Browsing by Author "Koso, Tetyana V."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Assembling Native Elementary Cellulose Nanofibrils via a Reversible and Regioselective Surface Functionalization(AMERICAN CHEMICAL SOCIETY, 2021-10-20) Beaumont, Marco; Tardy, Blaise L.; Reyes, Guillermo; Koso, Tetyana V.; Schaubmayr, Elisabeth; Jusner, Paul; King, Alistair W.T.; Dagastine, Raymond R.; Potthast, Antje; Rojas, Orlando J.; Rosenau, Thomas; Department of Bioproducts and Biosystems; Bio-based Colloids and Materials; University of Helsinki; University of Natural Resources and Life Sciences, Vienna; University of MelbourneSelective surface modification of biobased fibers affords effective individualization and functionalization into nanomaterials, as exemplified by the TEMPO-mediated oxidation. However, such a route leads to changes of the native surface chemistry, affecting interparticle interactions and limiting the development of potential supermaterials. Here we introduce a methodology to extract elementary cellulose fibrils by treatment of biomass with N-succinylimidazole, achieving regioselective surface modification of C6-OH, which can be reverted using mild post-treatments. No polymer degradation, cross-linking, nor changes in crystallinity occur under the mild processing conditions, yielding cellulose nanofibrils bearing carboxyl moieties, which can be removed by saponification. The latter offers a significant opportunity in the reconstitution of the chemical and structural interfaces associated with the native states. Consequently, 3D structuring of native elementary cellulose nanofibrils is made possible with the same supramolecular features as the biosynthesized fibers, which is required to unlock the full potential of cellulose as a sustainable building block.Item Cellulose dissolution and gelation in NaOH(aq) under controlled CO2 atmosphere: supramolecular structure and flow properties(Royal Society of Chemistry, 2022-10-21) Reyes, Guillermo; King, Alistair W.T.; Koso, Tetyana V.; Penttilä, Paavo A.; Kosonen, Harri; Rojas, Orlando J.; Department of Bioproducts and Biosystems; Bio-based Colloids and Materials; Wood Material Science; VTT Technical Research Centre of Finland; University of Helsinki; UPM Research CenterWe investigate the interplay between cellulose crystallization and aggregation with interfibrillar interactions, shear forces, and the local changes in the medium's acidity. The latter is affected by the CO2 chemisorbed from the surrounding atmosphere, which, combined with shear forces, explain cellulose gelation. Herein, rheology, nuclear magnetic resonance (NMR), small and wide-angle X-ray scattering (SAXS/WAXS), and focused ion beam scanning electron microscopy (FIB-SEM) are combined to unveil the fundamental factors that limit cellulose gelation and maximize its dissolution in NaOH(aq). The obtained solutions are then proposed for developing green and environmentally friendly cellulose-based materials.Item Regioselective and water-assisted surface esterification of never-dried cellulose: nanofibers with adjustable surface energy(ROYAL SOC CHEMISTRY, 2021-09-21) Beaumont, Marco; Otoni, Caio G.; Mattos, Bruno D.; Koso, Tetyana V.; Abidnejad, Roozbeh; Zhao, Bin; Kondor, Anett; King, Alistair W. T.; Rojas, Orlando J.; Department of Bioproducts and Biosystems; Bio-based Colloids and Materials; Universidade Federal de São Carlos; University of Helsinki; Surface Measurement Systems LtdA new regioselective route is introduced for surface modification of biological colloids in the presence of water. Taking the case of cellulose nanofibers (CNFs), we demonstrate a site-specific (93% selective) reaction between the primary surface hydroxyl groups (C6-OH) of cellulose and acyl imidazoles. CNFs bearing C6-acetyl and C6-isobutyryl groups, with a degree of substitution of up to 1 mmol g(-1) are obtained upon surface esterification, affording CNFs of adjustable surface energy. The morphological and structural features of the nanofibers remain largely unaffected, but the regioselective surface reactions enable tailoring of their interfacial interactions, as demonstrated in oil/water Pickering emulsions. Our method precludes the need for drying or exchange with organic solvents for surface esterification, otherwise needed in the synthesis of esterified colloids and polysaccharides. Moreover, the method is well suited for application at high-solid content, opening the possibility for implementation in reactive extrusion and compounding. The proposed acylation is introduced as a sustainable approach that benefits from the presence of water and affords a high chemical substitution selectivity.