Literature is strongly contradictory about the molecular reasons for yellowing and brightness reversion of pure (lignin- and hemicellulose-free) celluloses, such as in highly bleached pulps, bacterial cellulose, or cotton linters. While oxidized groups—carbonyls (CO) and carboxyls (COOH)—have been recognized as the initiators of yellowing, they are generally always found together; thus, their effects are permanently superimposed in real-world cellulose. For this reason, their individual contributions could not be reliably determined. To tackle this conundrum, we have used a two-stage study: the employment of glucopyranose-derived model compounds and the use of special cellulosic pulps. Both substrates had either only carbonyl functions, only carboxyl functions, or defined ratios of both functionalities present at the same time. The model compounds alone already provided strong indications of the CO-related and COOH-related effects, and further confirmation was obtained by the pulp study. Here, in regard to the polymer case, the carbonyl groups are the minimum functional unit in cellulose responsible for chromophore generation (termed as the “CO effect”). The carbonyl groups are the precursors for the chromophores that are formed later upon yellowing/aging. Chromophore formation increases strictly linearly with the carbonyl content at a constant given carboxyl content. Carboxyl groups alone (i.e., in the absence of carbonyl groups) are fully innocent regarding the color generation. However, they have a strong promotive action when carbonyl groups are present (termed as the “COOH effect”), which includes acidic catalysis and an additional activation by electronic effects. The general roles of CO and COOH are the same for all aging types (e.g., thermal, acidic, or alkaline), while the respective rates of chromophore generation evidently depend on various parameters such as the temperature, medium, and pH value.

The compatibility of three different types of lignin, such as Kraft lignin, Organosolv lignin, and lignosulfonate, with PLA, in particular without the addition of any further reagents or compatibilizers, is investigated. The unmodified lignins were thoroughly characterized to establish their interaction potential in lignin-PLA composite formation. The obtained double-extruded binary systems containing 5, 10, and 15 wt % lignin in PLA were characterized in terms of chemical conversion (³¹P NMR), thermal behavior (TGA, DSC), and cellular morphology (SEM). Additionally, the flexural and impact properties as well as the melt volume rate (MVR) of the extruded materials, in the form of 3D-printed bars, were analyzed, and the effect of lignin addition to PLA studied. The results revealed poor mechanical properties for the Kraft lignin-PLA blends, but higher compatibility of Organosolv lignin-PLA blends. Lignosulfonate-PLA blends showed a promising behavior for 3D-printing. A special nucleation effect, potentially useful in foaming applications, was observed in this study.

Polysaccharides, oligosaccharides, and their derivatives, particularly of amylose, cellulose, chitosan, and β-cyclodextrin, are well-known chiral selectors (CSs) of chiral stationary phases (CSPs) in chromatography, because they can separate a wide range of enantiomers. Typically, such CSPs are prepared by physically coating, or chemically immobilizing the polysaccharide and β-cyclodextrin derivatives onto inert silica gel carriers as chromatographic support. Over the past few years, new chiral selectors have been introduced, and progressive methods to prepare CSPs have been exploited. Also, chiral recognition mechanisms, which play a crucial role in the investigation of chiral separations, have been better elucidated. Further insights into the broad functional performance of commercially available chiral column materials and/or the respective newly developed chiral phase materials on enantiomeric separation (ES) have been gained. This review summarizes the recent developments in CSs, CSP preparation, chiral recognition mechanisms, and enantiomeric separation methods, based on polysaccharides and β-cyclodextrins as CSs, with a focus on the years 2019–2020 of this rapidly developing field.

A method based on headspace-isotope dilution (HS-ID) GC-MS for the quantitative analysis of methoxyl and ethoxyl groups in any kind of lignin has been developed. The method involves the application of an isotopically labeled internal standard (4-(methoxy-d₃)-benzoic acid and 4-(ethoxy-d₅)-benzoic acid), which, together with lignin, undergoes standard hydroiodic acid cleavage of methoxyl and ethoxyl groups, followed by headspace GC-MS analysis of the respective deuterated and non-deuterated iodomethanes and iodoethanes. As also the internal standard is generated in situ during ether cleavage, any variations in the procedure are levelled out. The application of the isotopically labeled internal standard essentially increased the robustness of the overall approach. The accuracy and precision of methoxyl and ethoxyl group quantification in lignins have been assessed, and the data were compared to the classical Zeisel–Vieböck–Schwappach method for methoxyl groups in lignins. The novel approach for methoxyl and ethoxyl group determination showed a more satisfactory precision, accuracy, and also a much higher sample throughput, with approximately 40 samples per day.