Browsing by Author "King, Alistair W.T."

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  • 2D Assignment and quantitative analysis of cellulose and oxidized celluloses using solution-state NMR spectroscopy
    (2020-09-01) Koso, Tetyana; Rico del Cerro, Daniel; Heikkinen, Sami; Nypelö, Tiina; Buffiere, Jean; Perea-Buceta, Jesus E.; Potthast, Antje; Rosenau, Thomas; Heikkinen, Harri; Maaheimo, Hannu; Isogai, Akira; Kilpeläinen, Ilkka; King, Alistair W.T.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The limited access to fast and facile general analytical methods for cellulosic and/or biocomposite materials currently stands as one of the main barriers for the progress of these disciplines. To that end, a diverse set of narrow analytical techniques are typically employed that often are time-consuming, costly, and/or not necessarily available on a daily basis for practitioners. Herein, we rigorously demonstrate a general quantitative NMR spectroscopic method for structural determination of crystalline cellulose samples. Our method relies on the use of a readily accessible ionic liquid electrolyte, tetrabutylphosphonium acetate ([P-4444][OAc]):DMSO-d(6), for the direct dissolution of biopolymeric samples. We utilize a series of model compounds and apply now classical (nitroxyl-radical and periodate) oxidation reactions to cellulose samples, to allow for accurate resonance assignment, using 2D NMR. Quantitative heteronuclear single quantum correlation (HSQC) was applied in the analysis of key samples to assess its applicability as a high-resolution technique for following cellulose surface modification. Quantitation using HSQC was possible, but only after applying T(2)correction to integral values. The comprehensive signal assignment of the diverse set of cellulosic species in this study constitutes a blueprint for the direct quantitative structural elucidation of crystalline lignocellulosic, in general, readily available solution-state NMR spectroscopy. [GRAPHICS] .
  • Assembling Native Elementary Cellulose Nanofibrils via a Reversible and Regioselective Surface Functionalization
    (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
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Selective 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.
  • Binary mixtures of ionic liquids-DMSO as solvents for the dissolution and derivatization of cellulose: Effects of alkyl and alkoxy side chains
    (2019-05-15) Ferreira, Daniela C.; Oliveira, Mayara L.; Bioni, Thais A.; Nawaz, Haq; King, Alistair W.T.; Kilpeläinen, Ilkka; Hummel, Michael; Sixta, Herbert; El Seoud, Omar A.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The efficiency of mixtures of ionic liquids (ILs) and molecular solvents in cellulose dissolution and derivatization depends on the structures of both components. We investigated the ILs 1-(1-butyl)-3-methylimidazolium acetate (C 4 MeImAc) and 1-(2-methoxyethyl)-3-methylimidazolium acetate (C 3 OMeImAc) and their solutions in dimethyl sulfoxide, DMSO, to assess the effect of presence of an ether linkage in the IL side-chain. Surprisingly, C 4 MeImAc-DMSO was more efficient than C 3 OMeImAc-DMSO for the dissolution and acylation of cellulose. We investigated both solvents using rheology, NMR spectroscopy, and solvatochromism. Mixtures of C 3 OMeImAc-DMSO are more viscous, less basic, and form weaker hydrogen bonds with cellobiose than C 4 MeImAc-DMSO. We attribute the lower efficiency of C 3 OMeImAc to “deactivation” of the ether oxygen and C2–H of the imidazolium ring due to intramolecular hydrogen bonding. Using the corresponding ILs with C2–CH 3 instead of C2–H, namely, 1-butyl-2,3-dimethylimidazolium acetate (C 4 Me 2 ImAc) and 1-(2-methoxyethyl)-2,3-dimethylimidazolium acetate (C 3 OMe 2 ImAc) increased the concentration of dissolved cellulose; without noticeable effect on biopolymer reactivity.
  • Bioactive Fiber Foam Films from Cellulose and Willow Bark Extract with Improved Water Tolerance
    (2024-02-20) Lohtander, Tia; Koso, Tetyana; Huynh, Ngoc; Hjelt, Tuomo; Gestranius, Marie; King, Alistair W.T.; Österberg, Monika; Arola, Suvi
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Cellulose-based materials are gaining increasing attention in the packaging industry as sustainable packaging material alternatives. Lignocellulosic polymers with high quantities of surface hydroxyls are inherently hydrophilic and hygroscopic, making them moisture-sensitive, which has been retarding the utilization of cellulosic materials in applications requiring high moisture resistance. Herein, we produced lightweight all-cellulose fiber foam films with improved water tolerance. The fiber foams were modified with willow bark extract (WBE) and alkyl ketene dimer (AKD). AKD improved the water stability, while the addition of WBE was found to improve the dry strength of the fiber foam films and bring additional functionalities, that is, antioxidant and ultraviolet protection properties, to the material. Additionally, WBE and AKD showed a synergistic effect in improving the hydrophobicity and water tolerance of the fiber foam films. Nuclear magnetic resonance (NMR) spectroscopy indicated that the interactions among WBE, cellulose, and AKD were physical, with no formation of covalent bonds. The findings of this study broaden the possibilities to utilize cellulose-based materials in high-value active packaging applications, for instance, for pharmaceutical and healthcare products or as water-resistant coatings for textiles, besides bulk packaging materials.
  • Cellulose dissolution and gelation in NaOH(aq) under controlled CO2 atmosphere: supramolecular structure and flow properties
    (2022-10-21) Reyes, Guillermo; King, Alistair W.T.; Koso, Tetyana V.; Penttilä, Paavo A.; Kosonen, Harri; Rojas, Orlando J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We 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.
  • Challenges in Synthesis and Analysis of Asymmetrically Grafted Cellulose Nanocrystals via Atom Transfer Radical Polymerization
    (2021-06-14) Delepierre, Gwendoline; Heise, Katja; Malinen, Kiia; Koso, Tetyana; Pitkänen, Leena; Cranston, Emily D.; Kilpeläinen, Ilkka; Kostiainen, Mauri A.; Kontturi, Eero; Weder, Christoph; Zoppe, Justin O.; King, Alistair W.T.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    When cellulose nanocrystals (CNCs) are isolated from cellulose microfibrils, the parallel arrangement of the cellulose chains in the crystalline domains is retained so that all reducing end-groups (REGs) point to one crystallite end. This permits the selective chemical modification of one end of the CNCs. In this study, two reaction pathways are compared to selectively attach atom-transfer radical polymerization (ATRP) initiators to the REGs of CNCs, using reductive amination. This modification further enabled the site-specific grafting of the anionic polyelectrolyte poly(sodium 4-styrenesulfonate) (PSS) from the CNCs. Different analytical methods, including colorimetry and solution-state NMR analysis, were combined to confirm the REG-modification with ATRP-initiators and PSS. The achieved grafting yield was low due to either a limited conversion of the CNC REGs or side reactions on the polymerization initiator during the reductive amination. The end-tethered CNCs were easy to redisperse in water after freeze-drying, and the shear birefringence of colloidal suspensions is maintained after this process.
  • Chemical Modification of Reducing End-Groups in Cellulose Nanocrystals
    (2021-01-04) Heise, Katja; Delepierre, Gwendoline; King, Alistair W.T.; Kostiainen, Mauri A.; Zoppe, Justin; Weder, Christoph; Kontturi, Eero
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    Native plant cellulose has an intrinsic supramolecular structure. Consequently, it can be isolated as nanocellulose species, which can be utilized as building blocks for renewable nanomaterials. The structure of cellulose also permits its end-wise modification, i.e., chemical reactions exclusively on one end of a cellulose chain or a nanocellulose particle. The premises for end-wise modification have been known for decades. Nevertheless, different approaches for the reactions have emerged only recently, because of formidable synthetic and analytical challenges associated with the issue, including the adverse reactivity of the cellulose reducing end and the low abundance of newly introduced functionalities. This Review gives a full account of the scientific underpinnings and challenges related to end-wise modification of cellulose nanocrystals. Furthermore, we present how the chemical modification of cellulose nanocrystal ends may be applied to directed assembly, resulting in numerous possibilities for the construction of new materials, such as responsive liquid crystal templates and composites with tailored interactions.
  • Combining Rigid Cellulose Nanocrystals and Soft Silk Proteins: Revealing Interactions and Alignment in Shear
    (2023-07-17) Leppänen, Ilona; Arola, Suvi; King, Alistair W.T.; Unger, Miriam; Stadler, Hartmut; Nissen, Gry Sofie; Zborowski, Charlotte; Virtanen, Tommi; Salmela, Juha; Setälä, Harri; Lésage, Stephanie; Österberg, Monika; Tammelin, Tekla
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Natural materials, such as silk and cellulose, have an inspiring set of properties, which have evolved over hundreds of millions of years. In this study, cellulose nanocrystals (CNCs) and regenerated silk fibroin (RSF) are combined to evaluate their suitability for filament formation. This is assessed by tuning and characterizing the interactions between these two materials and finally by studying the alignment of the mixtures under shear. To modify the interactions between CNCs and silk, CNCs with varying surface functionalities (sulfate and/or aminosilane groups) are used. The interactions and compatibility of the two components are investigated using quartz crystal microbalance with dissipation monitoring (QCM-D) and photothermal atomic force microscopy (AFM-IR), which show that ionic interactions induce sufficient binding between the two components. Then, the alignment of the CNC and silk mixtures is evaluated by shear-induced polarized light imaging, which indicates that silk can orientate with the CNCs when not covalently bound. Finally, the potential of the materials for filament formation is tentatively demonstrated using an industrial dry-spinning environment, where CNCs are expected to bring order and alignment, whereas RSF provides soft and more mobile regions to further facilitate the alignment of the final filament structure.
  • A comparative study of water-immiscible organic solvents in the production of furfural from xylose and birch hydrolysate
    (2019-04-25) Gómez Millán, Gerardo; Hellsten, Sanna; King, Alistair W.T.; Pokki, Juha-Pekka; Llorca, Jordi; Sixta, Herbert
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Furfural (FUR) was produced from xylose using a biphasic batch reaction system. Water-immiscible organic solvents such as isophorone, 2-methyltetrahydrofuran (2-MTHF) and cyclopentyl methyl ether (CPME) were used to promptly extract FUR from the aqueous phase in order to avoid the degradation to humins as largely as possible. The effect of time, temperature, organic solvent and organic-to-aqueous ratio on xylose conversion and FUR yield were investigated in auto-catalyzed conditions. Experiments at three temperatures (170, 190 and 210 °C) were carried out in a stirred microwave-assisted batch reactor, which established the optimal conditions for achieving the highest FUR yield. The maximum FUR yields from xylose were 78 mol% when using CPME, 48 mol% using isophorone and 71 mol% in the case of 2-MTHF at an aqueous to organic phase ratio of 1:1 (v/v). Birch hydrolysate was also used to show the high furfural yield that can be obtained in the biphasic system under optimized conditions. The present study suggests that CPME can be used as a green and efficient extraction solvent for the conversion of xylose into furfural without salt addition.
  • Enhanced activity of hyperthermostable Pyrococcus horikoshii endoglucanase in superbase ionic liquids
    (2022-08) Hebal, Hakim; Hämäläinen, Joonas; Makkonen, Laura; King, Alistair W.T.; Kilpeläinen, Ilkka; Bankar, Sandip; Boucherba, Nawel; Turunen, Ossi
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Objectives: Ionic liquids (ILs) that dissolve biomass are harmful to the enzymes that degrade lignocellulose. Enzyme hyperthermostability promotes a tolerance to ILs. Therefore, the limits of hyperthemophilic Pyrococcus horikoschii endoglucanase (PhEG) to tolerate 11 superbase ILs were explored.  Results: PhEG was found to be most tolerant to 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) in soluble 1% carboxymethylcellulose (CMC) and insoluble 1% Avicel substrates. At 35% concentration, this IL caused an increase in enzyme activity (up to 1.5-fold) with CMC. Several ILs were more enzyme inhibiting with insoluble Avicel than with soluble CMC. Km increased greatly in the presence ILs, indicating significant competitive inhibition. Increased hydrophobicity of the IL cation or anion was associated with the strongest enzyme inhibition and activation. Surprisingly, PhEG activity was increased 2.0–2.5-fold by several ILs in 4% substrate. Cations exerted the main role in competitive inhibition of the enzyme as revealed by their greater binding energy to the active site.  Conclusions: These results reveal new ways to design a beneficial combination of ILs and enzymes for the hydrolysis of lignocellulose, and the strong potential of PhEG in industrial, high substrate concentrations in aqueous IL solutions.
  • High-Performance Acetylated Ioncell-F Fibers with Low Degree of Substitution
    (2018-07-02) Asaadi, Shirin; Kakko, Tia; King, Alistair W.T.; Kilpeläinen, Ilkka; Hummel, Michael; Sixta, Herbert
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Cellulose acetate is one of the most important cellulose derivatives. Herein we present a method to access cellulose acetate with a low degree of substitution through a homogeneous reaction in the ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]). This ionic liquid has also been identified as an excellent cellulose solvent for dry-jet wet fiber spinning. Cellulose was dissolved in [DBNH][OAc] and esterified in situ to be immediately spun into modified cellulose filaments with a degree of substitution (DS) value of 0.05-0.75. The structural properties of the resulting fibers, which are characterized by particularly high tensile strength values (525-750 MPa conditioned and 315-615 MPa wet) and elastic moduli between 10-26 GPa, were investigated by birefringence measurements, wide-angle X-ray scattering, and molar mass distribution techniques while their unique interactions with water have been studied through dynamic vapor sorption. Thus, an understanding of the novel process is gained, and the advantages are demonstrated for producing high-value products such as textiles, biocomposites, filters, and membranes.
  • Highly regioselective surface acetylation of cellulose and shaped cellulose constructs in the gas-phase
    (2022-07-21) Koso, Tetyana; Beaumont, Marco; Tardy, Blaise L.; Rico del Cerro, Daniel; Eyley, Samuel; Thielemans, Wim; Rojas, Orlando J.; Kilpeläinen, Ilkka; King, Alistair W.T.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Gas-phase acylation is an attractive and sustainable method for modifying the surface properties of cellulosics. However, little is known concerning the regioselectivity of the chemistry, i.e., which cellulose hydroxyls are preferentially acylated and if acylation can be restricted to the surface, preserving crystallinities/morphologies. Consequently, we reexplore simple gas-phase acetylation of modern-day cellulosic building blocks - cellulose nanocrystals, pulps, dry-jet wet spun (regenerated cellulose) fibres and a nanocellulose-based aerogel. Using advanced analytics, we show that the gas-phase acetylation is highly regioselective for the C6-OH, a finding also supported by DFT-based transition-state modelling on a crystalloid surface. This contrasts with acid- and base-catalysed liquid-phase acetylation methods, highlighting that gas-phase chemistry is much more controllable, yet with similar kinetics, to the uncatalyzed liquid-phase reactions. Furthermore, this method preserves both the native (or regenerated) crystalline structure of the cellulose and the supramolecular morphology of even delicate cellulosic constructs (nanocellulose aerogel exhibiting chiral cholesteric liquid crystalline phases). Due to the soft nature of this chemistry and an ability to finely control the kinetics, yielding highly regioselective low degree of substitution products, we are convinced this method will facilitate the rapid adoption of precisely tailored and biodegradable cellulosic materials.
  • Immobilization of natural lipid biomembranes and their interactions with choline carboxylates. A nanoplasmonic sensing study
    (2020-02-01) Duša, Filip; Chen, Wen; Witos, Joanna; Rantamäki, Antti H.; King, Alistair W.T.; Sklavounos, Evangelos; Roth, Michal; Wiedmer, Susanne K.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The cell membrane is mainly composed of lipid bilayers with inserted proteins and carbohydrates. Lipid bilayers made of purified or synthetic lipids are widely used for estimating the effect of target compounds on cell membranes. However, the composition of such biomimetic membranes is much simpler than the composition of biological membranes. Interactions between compounds and simple composition biomimetic membranes might not demonstrate the effect of target compounds as precisely as membranes with compositions close to real organisms. Therefore, the aim of our study is to construct biomimetic membrane closely mimicking the state of natural membranes. Liposomes were prepared from lipids extracted from L-α-phosphatidylcholine, Escherichia coli, yeast (Saccharomyces cerevisiae) and bovine liver cells through agitation and sonication. They were immobilized onto silicon dioxide (SiO2) sensor surfaces using N-(2-hydroxyethyl)piperazine-N′-2-ethanesulfonic acid buffer with calcium chloride. The biomimetic membranes were successfully immobilized onto the SiO2 sensor surface and detected by nanoplasmonic sensing. The immobilized membranes were exposed to choline carboxylates. The membrane disruption effect was, as expected, more pronounced with increasing carbohydrate chain length of the carboxylates. The results correlated with the toxicity values determined using Vibrio fischeri bacteria. The yeast extracted lipid membranes had the strongest response to introduction of choline laurate while the bovine liver lipid extracted liposomes were the most sensitive towards the shorter choline carboxylates. This implies that the composition of the cell membrane plays a crucial role upon interaction with choline carboxylates, and underlines the necessity of testing membrane systems of different origin to obtain an overall image of such interactions.
  • Inhibition of hyperthermostable xylanases by superbase ionic liquids
    (2020-08) Hebal, Hakim; Parviainen, Arno; Anbarasan, Sasikala; Li, He; Makkonen, Laura; Bankar, Sandip; King, Alistair W.T.; Kilpeläinen, Ilkka; Benallaoua, Said; Turunen, Ossi
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The use of enzymes in aqueous solutions of ionic liquids (ILs) could be useful for the enzymatic treatment of lignocellulose. Hydrophilic ILs that dissolve lignocellulose are harmful to enzymes. The toleration limits and enzyme-friendly superbase IL combinations were investigated for the hyperthermophilic Thermopolyspora flexuosa GH10 xylanase (endo-1,4-β-xylanase EC 3.2.1.8) TfXYN10A and Dictyoglomus thermophilum GH11 xylanase DtXYN11B. TfXYN10A was more tolerant than DtXYN11B to acetate or propionate-based ILs. However, when the anion of the ILs was bigger (guaiacolate), GH11 xylanase showed higher tolerance to ILs. 1-Ethyl-3-methylimidazolium acetate ([EMIM]OAc), followed by 1,1,3,3-tetramethylguanidine acetate ([TMGH]OAc), were the most enzyme-friendly ILs for TfXYN10A and [TMGH]+-based ILs were tolerated best by DtXYN11B. Double-ring cations and a large size anion were associated with the strongest enzyme inhibition. Competitive inhibition appears to be a general factor in the reduction of enzyme activity. However, with guaiacolate ILs, the denaturation of proteins may also contribute to the reduction in enzyme activity. Molecular docking with IL cations and anions indicated that the binding mode and shape of the active site affect competitive inhibition, and the co-binding of cations and anions to separate active site positions caused the strongest enzyme inhibition.
  • LPMO-Catalyzed Oxidation of Cellulosic Fibers with Controlled Addition of a Reductant and H2O2
    (2025-01-13) Marjamaa, Kaisa; Rahikainen, Jenni; Støpamo, Fredrik G.; Sulaeva, Irina; Hosia, Waltteri; Maiorova, Natalia; King, Alistair W.T.; Potthast, Antje; Kruus, Kristiina; Eijsink, Vincent G.H.; Várnai, Anikó
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Cellulose-derived biomaterials offer a sustainable and versatile platform for various applications. Enzymatic engineering of these fibers, particularly using lytic polysaccharide monooxygenases (LPMOs), shows promise due to the ability to introduce functional groups onto cellulose surfaces, potentially enabling further functionalization. However, harnessing LPMOs for fiber engineering remains challenging, partly because controlling the enzymatic reaction is difficult and partly because limited information is available about how LPMOs modify the fibers. In this study, we explored controlling LPMO-mediated fiber oxidation by sequentially adding a reductant (gallic acid, GA) and H2O2, using three different carbohydrate-binding module (CBM)-containing LPMOs. An in-depth analysis of the soluble products and the Mn, Mw, and carbonyl content in the fiber fraction indicates that fiber oxidation can indeed be controlled by adjusting the amount of GA and H2O2 added to the reaction. In particular, at lower overall dosages of GA and H2O2, corresponding to low oxidation levels, fiber oxidation occurs rapidly with almost no release of soluble oxidized products. Conversely, at higher dosages, fiber oxidation levels off, while oxidized oligosaccharides continue to be released and the fibers are eroded. Importantly, next to demonstrating controlled fiber oxidation, this study shows that different cellulose-active LPMOs modify the fibers in different manners.
  • Plasticized Cellulosic Films by Partial Esterification and Welding in Low-Concentration Ionic Liquid Electrolyte
    (2019-05-13) Niu, Xun; Liu, Yating; King, Alistair W.T.; Hietala, Sami; Pan, Hui; Rojas, Orlando J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Alternatives to petroleum-based plastics are of great significance not only from the point of view of their scientific and practical impact but to reduce the environmental footprint. Inspired by the composition and structure of wood's cell walls, we used phenolic acids to endow cellulosic fibers with new properties. The fiber dissolution and homogeneous modification were performed with a recyclable ionic liquid (IL) (tetrabutylammonium acetate ([N 4444 ][OAc]):dimethyl sulfoxide) to attain different levels of reaction activity for three phenolic acids (p-hydroxybenzoic acid, vanillic acid, and syringic acid). The successful autocatalytic Fischer esterification reaction was thoroughly investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, elemental analysis, and nuclear magnetic resonance spectroscopy ( 13 C CP-MAS, diffusion-edited 1 H NMR and multiplicity-edited heteronuclear single quantum coherence). Control of the properties of cellulose in the dispersed state, welding, and IL plasticization were achieved during casting and recrystallization to the cellulose II crystalline allomorph. Films of cellulose carrying grafted acids were characterized with respect to properties relevant to packaging materials. Most notably, despite the low degree of esterification (DS < 0.25), the films displayed a remarkable strength (3.5 GPa), flexibility (strains up to 35%), optical transparency (>90%), and water resistance (WCA ∼90°). Moreover, the measured water vapor barrier was found to be similar to that of poly(lactic acid) composite films. Overall, the results contribute to the development of the next-generation green, renewable, and biodegradable films for packaging applications.
  • Solution-state nuclear magnetic resonance spectroscopy of crystalline cellulosic materials using a direct dissolution ionic liquid electrolyte
    (2023-07) Fliri, Lukas; Heise, Katja; Koso, Tetyana; Todorov, Aleksandar R.; del Cerro, Daniel Rico; Hietala, Sami; Fiskari, Juha; Kilpeläinen, Ilkka; Hummel, Michael; King, Alistair W.T.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Owing to its high sustainable production capacity, cellulose represents a valuable feedstock for the development of more sustainable alternatives to currently used fossil fuel-based materials. Chemical analysis of cellulose remains challenging, and analytical techniques have not advanced as fast as the development of the proposed materials science applications. Crystalline cellulosic materials are insoluble in most solvents, which restricts direct analytical techniques to lower-resolution solid-state spectroscopy, destructive indirect procedures or to ‘old-school’ derivatization protocols. While investigating their use for biomass valorization, tetralkylphosphonium ionic liquids (ILs) exhibited advantageous properties for direct solution-state nuclear magnetic resonance (NMR) analysis of crystalline cellulose. After screening and optimization, the IL tetra-n-butylphosphonium acetate [P4444][OAc], diluted with dimethyl sulfoxide-d 6, was found to be the most promising partly deuterated solvent system for high-resolution solution-state NMR. The solvent system has been used for the measurement of both 1D and 2D experiments for a wide substrate scope, with excellent spectral quality and signal-to-noise, all with modest collection times. The procedure initially describes the scalable syntheses of an IL, in 24–72 h, of sufficient purity, yielding a stock electrolyte solution. The dissolution of cellulosic materials and preparation of NMR samples is presented, with pretreatment, concentration and dissolution time recommendations for different sample types. Also included is a set of recommended 1D and 2D NMR experiments with parameters optimized for an in-depth structural characterization of cellulosic materials. The time required for full characterization varies between a few hours and several days.
  • Spatioselective surface chemistry for the production of functional and chemically anisotropic nanocellulose colloids
    (2022-11-28) Heise, Katja; Koso, Tetyana; King, Alistair W.T.; Nypelö, Tiina; Penttilä, Paavo; Tardy, Blaise L.; Beaumont, Marco
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    Maximizing the benefits of nanomaterials from biomass requires unique considerations associated with their native chemical and physical structure. Both cellulose nanofibrils and nanocrystals are extracted from cellulose fibers via a top-down approach and have significantly advanced materials chemistry and set new benchmarks in the last decade. One major challenge has been to prepare defined and selectively modified nanocelluloses, which would, e.g., allow optimal particle interactions and thereby further improve the properties of processed materials. At the molecular and crystallite level, the surface of nanocelluloses offers an alternating chemical structure and functional groups of different reactivity, enabling straightforward avenues towards chemically anisotropic and molecularly patterned nanoparticles via spatioselective chemical modification. In this review, we will explain the influence and role of the multiscale hierarchy of cellulose fibers in chemical modifications, and critically discuss recent advances in selective surface chemistry of nanocelluloses. Finally, we will demonstrate the potential of those chemically anisotropic nanocelluloses in materials science and discuss challenges and opportunities in this field.
  • Stable glycosylamines at the reducing ends of cellulose nanocrystals
    (2023-08-07) Xia, Jingwen; Koso, Tetyana; Heise, Katja; Fliri, Lukas; Ressouche, Emilie; Majoinen, Johanna; Kostiainen, Mauri A.; Hietala, Sami; Hummel, Michael; Aseyev, Vladimir; Kilpeläinen, Ilkka; King, Alistair W.T.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The reaction of reducing end groups in cellulose nanocrystals with dodecylamine was examined. Using a direct-dissolution solution-state NMR protocol, the regioselective formation of glucosylamines was shown. This provides an elegant approach to sustainably functionalize these bio-based nanomaterials, that may not require further reduction to more stable secondary amines.
  • A study of the decomposition products of furfural, xylose and isophorone using NMR
    (2019-03-24) Gomez Millan, Gerardo; King, Alistair W.T.; Llorca, Jordi; Sixta, Herbert
     A4 Artikkeli konferenssijulkaisussa
    In recent years we have witness lots of activity to upgrade sugars contained in lignocellulosic biomass into ethanol and other value-added chemicals. An interesting catalytic route, namely the dehydration of sugars (pentoses and hexoses found in lignocellulose) to furans, is considered one of the most promising routes for the production of platform chemicals and fuels [1]. One attractive furanic compound, furfural (FUR), has been identified as a direct or indirect feedstock to more than 80 chemicals [2,3]. The current FUR production uses mineral acids at approximately 200 °C, providing around 50 mol% yield [4]. Low yields in this process are mainly due to FUR decomposition with other compounds via resinification and condensation producing insoluble polymers (humins) [5]. A practical way to inhibit the formation of humins is to extract the FUR instantaneously from the aqueous solution into an organic phase [6]. In this study, the production of FUR from xylose was carried out using a biphasic batch reaction system. Isophorone was used to extract FUR from the aqueous phase to enhance the overall FUR yield by limiting its degradation. Due to their water-immiscibility nature, this organic solvent do not require salt addition, which is a significant advantage over other water-miscible organic solvents. The effect of time, temperature and organic-to-aqueous ratio on xylose conversion and FUR yield were investigated. Experiments conducted at three temperatures (170, 190 and 210 °C) were studied in a stirred microwave-assisted batch reactor, which established the optimal conditions to obtain the highest FUR yield. The maximum FUR yields obtained from xylose was 48 mol% when using isophorone with an aqueous to organic phase ratio of 1:1. In the present work from isophorone, it demonstrates a low selectivity towards FUR (and thus low FUR yield) with decomposition. This suggests that FUR undergoes decomposition reactions, potentially including isophorone as a co-reactant. Alternatively, the rate of degradation of FUR may be increased by an increasing content of water at temperatures approaching 200 °C. These possibilities were investigated by NMR analysis of the degradation of FUR: isophorone molar ratios of 1:1 and 1:10 at 190 °C over 30 min (Figure 1). Potential mechanisms for this degradation might be, for example, Diels-Alder cycloaddition (isophorone as hindered dienophile), Aldol condensation (isophorone C6 reacting as nucleophile at the FUR aldehyde), Baylis-Hillman reaction (isophorone C2 reacting as nucleophile at the FUR aldehyde) and Michael addition (isophorone C3 as α-β unsaturated electrophile). Other reactivity may of course be possible [7-9].