| 1. |
- Esakkimuthu, Esakkiammal Sudha, et al.
(författare)
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Elucidating intermolecular forces to improve compatibility of kraft lignin in poly(lactic acid)
- 2024
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Ingår i: Frontiers in Chemistry. - 2296-2646. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Owing to its abundant supply from renewable resources, lignin has emerged as a promising functional filler for the development of sustainable composite materials. However, achieving good interfacial compatibility between lignin and synthetic polymers, particularly poly (lactic acid) (PLA), remains a fundamental challenge. To advance the development of high-performance bio-based composites incorporating lignin and PLA, our study has scrutinized to unravel the nuances of interfacial binding interactions with the lignin and PLA composite system. Molecular level and experimental examinations were employed to decipher fundamental mechanisms governing and demonstrating the interfacial adhesion. We synthesized casted films of lignin/PLA and acetylated lignin/PLA at varying weight percentages of lignin (5%, 10%, and 20%) and comprehensively investigated their physicochemical and mechanical properties. The inclusion of acetylated lignin in the composites resulted in improved mechanical strength and Young’s modulus, while the glass transition temperature and melting point were reduced compared to neat PLA. Systematic variations in these properties revealed distinct compatibility behaviors between unmodified lignin and acetylated lignin when incorporated into PLA. Molecular dynamics (MD) simulation results elucidated that the observed changes in material properties were primarily attributed to the acetylation of lignin. Acetylated lignin exhibited lower Coulombic interaction energy and higher van der Waals forces, indicating a stronger affinity to PLA and a reduced propensity for intermolecular aggregation compared to unmodified lignin. Our findings highlight the critical role of controlling intermolecular interactions and lignin aggregation to develop PLA composites with predictable performance for new applications, such as functional packaging materials.
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| 2. |
- Liu, Jinrong, 1995-
(författare)
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Lignin nanoparticles for photonic crystals and photothermal films
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of sustainable materials from biobased resources is essential due to environmental concerns posed by fossil-based materials. Lignin is a chemically complex biopolymer that exists in woody tissues of vascular plants. Lignin has many useful properties such as antioxidant activity, thermal stability, UV-absorbance, rigidity and so on. However, an inherent challenge of lignin relates to its complex molecular structures and poor solubility in water and common solvents. One strategy to utilize lignin is to fabricate lignin nanoparticles (LNP) that produce colloidally stable dispersions in water. This thesis aims to develop LNP-based materials which can be used in photonic crystals and photothermal films towards energy-efficient functional materials.The first part of the thesis focused on elucidation of the phenomena occurring during centrifugation-assisted assembly of LNP-photonic crystal (L-PC). L-PC with rainbow coloration or separate colors were produced by controlling the polydispersity index (PDI), particle size (150 to 240 nm), and assembly of LNPs. In a follow-up work, an improved method was developed to increase the yield of L-PCs. The effects of factors such as initial lignin concentration, and dilution time on the particle size and PDI of formed LNPs were studied. Empirical models were established to predict the size of LNPs and successfully used to control the resulting color of L-PCs. Moreover, the nanostructure of L-PCs was investigated. To harness lignin’s ability to absorb solar energy (light wavelength: 250–2500 nm), LNP-based composite films and coatings with photothermal performance were developed in the second part of the thesis. LNP-chitosan films and coatings were prepared and applied to indoor heat management. The LNPs content was adjusted from 10 to 40 wt%. By incorporating LNPs, the mechanical strength and photothermal properties of the films were improved compared to the pure chitosan film. Moreover, LNP-silver-chitosan (CC-Ag@LNP) films were prepared by using LNPs as a reducing agent. Silver ions were reduced on the surface of LNPs with UV-light assistance, and the hybrid nanoparticles were used to prepare films by casting. The CC-Ag@LNP films exhibited improved wet-strength and exhibited antibacterial performance against Escherichia coli (sterilization effect > 99.9%).Overall, this thesis contributes to both the fundamental insight in lignin aggregation to colloidal particles and showcases ways to control their assembly and incorporation into macroscopic materials with added functionality.
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| 3. |
- Morsali, Mohammad, 1992-
(författare)
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Site-specific reactions of softwood kraft lignin for biobased vitrimers and reactive colloidal particles
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lignin, a natural polyphenolic compound of wood, holds promise as a green alternative to fossil resources given the current environmental concerns. However, its complex structure and limited usability have impeded widespread use of lignin in biobased materials. This thesis is focused on employing a series of chemistries and techniques that facilitate lignin utilization in a variety of applications ranging from bulk materials to colloidal particles. Lignin-based vitrimers, developed by a one pot, catalyst-free click addition of poly(ethylene glycol) divinyl ether to softwood kraft lignin and formation of dynamic acetal exchange network showed excellent performance as recoverable adhesives, reaching lab shear strengths of 2.6 MPa and 6.0 MPa for wood and aluminum substrates, respectively. Stabilized lignin nanoparticles synthesized by hydrothermal crosslinking of hydroxymethylated lignin nanoparticles showed an excellent colloidal stability in organic solvents such as ethanol, acetone, dimethylformamide, and tetrahydrofuran, and aqueous media (3 < pH < 12). These stabilized lignin nanoparticles were subjected to direct surface modification in colloidal state to develop aminated pH-responsive particles. Stabilized lignin nanoparticles, preserving redox activity, showed a capacity in reducing silver ions, forming hybrid lignin-silver nanoparticles for applications such as hydrogen peroxide colloidal sensors. Interaction of silver ions and stabilized lignin nanoparticles contributed to the emergence of discrete patterns of silver in lignin nanoparticle embedded hydrogels. The location and distance of the discrete patterns can be modified by altering the particle size and concentration. Furthermore, redox activity of stabilized lignin nanoparticles, hydroxymethylated lignin nanoparticles and unmodified lignin nanoparticles with different particle sizes (90 nm, 150 nm, 640 nm) were studied in charge storage applications in organic poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) electrodes. Non-modified lignin nanoparticles with the diameter of 150 nm showed the best performance overall, with specific capacities of the electrode reaching 42.5 mAh/g at a current density of 1 A/g. These particles were also demonstrated in a Zinc-lignin battery prototype. To further explore and broaden the horizon of lignin applications, propargylated lignin nanoparticles demonstrated light-induced “click” reactions initiated thermally or by Cu (I) or energy-efficient light emitting diodes with 405 nm wavelength. These nanoparticles were further employed to demonstrate the light-triggered reactions with betulin azide in Pickering emulsions, showcasing the versatility of colloidal chemistry of lignin and opportunities for new applications.
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| 4. |
- Rossato, Letizia Anna Maria, et al.
(författare)
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Phospholipase D Immobilization on Lignin Nanoparticles for Enzymatic Transformation of Phospholipids
- 2024
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Ingår i: ChemSusChem. - 1864-5631 .- 1864-564X. ; 17:3
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Tidskriftsartikel (refereegranskat)abstract
- Lignin nanoparticles (LNPs) are promising components for various materials, given their controllable particle size and spherical shape. However, their origin from supramolecular aggregation has limited the applicability of LNPs as recoverable templates for immobilization of enzymes. In this study, we show that stabilized LNPs are highly promising for the immobilization of phospholipase D (PLD), the enzyme involved in the biocatalytic production of high-value polar head modified phospholipids of commercial interest, phosphatidylglycerol, phosphatidylserine and phosphatidylethanolamine. Starting from hydroxymethylated lignin, LNPs were prepared and successively hydrothermally treated to obtain c-HLNPs with high resistance to organic solvents and a wide range of pH values, covering the conditions for enzymatic reactions and enzyme recovery. The immobilization of PLD on c-HLNPs (PLD-c-HLNPs) was achieved through direct adsorption. We then successfully exploited this new enzymatic preparation in the preparation of pure polar head modified phospholipids with high yields (60–90 %). Furthermore, the high stability of PLD-c-HLNPs allows recycling for a number of reactions with appreciable maintenance of its catalytic activity. Thus, PLD-c-HLNPs can be regarded as a new, chemically stable, recyclable and user-friendly biocatalyst, based on a biobased inexpensive scaffold, to be employed in sustainable chemical processes for synthesis of value-added phospholipids.
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| 5. |
- Zheng, Yong, et al.
(författare)
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Harnessing chemical functionality of lignin towards stimuli-responsive materials
- 2024
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Ingår i: Trends in chemistry. - 2589-7209 .- 2589-5974. ; 6:2, s. 62-78
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Forskningsöversikt (refereegranskat)abstract
- The mysteries of chemical structures and properties of lignin are gradually being unveiled. In parallel, lignin is gaining ground as a versatile resource for the development of stimuli-responsive materials with environmentally friendly, high-performance, and multifunctional characters. This review focuses on synthesis and mechanisms of lignin-based stimuli-responsive materials, highlighting the chemical structures linked to responses to various different stimuli, such as pH and temperature. We also highlight applications of these materials in drug carriers, bioimaging, shape memory, strain sensors, and substance detection, with the objective to showcase the untapped potential of lignin, challenging the prevailing notion that lignin is merely a by-product of the pulp industry. Finally, we identify challenges and propose future directions for the development of lignin-based stimuli-responsive materials.
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