Biopolymer Lignin Research Articles

Formation of Nanodiamonds during Pyrolysis of Butanosolv Lignin.

The preparation of artificial diamonds has a long history driven by decreased costs compared to naturally occurring diamonds and ethical issues. However, fabrication of diamonds in the laboratory from readily available biomass has not been extensively investigated. This work demonstrates a convenient method for producing nanodiamonds from biopolymer lignin at ambient pressure. Lignin was extracted from Douglas Fir sawdust using a butanosolv pretreatment and was pyrolyzed in N2 at 1000 °C, followed by a second thermal treatment in 5% H2/Ar at 1050 °C, both at ambient pressure. This led to the formation of nanodiamonds embedded in an amorphous carbon substrate. The changes occurring at various stages of the pyrolysis process were monitored by scanning electron microscopy, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. High resolution transmission electron microscopy revealed that nanodiamond crystallites, 4 nm in diameter on average, formed via multiple nucleation events in some carbon-containing high density spheres. It is proposed that highly defected graphene-like flakes form during the pyrolysis of lignin as an intermediate phase. These flakes are more deformable with more localized π electrons in comparison with graphene and join together face-to-face in different manners to form cubic or hexagonal nanodiamonds. This proposed mechanism for the formation of nanodiamonds is relevant to the future fabrication of diamonds from biomass under relatively mild conditions.

Development of CuS/C composite for microwave absorption using lignin biopolymer

In recent decades, electronic devices have become a crucial component of everyday life and an increasingly important aspect of national security. However, despite their convenience, the emission of electromagnetic (EM) radiation from these devices has created a pollution issue that demands urgent attention. In this study, the properties and performance of CuS/C composites as EM wave-absorbing materials were examined. The main technique employed involved modifying the surface structure and properties of a lignin biopolymer via a fiber laser to derive porous carbon as a microwave absorber in the X-band range. Flower-like CuS microspheres were integrated into the porous carbon to improve the electrical conductivity and promote internal reflections. In addition, multilayer microwave absorbers were developed using CuS/C/epoxy composites with varying weight percentages, which were fabricated through refluxing and annealing techniques. The return losses of the absorbers in single- and multi-layer modes were optimized by modified local particle swarm optimization (MLPSO). The minimum average return loss improved to −15 dB (96.8%) by optimization in the 4-layer mode with a thickness of 1.8 mm. The optimum absorption peak in the 3-layer structure was −54.52 dB at a frequency of 8.83 GHz. The shielding effectiveness assessments indicated that the CuS/C/epoxy composite significantly improved the shielding capabilities of porous C and CuS, resulting in an increase of the shielding effectiveness threshold (SET) from less than 2 dB in lignin to more than 10 dB in CuS/C/epoxy.

Unveiling the mechanism of triphos-Ru catalysed C–O bond disconnections in polymers

Ruthenium complexes with facially coordinating tripodal phosphine ligands are privileged catalysts for a broad range of (de-)hydrogenation-based transformations. Among these, C–O bond hydrogenolysis holds potential for the depolymerisation of both the biopolymer lignin and epoxy resins applied in wind turbine blades, aircrafts and more. However, this methodology is poorly understood in mechanistic terms. Here, we present a detailed investigation on the triphos-Ru catalysed C–O bond scission on a molecular level. A combination of experimental, spectroscopical and theoretical studies elucidates the reactivity of the ruthenium trimethylenemethane precatalyst, revealing the key roles of ruthenium phenolates in both catalyst activation as well as the catalytic cycle itself. Furthermore, a Ru(0)/Ru(II) oxidative addition into the C–O bond is disclosed, with a triphos-Ru(0) dihydrogen complex as entry point. With the molecular nature of the operating triphos-Ru species and the thermodynamics and kinetics of the catalysis unravelled, improvements of established methods as well as design of related transformations may become possible.

The Impact of Lignin Biopolymer Sources, Isolation, and Size Reduction from the Macro- to Nanoscale on the Performances of Next-Generation Sunscreen.

In recent years, concerns about the harmful effects of synthetic UV filters on the environment have highlighted the need for natural sun blockers. Lignin, the most abundant aromatic renewable biopolymer on Earth, is a promising candidate for next-generation sunscreen due to its inherent UV absorbance and its green, biodegradable, and biocompatible properties. Lignin's limitations, such as its dark color and poor dispersity, can be overcome by reducing particle size to the nanoscale, enhancing UV protection and formulation. In this study, 100-200 nm lignin nanoparticles (LNPs) were prepared from various biomass by-products (hardwood, softwood, and herbaceous material) using an eco-friendly anti-solvent precipitation method. Pure lignin macroparticles (LMPs) were extracted from beech, spruce, and wheat straw using an ethanol-organosolv treatment and compared with sulfur-rich kraft lignin (KL). Sunscreen lotions made from these LMPs and LNPs at various concentrations demonstrated novel UV-shielding properties based on biomass source and particle size. The results showed that transitioning from the macro- to nanoscale increased the sun protection factor (SPF) by at least 2.5 times, with the best results improving the SPF from 7.5 to 42 for wheat straw LMPs and LNPs at 5 wt%. This study underscores lignin's potential in developing high-quality green sunscreens, aligning with green chemistry principles.

One-pot molten strategy to synthesize tough bio-derived lignin-based photothermal elastomers for photoelectric driven and programmable shape memory

Utilizing renewable biomass as an alternative to petroleum-based products for the development of smart materials emerges as a pivotal strategy for sustainable development. However, the straightforward, rapid, and cost-effective deployment of biomass for novel smart material synthesis remains a formidable challenge. Herein, we employ a facile solvent-free one-pot strategy to develop a multifunctional smart biomass photothermal elastomer, which synthesized from the natural small molecule of α-lipoic acid (LA) and renewable lignin biopolymer without any chemical modification. The incorporation of lignin confers to the obtained elastomers superior mechanical strength, photothermal responsiveness, photothermal self-healing, and adhesive capabilities. Notably, the photothermal elastomers can be fully recycled and reused by simple thermal remodeling. As a proof of concept, the temperature difference generator can be driven to generate electricity utilizing the excellent photothermal effect of elastomers, highlighting its excellent light-heat-electricity conversion capability. Intriguingly, the photothermal elastomers exhibit light-driven shape memory effect, enabling to grasp objects by shape-programmed four-arm soft gripper under selective irradiation. This pioneering work not only demonstrates significant progress in high-value utilization of bio-derived lignin, but also opens up a new avenue for sustainable and innovative applications in advanced energy management devices and soft actuators.

Novel sustainable corrosion inhibitors for enhancing carbon steel corrosion resistance based on clay and lignin biopolymer extracted from raw Alfa fibers

Novel sustainable corrosion inhibitors for enhancing carbon steel corrosion resistance based on clay and lignin biopolymer extracted from raw Alfa fibers

Characterization of vinyl ester–based biocomposites using grape stalk lignin biopolymer and Celosia cristata stem fibers: a characterization study

Characterization of vinyl ester–based biocomposites using grape stalk lignin biopolymer and Celosia cristata stem fibers: a characterization study

Mitigation of Soil Erosion and Enhancement of Slope Stability through the Utilization of Lignin Biopolymer.

Human activities have had a profound impact on the environment, particularly in relation to surface erosion and landslides. These processes, which are natural phenomena, have been exacerbated by human actions, leading to detrimental consequences for ecosystems, communities, and the overall health of the planet. The use of lignin (LIG) as a biopolymer soil additive material is regarded as an eco-friendly solution against soil erosion and slope failure which holds immense promise. However, significant research gaps currently hinder a comprehensive understanding of its mechanisms and effectiveness. Experimental studies offer a robust platform to address these gaps by providing controlled conditions for assessing soil stability, exploring mechanisms, and evaluating adaptability. Bridging these research gaps will contribute to the development of innovative and sustainable strategies for mitigating soil erosion and preventing slope failure, thereby promoting environmental resilience and resource conservation. This study aimed to investigate the effect of the LIG biopolymer on mitigation of soil erosion, slope failure and the enhancement of soil strength by conducting laboratory tests (UU triaxial, unconfined compressive strength (UCS), and soaking) as well as flume experiments under uniform rainfall events. The alterations in the engineering characteristics and erosion resistance of silty soil mixed with a LIG additive at concentrations of 1% and 3.0% by weight have been examined. The results show that the LIG-treated samples demonstrated an enhanced resistance to surface erosion and an enhanced prevention of slope failure, as well as improved shear stress, cohesion, stiffness, and resistance to water infiltration.

Dimensionally stable and durable wood by lignin impregnation

Cracking, warping, and decaying stemming from wood's poor dimensional stability and durability are the most annoying issues of natural wood. There is an urgent need to address these issues, of which, sustainable and green chemical treatments are favorably welcomed. Herein, we developed a facile method through the incorporation of environmentally friendly biopolymer lignin into wood cells for wood dimensional stability and durability enhancement. Enzymatic hydrolysis lignin (EHL) was dissolved into various solvents followed by impregnation and drying to incorporate lignin into wood cells. Impregnation treatment was developed to incorporate into wood to improve its dimensional stability, durability, and micromechanics. The anti-swelling efficiency reached up to 99.4 %, the moisture absorption decreased down to 0.55 %, the mass loss after brown rot decay decreased to 7.22 %, and the cell wall elasticity as well as hardness increased 8.7 % and 10.3 %, respectively. Analyses acquired from scanning electron microscopy, fluorescent microscopy, and Raman imaging revealed that the EHL was successfully colonized in cell lumen as well as in cell walls, thus improved wood dimensional stability and durability. Moreover, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed EHL interaction with the cell wall components, thus the wood mechanical property was not impaired significantly, whereas nanoindentation data indicated even slight mechanical enhancement on the cell walls. This facile approach can improve the wood properties in multiple aspects and remarkably enhance the outdoor performance of modified wood products. In addition, using lignin as a natural modifying agent to improve wood performance will have a great positive impact on the environment.

Efficient isomerization of glucose to fructose over Al-loaded functional lignin biopolymer

Al-loaded functional lignin biopolymer (Alx-Lbp) catalysts were synthesized using H2O2 oxidized alkali lignin and aluminum acetate via mechanochemical modification without post-calcination treatment. The Alx-Lbp catalysts exhibited higher hydrophilicity and lower surface energy than lignin-free Al-activated carbon catalysts. Unprecedented high yields (58.5 %) of fructose from glucose were obtained over Al1-Lbp in ethanol at 140 ºC in 30 min reaction time. Al1-Lbp catalyst had Lewis acid sites (47.2 μmol/g), Brønsted acid sites (6.9 μmol/g) and a surface energy of 39.1 mN/m that facilitated glucopyranose ring-opening and gave a glucose isomerization activation energy of 65.2 kJ/mol, which was lower than values reported for Lewis acid-catalyzed systems. Active sites of Al2O3 and Al(OH)3 formed on the Al1-Lbp catalyst in ethanol promoted the formation of an enediol intermediate as confirmed with isotope experiments to achieve efficient isomerization of glucose to fructose. The Al1-Lbp catalyst demonstrated recyclability and maintained its initial activity for eight times reuse.

Harnessing Atomically Dispersed Cobalt for the Reductive Catalytic Fractionation of Lignocellulose.

The reductive catalytic fractionation (RCF) of lignocellulose, considering lignin valorization at design time, has demonstrated the entire utilization of all lignocellulose components; however, such processes always require catalysts based on precious metals or high-loaded nonprecious metals. Herein, the study develops an ultra-low loaded, atomically dispersed cobalt catalyst, which displays an exceptional performance in the RCF of lignocellulose. An approximately theoretical maximum yield of phenolic monomers (48.3 wt.%) from lignin is realized, rivaling precious metal catalysts. High selectivity toward 4-propyl-substituted guaiacol/syringol facilitates their purification and follows syntheses of highly adhesive polyesters. Lignin nanoparticles (LNPs) are generated by simple treatment of the obtained phenolic dimers and oligomers. RCF-resulted carbohydrate pulp are more obedient to enzymatic hydrolysis. Experimental studies on lignin model compounds reveal the concerted cleavage of Cα-O and Cβ-O pathway for the rupture of β-O-4 structure. Overall, the approach involves valorizing products derived from lignin biopolymer, providing the opportunity for the comprehensive utilization of all components within lignocellulose.

Retraction Note: Recent advances and future perspectives of lignin biopolymers

Retraction Note: Recent advances and future perspectives of lignin biopolymers

Eco-friendly conversion between n- and p-type carbon nanotubes based on rationally functionalized lignin biopolymers

We strategically modify lignin as effective p- and n-dopants for nanocarbon materials, offering promising alternatives to chemical dopants from fossil-fuels.

Assessment of the effect of lignin biopolymer on the thermal stability of energetic nitrocellulose/diethylene glycol dinitrate composite

AbstractThis study explored the stability and thermo‐kinetic features of double base nitrocellulose (NC)/diethylene glycol dinitrate (DEGDN) propellant supplemented with Kraft lignin. For this purpose, the impact of 2‐nitrodiphenylamine (2‐NDPA), 1,3‐dimethyl‐1,3‐diphenylurea (C‐II) and lignin stabilizers on the molecular structure, morphology, and thermokinetic behavior of NC/DEGDN composite were thoroughly analyzed. Experimental results showed that lignin exhibits promising stabilizing efficiency comparable to that of the conventional 2‐NDPA and C‐II. In addition, thermal findings highlighted that the incorporation of 2‐NDPA, C‐II, and lignin has improved the thermal decomposition temperature of NC/DEGDN propellant. The investigation of the thermolysis kinetics of stabilized NC/DEGDN composites demonstrated an increase in the Arrhenius parameters with respect to the NC/DEGDN baseline. Above all, this investigation contributes to the ongoing efforts to develop new environmentally friendly stabilizers for nitrate esters‐based composites.

The Covalent Linking of Organophosphorus Heterocycles to Date Palm Wood-Derived Lignin: Hunting for New Materials with Flame-Retardant Potential

Environmentally acceptable and renewably sourced flame retardants are in demand. Recent studies have shown that the incorporation of the biopolymer lignin into a polymer can improve its ability to form a char layer upon heating to a high temperature. Char layer formation is a central component of flame-retardant activity. The covalent modification of lignin is an established technique that is being applied to the development of potential flame retardants. In this study, four novel modified lignins were prepared, and their char-forming abilities were assessed using thermogravimetric analysis. The lignin was obtained from date palm wood using a butanosolv pretreatment. The removal of the majority of the ester groups from this heavily acylated lignin was achieved via alkaline hydrolysis. The subsequent modification of the lignin involved the incorporation of an azide functional group and copper-catalysed azide–alkyne cycloaddition reactions. These reactions enabled novel organophosphorus heterocycles to be linked to the lignin. Our preliminary results suggest that the modified lignins had improved char-forming activity compared to the controls. 31P and HSQC NMR and small-molecule X-ray crystallography were used to analyse the prepared compounds and lignins.

Lignin Modification for Enhanced Performance of Polymer Composites.

The biopolymer lignin, which is heterogeneous and abundant, is usually present in plant cell walls and gives them rigidity and strength. As a byproduct of the wood, paper, and pulp manufacturing industry, lignin ranks as the second most prevalent biopolymer worldwide, following cellulose. This review paper explores the extraction, modification, and prospective applications of lignin in various industries, including the enhancement of thermosetting and thermoplastic polymers, biomedical applications such as vanillin production, fuel development, carbon fiber composites, and the creation of nanomaterials for food packaging and drug delivery. The structural characteristics of lignin remain undefined due to its origin, separation, and fragmentation processes. This comprehensive overview encompasses state-of-the-art techniques, potential applications, diverse extraction methods, chemical modifications, carbon fiber utilization, and the extraction of vanillin. Moreover, the review focuses on the utilization of lignin-modified polymer blends across multiple manufacturing sectors, providing insights into the advantages and limitations of this innovative approach for the development of environmentally friendly materials.

Green and Low-Cost Alkali-Polyphenol Synergetic Self-Catalysis System Access to Fast Gelation of Self-Healable and Self-Adhesive Conductive Hydrogels for Self-Powered Triboelectric Nanogenerators.

Biomass-based hydrogels have attracted great attention in flexible and sustainable self-powered power sources but struggled to fabricate in a green, high-efficiency, and low-cost manner. Herein, a novel and facile alkali-polyphenol synergetic self-catalysis system is originally employed for the fast gelation of self-healable and self-adhesive lignin-based conductive hydrogels, which can be regarded as hydrogel electrodes of flexible triboelectric nanogenerators (TENGs). This synergy self-catalytic system comprises aqueous alkali and polyphenol-containing lignin, in which alkali-activated ammonium persulfate (APS) significantly accelerates the generation of radicals and initiates the polymerization of monomers, while polyphenol acts as a stabilizer to avoid bursting polymerization from inherent radical scavenging ability. Furthermore, multiple hydrogen bonds between lignin biopolymers and polyacrylamide (PAM) chains impart lignin-based hydrogels with exceptional adhesiveness and self-healing properties. Intriguingly, the alkaline conditions not only contribute to the solubility of lignin but also impart superior ionic conductivity of lignin-based hydrogel that is applicable to flexible TENG in self-powered energy-saving stair light strips, which holds great promise for industrial applications of soft electronics.

Organosolv Pretreatment of Cocoa Pod Husks: Isolation, Analysis, and Use of Lignin from an Abundant Waste Product.

Cocoa pod husks (CPHs) represent an underutilized component of the chocolate manufacturing process. While industry's current focus is understandably on the cocoa beans, the husks make up around 75 wt % of the fruit. Previous studies have been dominated by the carbohydrate polymers present in CPHs, but this work highlights the presence of the biopolymer lignin in this biomass. An optimized organosolv lignin isolation protocol was developed, delivering significant practical improvements. This new protocol may also prove to be useful for agricultural waste-derived biomasses in general. NMR analysis of the high quality lignin led to an improved structural understanding, with evidence provided to support deacetylation of the lignin occurring during the optimized pretreatment. Chemical transformation, using a tosylation, azidation, copper-catalyzed click protocol, delivered a modified lignin oligomer with an organophosphorus motif attached. Thermogravimetric analysis was used to demonstrate the oligomer's potential as a flame-retardant. Preliminary analysis of the other product streams isolated from the CPHs was also carried out.

Sustainable Biomass Lignin-Based Hydrogels: A Review on Properties, Formulation, and Biomedical Applications.

Different techniques have been developed to overcome the recalcitrant nature of lignocellulosic biomass and extract lignin biopolymer. Lignin has gained considerable interest owing to its attractive properties. These properties may be more beneficial when including lignin in the preparation of highly desired value-added products, including hydrogels. Lignin biopolymer, as one of the three major components of lignocellulosic biomaterials, has attracted significant interest in the biomedical field due to its biocompatibility, biodegradability, and antioxidant and antimicrobial activities. Its valorization by developing new hydrogels has increased in recent years. Furthermore, lignin-based hydrogels have shown great potential for various biomedical applications, and their copolymerization with other polymers and biopolymers further expands their possibilities. In this regard, lignin-based hydrogels can be synthesized by a variety of methods, including but not limited to interpenetrating polymer networks and polymerization, crosslinking copolymerization, crosslinking grafted lignin and monomers, atom transfer radical polymerization, and reversible addition-fragmentation transfer polymerization. As an example, the crosslinking mechanism of lignin-chitosan-poly(vinyl alcohol) (PVA) hydrogel involves active groups of lignin such as hydroxyl, carboxyl, and sulfonic groups that can form hydrogen bonds (with groups in the chemical structures of chitosan and/or PVA) and ionic bonds (with groups in the chemical structures of chitosan and/or PVA). The aim of this review paper is to provide a comprehensive overview of lignin-based hydrogels and their applications, focusing on the preparation and properties of lignin-based hydrogels and the biomedical applications of these hydrogels. In addition, we explore their potential in wound healing, drug delivery systems, and 3D bioprinting, showcasing the unique properties of lignin-based hydrogels that enable their successful utilization in these areas. Finally, we discuss future trends in the field and draw conclusions based on the findings presented.

Molecular insights into the evolution of woody plant decay in the gut of termites.

Plant cell walls represent the most abundant pool of organic carbon in terrestrial ecosystems but are highly recalcitrant to utilization by microbes and herbivores owing to the physical and chemical barrier provided by lignin biopolymers. Termites are a paradigmatic example of an organism's having evolved the ability to substantially degrade lignified woody plants, yet atomic-scale characterization of lignin depolymerization by termites remains elusive. We report that the phylogenetically derived termite Nasutitermes sp. efficiently degrades lignin via substantial depletion of major interunit linkages and methoxyls by combining isotope-labeled feeding experiments and solution-state and solid-state nuclear magnetic resonance spectroscopy. Exploring the evolutionary origin of lignin depolymerization in termites, we reveal that the early-diverging woodroach Cryptocercus darwini has limited capability in degrading lignocellulose, leaving most polysaccharides intact. Conversely, the phylogenetically basal lineages of "lower" termites are able to disrupt the lignin-polysaccharide inter- and intramolecular bonding while leaving lignin largely intact. These findings advance knowledge on the elusive but efficient delignification in natural systems with implications for next-generation ligninolytic agents.