Fluorescence Labeling of Technical Lignin for the Study of Phenolic Group Distribution as a Function of the Molecular Weight

A novel analytical approach based on fluorescence labeling was developed in the effort to increase the understanding of phenolic group distribution in technical lignins. Selective derivatization with a fluorophore (dansyl chloride) of lignin phenolic functionalities was quantitatively achieved under mild reaction conditions. Reference acetylated lignin and labeled lignin were analyzed by gel permeation chromatography (GPC) coupled to a UV–vis detector (set at 280 nm) and a fluorescence detector (λ excitation: 390 nm, λ emission: 550 nm) to discern the dansyl-linked phenol response from the lignin aromatic skeleton input. After data elaboration, valuable information about the phenolic group distribution as a function of molecular weight for different technical lignins was gathered. This novel analytical approach is applied to model lignin polymer thermal protection properties, a useful parameter in lignin valorization strategies

Oxidation of Isoeugenol by Salen Complexes with Bulky Substituents

The catalytic properties of bulky water-soluble salen complexes in the oxidation of isoeugenol (2-methoxy-4-(1-propenyl) phenol) have been investigated in aqueous ethanol solutions in order to obtain a mixture of polymeric compounds through dehydrogenative polymerization. The average molecular weight of dehydrogenated polymers (DHPs) was monitored by GPC and correlated to reaction conditions such as time, concentration of substrate, concentration of catalyst, type of oxidation agent, etc. The DHP synthesized by adopting the best reaction conditions was characterized by different analytical techniques (GPC, 13C-NMR, 31P-NMR and LC-MS) to elucidate its structure. The lignin-like polymer resulting from isoeugenol radical coupling possesses valuable biological activity and finds applications in a variety of fields, such as packaging industry and cultural heritage conservation

Oxidation of Isoeugenol by Salen Complexes with Bulky Substituents

The catalytic properties of bulky water-soluble salen complexes in the oxidation of isoeugenol(2-methoxy-4-(1-propenyl) phenol) have been investigated in aqueous ethanol solutions in order to obtain a mixture of polymeric compounds through dehydrogenative polymerization. The average molecular weight of dehydrogenated polymers (DHPs) was monitored by GPC and correlated to reaction conditions such as time, concentration of substrate, concentration of catalyst, type of oxidation agent, etc. The DHP synthesized by adopting the best reaction conditions was characterized by different analytical techniques (GPC, 13C-NMR, 31P-NMR and LC-MS) to elucidate its structure. The lignin-like polymer resulting from isoeugenol radical coupling possesses valuable biological activity and finds applications in a variety of fields, such as packaging industry and cultural heritage conservation

Epoxidized Lignin Derivatives as Bio-based Cross-linkers Used in the Preparation of Epoxy Resins

Lignin, which is the most abundant aromatic polymer in nature, was used as a green substitute for the toxic bisphenol A. In particular, the ability of epoxidized lignin to simultaneously serve as a cross-linker and rigid segment was investigated. The epoxidized lignin was preferably reacted with a monofunctional amine, which acted as a chain extender, to evaluate its performance as a cross-linker, and in the presence of poly(ethylene glycol) diglycidyl ether as a soft segment to adjust the resin properties. Different poly(ethylene glycol) diglycidyl ether/lignin stoichiometric ratios were tested, whereas the amine/epoxy equivalent ratio was fixed at 1:2. Some of the remarkable resin samples were subjected to differential scanning calorimetry analysis and compared with blank samples that did not include lignin in the composition. Moreover, the evolution over time of the molecular weight distribution of the selected compositions was analyzed by gel permeation chromatography until the solubility in tetrahydrofuran was appreciable

Epoxidized Lignin Derivatives as Bio-based Cross-linkers Used in the Preparation of Epoxy Resins

Lignin, which is the most abundant aromatic polymer in nature, was used as a green substitute for the toxic bisphenol A. In particular, the ability of epoxidized lignin to simultaneously serve as a cross-linker and rigid segment was investigated. The epoxidized lignin was preferably reacted with a monofunctional amine, which acted as a chain extender, to evaluate its performance as a cross-linker, and in the presence of poly(ethylene glycol) diglycidyl ether as a soft segment to adjust the resin properties. Different poly(ethylene glycol) diglycidyl ether/lignin stoichiometric ratios were tested, whereas the amine/epoxy equivalent ratio was fixed at 1:2. Some of the remarkable resin samples were subjected to differential scanning calorimetry analysis and compared with blank samples that did not include lignin in the composition. Moreover, the evolution over time of the molecular weight distribution of the selected compositions was analyzed by gel permeation chromatography until the solubility in tetrahydrofuran was appreciable

Exploring Allylation and Claisen Rearrangement as a Novel Chemical Modification of Lignin

The conversion of lignin into value-added products is traditionally hampered by its stochastic structure and its complex reactivity. The allylation reaction and the aromatic Claisen rearrangement of the allyl group on lignin as chemical modifications are reported for the first time in this work. This approach is aimed at the development of new lignin-based materials and the improvement of its compatibility and ease of processing. In particular, the Claisen rearrangement of lignin is foreseen as a valuable approach to release phenolic groups in an already chemically modified lignin, giving additional reactive sites for further transformation. These reactions were carried out on a purely guaiacylic lignin (TMP), taken as reference material due to its simplicity, and on a more structurally complex herbaceous lignin (P1000®). The Claisen rearrangement of the allylic chain was successfully achieved by treatment in dimethylformamide at reflux temperature for 15 hours. Finally, a screening of the antioxidant activity of reference, allylated, and Claisen rearranged lignins was carried out. Rearranged lignins exhibited satisfactory antioxidant activities if compared to the reference ones

Utilization of cyclocarbonated lignin as a bio-based cross-linker for the preparation of poly(hydroxy urethane)s

Preparation of thermoset poly(hydroxy urethane) exploiting cyclocarbonated lignin as cross-linker

Sphingoid esters from the molecular distillation of squid oil: A preliminary bioactivity determination

A mixture of sphingoid esters was isolated (1.4% w/w) from the molecular distillation of crude squid visceral oil. A preliminary investigation on the bioactivity profile and toxic potential of this residue was carried out by in vitro experiments. No cytotoxicity and a moderate lipase inhibition activity were highlighted

Valorization of Side-Streams from a SSF Biorefinery Plant: Wheat Straw Lignin Purification Study

The lignocellulosic materials produced after each step of a biorefinery plant using simultaneous saccharification and fermentation (SSF) technology on wheat straw (Triticum spp.) for bioethanol production were characterized by spectroscopic and chromatographic techniques in order to investigate the macromolecular interactions between the lignin and polysaccharides. In order to valorize the lignin cakes, a purification step was set up and the extraction conditions (acid pretreatment, temperature, time, and NaOH concentration) were optimized by a chemiometric approach in terms of yield and purity. Residual carbohydrate impurities, free and/or chemically bonded to lignin (lignin carbohydrates complexes), were individuate as the most critical factor for a satisfactory lignin extraction. Finally, the lignin samples collected according to the optimized extraction conditions were chemically characterized and low molecular weight, high phenols concentration, and low carboxylic acids content were recognized as interesting features for industrial applications