Microwave processing of lignin in green solvents: A high-yield process to narrow-dispersity oligomers

Cederholm, Linnea; Xu, Yunsheng; Tagami, Ayumu; Sevastyanova, Olena; Odelius, Karin; Hakkarainen, Minna

doi:10.1016/j.indcrop.2020.112152

Cited by 26 publications

(35 citation statements)

References 53 publications

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“…The M w for the spruce and eucalyptus lignin fractions are given in Tables S1 and S2. The chemical composition, functional group content (as determined by 31 P NMR spectroscopy), thermal properties, and other properties of the fractionated lignins can be found elsewhere …”

Section: Methodsmentioning

confidence: 99%

New Insight into the Surface Structure of Lignin Nanoparticles Revealed by ¹H Liquid-State NMR Spectroscopy

Pylypchuk

Lindén

Lindström

et al. 2020

ACS Sustainable Chem. Eng.

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1 H liquid-state nuclear magnetic resonance (NMR) spectroscopy was applied for the first time to lignin nanoparticles (LNPs) in an aqueous suspension to study the surface composition of LNPs and to acquire a better understanding of the mechanism of their formation. A series of LNPs were prepared from spruce and eucalyptus kraft lignin fractions with narrow molecular weight distributions and functionalities. An NMR pulse program combining presaturation with excitation sculpting increased the signal resolution, making it possible to observe a superficial layer of LNPs directly in the aqueous suspension, "as prepared". The particle size, charge, and surface morphology were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). According to liquid-state NMR, methoxy groups from syringyl and guaiacyl units of lignin are the main groups present on the surface of LNPs. The presence of aliphatic moieties, mainly from side chains of lignin molecules, has also been confirmed. Taking into consideration the chemical composition of the lignin fractions, the structure of lignin NPs as shown by NMR spectroscopy and their size and surface charge, a pattern of lignin self-assembly into LNPs has been suggested.

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Section: Methodsmentioning

confidence: 99%

New Insight into the Surface Structure of Lignin Nanoparticles Revealed by ¹H Liquid-State NMR Spectroscopy

Pylypchuk

Lindén

Lindström

et al. 2020

ACS Sustainable Chem. Eng.

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“…To resolve this issue, technical lignin can be fractionated and chemically modified by various approaches. In order to control the molecular weight distribution and polydispersity, various fractionation methodologies, such as membrane filtration, sequential precipitation, solvent screening, or microwave processing, can be applied. − Another approach is to degrade the technical lignin into monomeric units with subsequent purification and retrieval, for example, vanillin and other derivatives. , Utilization of lignin as an aromatic source for polymers can thus be achieved in several different ways. Extensive work has, for example, been done on modifying vanillin for polymer use .…”

Section: Introductionmentioning

confidence: 99%

Exploring the Effects of Different Cross-Linkers on Lignin-Based Thermoset Properties and Morphologies

Ribca

Jawerth

Brett

et al. 2021

ACS Sustainable Chem. Eng.

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The search for sustainable material solutions has put lignin as one of the prime candidates for aromatic building blocks in macromolecular materials. The present study aimed to demonstrate how lignin-based thermoset resins can be utilized in combination with different cross-linkers. Kraft lignin was used to produce thermosets with tunable mechanical and morphological properties. The lignin-based thermosets were obtained via a thermally induced thiol−ene reaction. The first part of this work was focused on Kraft lignin solvent fractionation and chemical modification of the ethanol soluble fraction. Chemical analysis indicated that the allylation process was selective toward phenolic hydroxyl groups. SAXS and SEM studies demonstrated that solvent fractionation and allylation processes affected the molecular and nanoscale morphological characteristics of lignin. The second part's focus was on how the properties of thermosets can be tuned by using three different cross-linkers. The dynamic mechanical and morphological properties of three different thermosets were investigated via DMA, SAXS, and WAXS techniques. The three different thermosets exhibit similar molecular morphology but different storage modulus and glass transition temperature. In this work, it was shown that despite lignin's heterogeneity it was possible to produce thermosetting materials with tunable properties.

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“…The heterogeneous nature of lignin poses challenges for effective utilization in high-value applications . To illustrate, fractionation and extraction processes have been utilized for the preparation of more homogeneous and well-defined lignin materials. , …”

Section: Introductionmentioning

confidence: 99%

Microwave Hydrophobized Lignin with Antioxidant Activity for Fused Filament Fabrication

Yao

Odelius

Hakkarainen

2021

ACS Appl. Polym. Mater.

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The poor compatibility and aggregation propensity of lignin in nonpolar polymer matrices greatly limits its application in polymer blends and composites. We demonstrate an efficient, solvent-free, and catalyst-free microwave-assisted approach for hydrophobization of alkali lignin to enhance its compatibility with polylactide. Effective modification with up to 98% substitution of lignin’s hydroxyl groups was achieved under mild and catalyst-free reaction conditions. The modified acetylated and hexanoated lignins exhibited enhanced thermal stability and thermoplasticity, which were reflected by the good melt-extrusion and 3D printing properties of the corresponding polylactide/lignin blends. The tensile properties varied somewhat depending on the degree and type of substitution and the amount of hydrophobized lignin but in general the tensile properties were in the same range as those of polylactide. Blends consisting of up to 50 weight-% acetylated lignin were successfully extruded to filaments and 3D printed, demonstrating good processability and tensile properties regardless of the high lignin content, while it was not possible to extrude continuous filaments of polylactide and nonmodified alkali lignin even at low concentration (10 weight %). Additionally, the polylactide/acetylated lignin blends exhibited antioxidant activity as revealed by radical scavenging ability and improved thermo-oxidative stability with up to 40 °C increase in oxidation induction temperature compared to neat polylactide. The sustainable compatibilization strategy proposed herein paves the way for value-added utilization of lignin in fully biobased 3D printing filaments with improved oxidative stability.

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Microwave processing of lignin in green solvents: A high-yield process to narrow-dispersity oligomers

Cited by 26 publications

References 53 publications

New Insight into the Surface Structure of Lignin Nanoparticles Revealed by ¹H Liquid-State NMR Spectroscopy

New Insight into the Surface Structure of Lignin Nanoparticles Revealed by ¹H Liquid-State NMR Spectroscopy

Exploring the Effects of Different Cross-Linkers on Lignin-Based Thermoset Properties and Morphologies

Microwave Hydrophobized Lignin with Antioxidant Activity for Fused Filament Fabrication

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Microwave processing of lignin in green solvents: A high-yield process to narrow-dispersity oligomers

Cited by 26 publications

References 53 publications

New Insight into the Surface Structure of Lignin Nanoparticles Revealed by 1H Liquid-State NMR Spectroscopy

New Insight into the Surface Structure of Lignin Nanoparticles Revealed by 1H Liquid-State NMR Spectroscopy

Exploring the Effects of Different Cross-Linkers on Lignin-Based Thermoset Properties and Morphologies

Microwave Hydrophobized Lignin with Antioxidant Activity for Fused Filament Fabrication

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Product

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New Insight into the Surface Structure of Lignin Nanoparticles Revealed by ¹H Liquid-State NMR Spectroscopy

New Insight into the Surface Structure of Lignin Nanoparticles Revealed by ¹H Liquid-State NMR Spectroscopy