionated Softwood Kraft Lignin

Liu

Cho

et al. 2021

Biomacromolecules

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“…For instance, HSQC signals assigned to α-O-alkyl linkages in lignin were more prominent under milder conditions than under severe conditions. These linkages together with 4-O-etherified 5-5′ linkages, which have been shown to constitute branching points in lignin 40,41 are more likely to survive hydrolysis under milder conditions, and hence branching at a high T g is observed for the D3 and D7 entries. The T g may then drop as the lignin becomes more linear through ether bond hydrolysis at intermediate temperatures (entry D13 and sample 160 °C, 1.5% acid) and then rise again on the onset of lignin repolymerization reactions as observed for D4 and D6 entries.…”

Section: Differential Scanning Calorimetrymentioning

confidence: 99%

“…The 5-5′ units are abundant in native spruce lignin. 40,41 Unlike arylether lin- S2 and S3. † kages, these 5-5′ linkages are stable under common processing conditions and may therefore constitute the majority of unquantified inter-units.…”

Section: Chemical and Physical Properties Of Lignin In Relation To Lignin Yieldmentioning

confidence: 99%

Protected lignin biorefining through cyclic extraction: gaining fundamental insights into the tuneable properties of lignin by chemometrics

et al. 2022

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“…Although the signals are still weak, compared to the MBL, they are slightly stronger. These 5-5′ linkages are both native and could be formed. , It can be assumed that during the organosolv extraction, some of the β-O-4′ linkages are cleaved, which leads to the formation of β- and phenoxy radicals. From the phenoxy radicals, C5 radicals emerge, which then couple to the 5-5′ condensed substructures.…”

Section: Resultsmentioning

confidence: 99%

Fundamental Insights on the Physical and Chemical Properties of Organosolv Lignin from Norway Spruce Bark

et al. 2022

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The interest in the bark and the attempt to add value to its utilization have increased over the last decade. By applying an integrated bark biorefinery approach, it is possible to investigate the recovery of compounds that can be used to develop green and sustainable alternatives to fossil-based materials. In this work, the focus is on extracting Norway spruce ( Picea abies ) bark lignin via organosolv extraction. Following the removal of the extractives and the subcritical water extraction to remove the polysaccharides, a novel cyclic organosolv extraction procedure was applied, which enabled the recovery of lignin with high quality and preserved structure. Main indicators for low degradation and preservation of the lignin structure were a high β-O-4′ content and low amounts of condensed structures. Furthermore, high purity and low polydispersity of the lignin were observed. Thus, the obtained lignin exhibits high potential for use in the direct development of polymer precursors and other bio-based materials. During the extraction sequence, around 70% of the bark was extracted. Besides the lignin, the extractives as well as pectic polysaccharides and hemicelluloses were recovered with only minor degradation, which could potentially be used for the production of biofuel or other high-value products such as emulsifiers or adhesives.

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Deciphering lignin heterogeneity in ball milled softwood: unravelling the synergy between the supramolecular cell wall structure and molecular events

Abstract: Mechanical milling of lignocellulose has been used in several studies as a key pretreatment enabling extraction of lignin from various sources for structural analysis. It is also applied as an...

Cited by 38 publications

References 38 publications

Revisiting the Molar Mass and Conformation of Derivatized Fractionated Softwood Kraft Lignin

Revisiting the Molar Mass and Conformation of Derivatized Fractionated Softwood Kraft Lignin

Protected lignin biorefining through cyclic extraction: gaining fundamental insights into the tuneable properties of lignin by chemometrics

Fundamental Insights on the Physical and Chemical Properties of Organosolv Lignin from Norway Spruce Bark

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