The high glass transition temperature (Tg), stiffness, and poor flow properties of lignin are obstacles to lignin and lignocellulose utilization in thermoplastic applications. Two commonly applied methods to modify the viscoelastic properties of polymers are external plasticization, which involves physically blending them with low-molecular-weight additives, and internal plasticization, which involves covalently attaching side chains. However, most studies on lignin plasticization have focused on either technical, low-molecular-weight lignin or native, in situ lignin, with few efforts to bridge this gap. This study aims to determine if different lignin structures are susceptible to different modes of plasticization and how the plasticizer affects the phase morphology of the blends. Four lignins (softwood kraft lignin and lignin isolated from wheat straw, Norway spruce xylem, and residual softwood kraft pulp lignin) were plasticized with three external plasticizers (glycerol, triacetin, and diethyl phthalate) with different functionalities. The four lignins were in parallel internally plasticized by esterification with short-chain fatty acids (acetic, propionic, and butyric acid). The Tg and phase morphology of the modified lignins were studied by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Apart from phase separation in some lignin plasticizer blends, each plasticizer demonstrated similar efficiency (Tg depression) across all lignins, suggesting that the structure of the plasticizer, rather than the lignin structure, plays a more significant role in determining the outcome. Aprotic plasticizers were generally more efficient than protic per molar unit, and the magnitude of their mechanical dampening was also smaller over the glass transition, likely due to a decrease in the hydrogen bond density of the system. External plasticization was also found to narrow the width of the glass transition, indicating the formation of a morphologically more homogeneous material with less local Tgs than the pure lignin, whereas esterification broadened it somewhat.

Abstract [en]The macroalga Ulva fenestrata plays a key role in marine ecosystems and has increasing potential in aquaculture. However, its three-dimensional tissue architecture remains underexplored. This study applies multimodal fluorescence microscopy combined with optotracing to spatially map biopolymers and structural features in native Ulva tissue. Using Carbotrace 680, cellulose was localized in situ within the cell walls, while oligo/polyaromatic compounds were visualized across multiple scaffold layers via autofluorescence. Lambda scanning validated the fluorescence detection settings for cellulose (Exitation wavelength (Ex.) 561 nm, Emission wavelength (Em.) 570–631 nm), oligo/polyaromatics (Ex. 405 nm, Em. 408–505 nm), and chlorophyll (Ex. 639 nm, Em. 649–693 nm). Spatially resolved biopolymer anatomy maps were generated for blade and rhizoidal tissues, and 3D tissue models were constructed. The outermost blade layer exhibited a sandwich-like architecture, and a previously undescribed median layer was identified separating the two cell layers. This layer was >11 times thicker in rhizoidal tissue than in blade tissue, comprising 56 % and 7 % of the total thickness, respectively. Spectral differences in rhizoidal cells indicated cellular heterogeneity. Collectively, the observed biopolymer and architectural differences may reflect tissue-specific functional specialization of the macroalga. This imaging-based approach provides new perspectives on algal biology and supports the multisectoral valorization of Ulva.

The strive toward sustainability increases the demand for bio-based material production, forcing expansion of the biorefinery feedstock supply from forest wood to non-woody materials such as agricultural residues. As a model organism for legume crops, the aptness of agricultural lupins as a lignocellulose feedstock is investigated. Principle chemical analysis combined with optotracing, in which the fluorescent tracer molecule Carbotrace 680 generates a visual map of the native tissues’ lignocellulose anatomy at sub-cellular resolution, enables informed design of a mild recovery process. A streamlined conversion approach is then designed, yielding lignin-containing microfibrillated cellulose. By monitoring defibrillation and delignification throughout the extraction process, the use of optotracing for non-destructive fiber analytics at unprecedented details across all hierarchical structures of lignocellulosic materials is demonstrated. This crop valorization is a prime illustration of a holistic use of lupin biomass, with seeds serving as plant-based food sources, and other parts as sources for lignocellulose-based materials, thereby expanding both the biorefinery concept and feedstock supply.

The oxidation of cellulose to dialdehyde cellulose (DAC) is a process that has received increased interest during recent years. Herein, kinetic modeling of the reaction with sodium periodate as an oxidizing agent was performed to quantify rate-limiting steps and overall kinetics of the cellulose oxidation reaction. Considering a pseudo-first-order reaction, a general rate expression was derived to elucidate the impact of pH, periodate concentration, and temperature on the oxidation of cellulose and concurrent formation of cellulose degradation products. Experimental concentration profiles were utilized to determine the rate constants for the formation of DAC (k1), degradation constant of cellulose (k2), and degradation of DAC (k3), confirming that the oxidation follows a pseudo-first-order reaction. Notably, the increase in temperature has a more pronounced effect on k1 compared to the influence of IO4− concentration. In contrast, k2 and k3 display minimal changes in response to IO4− concentration but increase significantly with increasing temperature. The kinetic model developed may help with understanding the rate-limiting steps and overall kinetics of the cellulose oxidation reaction, providing valuable information for optimizing the process toward a faster reaction with higher yield of the target product.

The glass transition temperatures ( T g ) of native, residual, and technical lignins are important to lignocellulose pulping, pulp processing and side stream utilization; however, how the structural changes from native to residual and technical lignin influences T g has proven difficult to elucidate. Since the T g of macromolecules is greatly influenced by the molecular weight, low-molecular-weight fractions, such as milled wood lignin (MWL), are poor representatives of lignin in the cell wall. To circumvent this problem, lignins of both high yield and purity were isolated from Norway spruce and softwood kraft pulp using the enzymatic mild acidolysis lignin (EMAL) protocol. Technical softwood kraft lignin was also fractionated into groups of different molecular weights, to acquire lignin that spanned over a wide molecular-weight range. A powder sample holder for dynamic mechanical analysis (DMA), was used to determine the T g of lignins, for which calorimetric methods were not sensitive enough. The T g s of EMAL were found to be closer to their in situ counterparts than MWL.

A sustainable and efficient multicatalytic chemical transformation approach is devised for the development of all-biobased environmentally adaptable polymers and gels with multifunctional properties. The catalytic system, utilizing Lignin aluminum nanoparticles (AlNPs)-aluminum ions (Al³⁺), synergistically combines multiple catalytic cycles to create robust, mechanically stable, and versatile organohydrogels. Single catalytic cycles alone fail to achieve desired results, highlighting the importance of cooperatively combining different cycles for successful outcomes. The transformation involves free radical crosslinking, reversible quinone-catechol reactions, and an autocatalytic mechanism, resulting in a dual crosslinking strategy that incorporates both covalent and ionic crosslinking. This approach creates a dynamic gel system with combined energy dissipation and storage mechanisms. The engineered organohydrogels demonstrate vital multifunctionalities such as good thermal stability, self-healing, and adhesive properties, flame-retardancy, mechanical resilience and durability, conductivity, viscoelastic properties, environmental adaptability, and resistance to extreme conditions such as freezing and drying. The developed catalytic technology and resulting gels hold significant potential for applications in flexible electronics, energy storage, actuators, and sensors.

The search for new energy sources together with the need to control greenhouse gas emissions has led to continued interest in low-emitting renewable energy technologies. In this context, water splitting for hydrogen production is a reasonable alternative to replace fossil fuels due to its high energy density producing only water during combustion. Cellulose is abundant in nature and as residuals from human activity, and therefore a natural, ecological, and carbon-neutral source for hydrogen production. In the present work, we propose a sustainable method for hydrogen production using sunlight and cellulose as sacrificial agents during the photocatalytic water splitting process. Platinum (Pt) catalyst activates hydrogen production, and parameters such as pH of the system, cellulose concentration, and Pt loading were studied. Using different biomasses, we found that the presence of hemicellulose and xyloglucan as part of the molecular composition considerably increased the H-2 production rate from 36 mu mol L-1 in one hour for rapeseed cellulose to 167.44 mu mol L-1 for acid-treated cellulose isolated from Ulva fenestrata algae. Carboxymethylation and TEMPO-oxidation of cellulosic biomass both led to more stable suspensions with higher rates of H-2 production close to 225 mu mol L-1, which was associated with their water solubility properties. The results suggest that cellulosic biomass can be an attractive alternative as a sacrificial agent for the photocatalytic splitting of water for H-2 production.

The production and engineering of sustainable materials through green chemistry will have a major role in our mission of transitioning to a more sustainable society. Here, combined catalysis, which is the integration of two or more catalytic cycles or activation modes, provides innovative chemical reactions and material properties efficiently, whereas the single catalytic cycle or activation mode alone fails in promoting a successful reaction. Polyphenolic lignin with its distinctive structural functions acts as an important template to create materials with versatile properties, such as being tough, antimicrobial, self-healing, adhesive, and environmentally adaptable. Sustainable lignin-based materials are generated by merging the catalytic cycle of the quinone-catechol redox reaction with free radical polymerization or oxidative decarboxylation reaction, which explores a wide range of metallic nanoparticles and metal ions as the catalysts. In this review, we present the recent work on engineering lignin-based multifunctional materials devised through combined catalysis. Despite the fruitful employment of this concept to material design and the fact that engineering has provided multifaceted materials able to solve a broad spectrum of challenges, we envision further exploration and expansion of this important concept in material science beyond the catalytic processes mentioned above. This could be accomplished by taking inspiration from organic synthesis where this concept has been successfully developed and implemented.

Stimuli-responsive materials with reversible supramolecular networks controlled by a change in temperature are of interest in medicine, biomedicine and analytical chemistry. For these materials to become more impactful, the development of greener synthetic practices with more sustainable solvents, lower energy consumption and a reduction in metallic catalysts is needed. In this work, we investigate the polymerisation of N-acryloyl glycinamide monomer by single-electron transfer reversible-deactivation radical polymerisation and its effect on the cloud point of the resulting PNAGA polymers. We accomplished 80% conversion within 5 min in water media using a copper wire catalyst. The material exhibited a sharp upper critical solution temperature (UCST) phase transition (10–80% transition within 6 K). These results indicate that UCST-exhibiting PNAGA can be synthesized at ambient temperatures and under non-inert conditions, eliminating the cost- and energy-consuming deoxygenation step. The choice of copper wire as the catalyst allows the possibility of catalyst recycling. Furthermore, we show that the reaction is feasible in a simple vial which would facilitate upscaling.

The sustainable production of polymers and materials derived from renewable feedstocks such as biomass is vital to addressing the current climate and environmental challenges. In particular, finding a replacement for current widely used curable resins containing undesired components with both health and environmental issues, such as bisphenol-A and styrene, is of great interest and vital for a sustainable society. In this work, we disclose the preparation and fabrication of an all-biobased curable resin. The devised resin consists of a polyester component based on fumaric acid, itaconic acid, 2,5-furandicarboxylic acid, 1,4-butanediol, and reactive diluents acting as both solvents and viscosity enhancers. Importantly, the complete process was performed solvent-free, thus promoting its industrial applications. The cured biobased resin demonstrates very good thermal properties (stable up to 415 °C), the ability to resist deformation based on the high Young’s modulus of ∼775 MPa, and chemical resistance based on the swelling index and gel content. We envision the disclosed biobased resin having tailorable properties suitable for industrial applications.