Despite the structural, load-bearing role of cellulose in the plant kingdom, countless efforts have been devoted to degrading this recalcitrant polysaccharide, particularly in the context of biofuels and renewable nanomaterials. Herein, we show how the exposure of plant-based fibers to HCl vapor results in rapid degradation with simultaneous crystallization. Because of the unchanged sample texture and the lack of mass transfer out of the substrate in the gas/solid system, the changes in the crystallinity could be reliably monitored. Furthermore, we describe the preparation of cellulose nanocrystals in high yields and with minimal water consumption. The study serves as a starting point for the solid-state tuning of the supramolecular properties of morphologically heterogeneous biological materials.

Swelling behavior and rearrangements of an amorphous ultrathin cellulose film (20 nm thickness) exposed to water and subsequently dried were investigated with grazing incidence X-ray diffraction, neutron reflectivity, atomic force microscopy, and surface energy calculations obtained from contact angle measurements. The film swelled excessively in water, doubling its thickness, but shrunk back to the original thickness upon water removal. Crystallinity (or amorphousness) and morphology remained relatively unchanged after the wetting/drying cycle, but surface free energy increased considerably (ca. 15%) due to an increase in its polar component, that is, the hydrophilicity of the film, indicating that rearrangements occurred during the film's exposure to water. Furthermore, stability of the films in aqueous NaOH solution was investigated with quartz crystal microbalance with dissipation monitoring. The films were stable at 0.0001 M NaOH but already 0.001 M NaOH partially dissolved the film. The surprising susceptibility to dissolve in dilute NaOH was hypothetically attributed to the lack of hierarchical morphology in the amorphous film.

Small-angle scattering methods allow an efficient characterization of the hierarchical structure of wood and other cellulosic materials. However, their full utilization would require an analytical model to fit the experimental data. This contribution presents a small-angle scattering model tailored to the analysis of wood samples. The model is based on infinitely long cylinders packed in a hexagonal array with paracrystalline distortion, adapted to the particular purpose of modelling the packing of cellulose microfibrils in the secondary cell wall of wood. The new model has been validated with small-angle neutron and X-ray scattering data from real wood samples at various moisture contents. The model yields reasonable numerical values for the microfibril diameter (2.1–2.5 nm) and packing distance (4 and 3 nm in wet and dry states, respectively) and comparable results between the two methods. It is particularly applicable to wet wood samples and allows changes in the packing of cellulose microfibrils to be followed as a function of moisture content.

The production of lignin nanoparticles (LNPs) has opened new routes to 18 utilization of lignin in advanced applications. The existing challenge, however, is to 19 develop a production method that can easily be adapted on an industrial scale. In this 20 study, we demonstrated a green and rapid method of preparing LNPs directly from a 21 sulfur-free alkaline pulping liquor by combining acid-precipitation and ultrasonication. The 22 combined method produced spherical LNPs, with hierarchical nanostructure and highly 23 negative surface charge, within only 5-min of sonication. The mild, rapid sonication was 24 achieved by sonicating directly without prior drying the acid-precipitated and dialyzed 25 lignin. Optimization of the method revealed the potential for minimizing acid consumption, 26 shortening the dialysis time, and processing directly the alkaline liquor with as much as Page 2 of 54 ACS Paragon Plus Environment ACS Sustainable Chemistry & Engineering 3 27 20 wt% lignin. The isolated LNPs were stable during storage for 180 days, at a pH range 28 of 4-7 and in a dispersing medium below 0.1 M NaCl. The LNPs also displayed excellent 29 emulsifying properties, stabilizing oil-in-water emulsions. Thus, this simple and energyefficient method opens a sustainable, straightforward and scalable route to production of 31 solvent-free LNPs, with high potential as interface stabilizers of multi-phase systems in 32 the food and medical industries. 33 34 INTRODUCTION 35 Lignin, with its highly irregular polyphenolic structure, is the most abundant natural 36 aromatic polymer on Earth. 1 Representing 15-40% of the dry weight of lignocellulosics, 2 37 lignin is one of the major by-products in the pulp and paper industries, with an estimated 38 global production of 50 million tons per year. 3,4 Lignin production is expected to 39 continuously increase as the demand for second-generation biofuel, i.e. biofuels from 40 nonfood sources, is realized. In the USA alone, the mandate to produce 79 billion liters 41 of second-generation biofuels by 2022 translates into the production of 62 million tons of

No abstract

No abstract

To understand the limitations occurring during enzymatic hydrolysis of cellulosic materials in renewable energy production, we used wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), X-ray microtomography, and transmission electron microscopy (TEM) to characterize submicrometer changes in the structure of microcrystalline cellulose (Avicel) digested with the Trichoderma reesei enzyme system. The microtomography measurements showed a clear decrease in particle size in scale of tens of micrometers. In all the TEM pictures, similar elongated and partly ramified structures were observed, independent of the hydrolysis time. The SAXS results of rewetted samples suggested a slight change in the structure in scale of 10-20 nm, whereas the WAXS results confirmed that the degree of crystallinity and the crystal sizes remained unchanged. This indicates that the enzymes act on the surface of cellulose bundles and are unable to penetrate into the nanopores of wet cellulose.

No abstract