Here we present a general concept of wet surface esterification of cellulose using acyl imidazoles, which enables direct acetylation of never-dried cellulose fibres in aqueous conditions. We hope that due...

The mechanical reinforcement of porous materials made of microfibrillated cellulose by in situ polymerisation of furfuryl alcohol prior to freezedrying from aqueous slurry was studied. Besides a slight improvement in the modulus of elasticity measured in compression testing, no beneficial effects of furfuryl alcohol addition on porous materials produced from microfibrillated cellulose derived from bleached softwood pulp were observed. By contrast, when microfibrillated cellulose containing substantial amounts of residual non-cellulosic cell wall polymers, termed microfibrillated lignocellulose, was used, clear mechanical reinforcement effects due to furfuryl alcohol addition were measured. By means of SEM, significantly improved wetting of the cellulosic fibrillary architecture of porous materials with furfuryl alcohol was observed for microfibrillated lignocellulose compared to microfibrillated cellulose. It is proposed that the specific surface-chemical character of microfibrillated lignocellulose enables wetting of fibrils with furfuryl alcohol, thus providing micron fibre-reinforced structures with improved strength after in situ polymerisation. Besides mechanical properties, the density and thermal stability of cellulose-based porous materials were found to increase with increasing amounts of furfuryl alcohol added to the initial reaction slurry.

Homogeneous solutions of Kraft lignin can be prepared in alkali. In this environment, ozonean effective and established bleaching agentrapidly converts into a variety of reactive oxygen species, leading to complex oxidation processes. In this study, Kraft lignin was treated with ozone in alkaline solution, and the modified lignin was fractionated into a precipitable, an adsorbable, and a soluble fraction to trace and understand the effects of this treatment. Changing the starting pH showed a distinct effect on the proportion of the obtained fractions. During the oxidation process, several small organic compounds were formed, resulting in a severe drop in pH and a shift in the predominant reactive species. In addition, these fragments were linked quantitatively to specific reaction pathways, which allowed the study of occurring degradation mechanisms. Here, a clear predominance of ring-opening reactions over side chain cleavage was observed. Chemical characterization revealed an increase in carboxyl and a decrease in methoxyl groups in the lignin polymer, thus increasing its solubility at neutral pH.