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Cellulose ferulate, synthesized by Mitsunobu reaction, is shaped into thin films and also used as an aqueous dispersion to perform artificial lignin polymerization on anchor groups. This biomimetic approach is carried out in a Quartz crystal microbalance with a dissipation monitoring (QCM-D) device to enable online monitoring of the dehydrogenation, applying H 2 O 2 and adsorbed horseradish peroxidase (HRP). The systematic use of phenylpropanoids with different oxidation states, i.e., ferulic acid, coniferyl aldehyde, coniferyl alcohol, and eugenol allowed to conclude structure-property relationships. Both the deposited material, as well as the surface roughness increased with the hydrophobicity of the monomers. Beyond surface characterizations, py-GC-MS, HSQC NMR spectroscopy and Size exclusion chromatography (SEC) measurements revealed the linkage types β-β, β-5, 5-5, and β-O-4, as well as the oligomeric character of the dehydrogenation products. All samples possessed an antibacterial activity against B. subtilis and can be used in the field of antimicrobial biomaterials., (© 2024 The Authors. Macromolecular Bioscience published by Wiley‐VCH GmbH.)

Thin films of cellulose ferulate were designed to study the formation of dehydrogenation polymers (DHPs) on anchor groups of the surface. Trimethylsilyl (TMS) cellulose ferulate with degree of substitution values of 0.35 (ferulate) and 2.53 (TMS) was synthesized by sophisticated polysaccharide chemistry applying the Mitsunobu reaction. The biopolymer derivative was spin-coated into thin films to yield ferulate moieties on a smooth cellulose surface. Dehydrogenative polymerization of coniferyl alcohol was performed in a Quartz crystal microbalance with a dissipation monitoring device in the presence of H 2 O 2 and adsorbed horseradish peroxidase. The amount of DHP formed on the surface was found to be independent of the base layer thickness from 14 to 75 nm. Pyrolysis-GC-MS measurements of the DHP revealed β-O-4 and β-5 linkages. Mimicking lignification of plant cell walls on highly defined model films enables reproducible investigations of structure-property relationships.

In this issue, different chemical (alkaline and sulfite pulping, ozonolysis) and mechanical (vibratory ball milling) pre-treatments were utilized for activating wheat straw and beech sawdust prior to carboxymethylation. Detailed analysis by a range of methods, including Klason-lignin, cellulose and hemicellulose quantification, Powder-X-ray diffraction (PXRD) and attenuated total reflection (ATR) IR spectroscopy, enabled the investigation of material alterations. Subsequently, carboxymethylation was carried out with both untreated and activated materials, allowing the evaluation of activation steps by determining degrees of substitution with carboxymethyl groups (DS CM ). Moreover, carboxymethylation conditions were optimized, realizing high DS CM of up to 1.05. Results further revealed that ball milling enhanced the subsequent conversion; whereas chemical pre-treatments did not effectively increase material accessibilities. Further studies on chemically untreated materials emphasized that a highly reactive surface was already generated in the course of the carboxymethylation, inter alia through the concomitant dissolution of matrix components., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Micro-spectral analysis and fluorescence decay experiments of beech and oak chips as well as their main constituents lignin and cellulose are reported. While the lignin spectrum shows two fluorescence bands of almost identical intensity around 500 nm and 560 nm, the cellulose spectrum is dominated by a band around 500 with a less pronounced shoulder at 560 nm, whose intensity increases with the amount of residual lignin. Fluorescence decay kinetics are bi-exponential with lifetimes around 0.5 ns and 2.5 ns and an increasing contribution of the short-lived component with an increasing amount of lignin. Both data sets indicate that a quantification of residual lignin in cellulose samples obtained after decomposition of beech wood appears possible in a concentration range of 2–10 %. This may provide a non-destructive and label-free test of the quality of decomposition. [ABSTRACT FROM AUTHOR]

The enzymatic conversion of lignins, possibly in combination with electrochemical oxidation, makes aromatics such as syringol, guaiacol, vanillin and catechol available in the qualities required by the fragrance industry. The lignins were obtained by soda digestion from wheat straw and Miscanthus, characterized and then converted with laccases. The overall yield amounted up to 9 wt % with a product spectrum confined to four substances. Catechol was the major product, with a fraction of ≈75 %. It can easily be isolated by extraction with acetone. [ABSTRACT FROM AUTHOR]

Lignin can be converted into monomeric products with the aid of molten salt media. Molten zinc chloride (ZnCl2)/potassium chloride (KCl) mixtures are suitable for this purpose. The application of an eutectic mixture with low melting points leads to similar main products as are obtained by pyrolysis. The hydrogenolysis of an organosolv lignin in molten salts of ZnCl2/KCl was investigated as a function of reaction temperature, residence time, and lignin concentration, and the composition of liquid products and monophenols was analyzed by gas chromatography-mass spectrometry (GC-MS). The yields can be optimized by the proper selection of the reaction temperature. A longer residence time and higher lignin concentrations lead to increased formation of solid residues and gaseous products. The liquid products mainly consist of substituted phenols derived from lignins. Polymeric products are the result of condensation reactions (i.e., the formation of new C-C linkages in the course of secondary reactions). [ABSTRACT FROM AUTHOR]

Thermotropic liquid crystalline polyesters with varied chemical structure are synthesized by melt transesterification polycondensation. They are employed as matrix for blends with lignin materials to obtain melt‐spinnable precursors for carbon fibers. The lignin samples are carefully purified by fractionation, enzymatic removal of reducing sugars, and subsequent modification of the terminal OH groups. Effective melt blending is achieved with liquid‐crystalline aromatic–aliphatic polyesters having melting ranges that match the softening temperature of the lignin fractions, which is necessary to prevent thermal decomposition of the lignin. Polyester/lignin blends are partially compatibilized, phase‐separated materials. The polyester/lignin materials are melt‐spun successfully. The fiber properties depend on the lignin purification process. X‐ray scattering reveals that orientation in lignin‐containing fibers is maintained. First experiments show that the fibers can be converted successfully to carbon fibers by thermal annealing procedures. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48257. [ABSTRACT FROM AUTHOR]

Lignin, a component of the cell walls of plants and the second most abundant biopolymer has long been regarded as disturbing substance in pulp production by paper industry. This view has changed in recent decades. Thus, lignin is increasingly regarded as an alternative to crude oil. Tuned and modified lignins have suitable properties to use them as building blocks for various applications as well as for the production of basic chemicals. By modifying lignin, its reactivity and uniformity can be increased. In addition, properties of the lignin can be changed and influenced by selective modification. By a solvent-free modification with dihydroxybenzene, aliphatic OH groups of the lignin side chain can be removed and covalent C C bonds to the aromatics can be formed. At the same time, aryl-alkyl ether cleavage occurs, which reduces the molecular weight of lignin by about one third. In addition, ongoing reactions result in the reduction in the molecular weight distribution. All this leads to a more uniform and reactive lignin which is interesting as a precursor for various applications. This work provides a deeper understanding of ongoing reactions with dihydroxybenzenes and the structure of modified lignins. [ABSTRACT FROM AUTHOR]

The chemical composition of a number of naturally aged construction wood samples of spruce, fir and oak was investigated. The content of lignin, polysaccharide, and extractives was determined using wet chemical and chromatographic methods. Differences to non-aged wood samples were found particularly found on oak wood samples with regard to lignin and polysaccharide content as well as to cellulose crystallinity. The composition of wood extractives of aged and non-aged wood samples revealed degradation processes due to oxidation and slight hydrolysis. The investigation showed that the relative content of the structural wood constituents depends on the sample age as well as the conditions they were aged under. The different degradation rates of those structural components may lead to contradictory results regarding their contents at certain degrees of aging. Cellulose crystallinity values are affected by extractives content. [ABSTRACT FROM AUTHOR]

Wheat straw, as one of the most abundant agricultural residues in Europe, was subjected to alkaline pulping, microwave-assisted alkaline pulping and organosolv pulping using formic acid and hydrogen peroxide. The obtained lignins were characterised by means of Klason–lignin, FT-IR spectroscopy, elementary analysis, thioacidolysis, SEC and different wet chemical methods. The emphasis here was on their structural differences, especially the content of functional groups like total hydroxyl, phenolic hydroxyl, carboxyl, carbonyl and methoxyl groups. In addition, numerous agricultural residues, for example barley straw, maize straw, sunflower stalks and horse manure, were characterised and subjected to alkaline pulping, which was carried out based on the optimum parameters found for wheat straw: θ = 160 °C, t = 30 min and ω (NaOH) = 3 wt%. The examined raw materials showed different suitability for lignin separation using this pretreatment. The resulting lignins were characterised with the methods described above and were classified into three groups within which lignins show similar characteristics. By this, lignin with interesting structural features could be proposed for further studies. [ABSTRACT FROM AUTHOR]