| 1. |
- Petschacher, P., et al.
(author)
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Dynamic and Static Assembly of Sulfated Cellulose Nanocrystals with Alkali Metal Counter Cations
- 2022
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In: Nanomaterials. - : MDPI AG. - 2079-4991. ; 12
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Journal article (peer-reviewed)abstract
- Sulfate groups on cellulose particles such as cellulose nanocrystals (CNCs) provide colloidal stability credit to electrostatic repulsion between the like-charged particles. The introduction of sodium counter cations on the sulfate groups enables drying of the CNC suspensions without irreversible aggregation. Less is known about the effect of other counter cations than sodium on extending the properties of the CNC particles. Here, we introduce the alkali metal counter cations, Li+, Na+, K+, Rb+, and Cs+, on sulfated CNCs without an ion exchange resin, which, so far, has been a common practice. We demonstrate that the facile ion exchange is an efficient method to exchange to any alkali metal cation of sulfate half esters, with exchange rates between 76 and 89%. The ability to form liquid crystalline order in rest was observed by the presence of birefringence patterns and followed the Hofmeister series prediction of a decreasing ability to form anisotropy with an increasing element number. However, we observed the K-CNC rheology and birefringence as a stand-out case within the series of alkali metal modifications, with dynamic moduli and loss tangent indicating a network disruptive effect compared to the other counter cations, whereas observation of the development of birefringence patterns in flow showed the absence of self- or dynamically-assembled liquid crystalline order.
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| 2. |
- Wojno, Sylwia, 1990, et al.
(author)
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Phase transitions of cellulose nanocrystal suspensions from nonlinear oscillatory shear
- 2022
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In: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 29:7, s. 3655-3673
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Journal article (peer-reviewed)abstract
- Cellulose nanocrystals (CNCs) self- assemble in water suspensions into liquid crystalline assemblies. Here, we elucidate the microstructural changes associated with nonlinear deformations in (2–9 wt%) CNC suspensions through nonlinear rheological analysis, that was performed in paral- lel with coupled rheology—polarized light imaging. We show that nonlinear material parameters from Fourier-transform rheology and stress decomposition are sensitive to all CNC phases investigated, i.e. iso- tropic, biphasic and liquid crystalline. This is in con- trast to steady shear and linear viscoelastic dynamic moduli where the three-region behavior and weak strain overshoot cannot distinguish between biphasic and liquid crystalline phases. Thus, the inter-cycle and intra-cycle nonlinear parameters investigated are a more sensitive approach to relate rheological meas- urements to CNC phase behavior.
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| 3. |
- Arumughan, Vishnu, 1994, et al.
(author)
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Calcium Ion-Induced Structural Changes in Carboxymethylcellulose Solutions and Their Effects on Adsorption on Cellulose Surfaces
- 2022
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 23:1, s. 47-56
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Journal article (peer-reviewed)abstract
- The adsorption of carboxymethylcellulose (CMC) on cellulose surfaces is one of the most studied examples of the adsorption of an anionic polyelectrolyte on a like-charged surface. It has been suggested that divalent ions can act as a bridge between CMC chains and the surface of cellulose and enhance the CMC adsorption: they can, however, also alter the structure of CMCs in the solution. In previous investigations, the influence of cations on solution properties has been largely overlooked. This study investigates the effect of Ca2+ ions on the properties of CMC solutions as well as the influence on cellulose nanofibers (CNFs), which was studied by dynamic light scattering and correlated with the adsorption of CMC on a cellulose surface probed using QCMD. The presence of Ca2+ facilitated the multichain association of CMC chains and increased the hydrodynamic diameter. This suggests that the adsorption of CMCs at high concentrations of CaCl2 is governed mainly by changes in solution properties rather than by changes in the cellulose surface. Furthermore, an entropy-driven mechanism has been suggested for the adsorption of CMC on cellulose. By comparing the adsorption of CMC from H2O and D2O, it was found that the release of water from the cellulose surface is driving the adsorption of CMC.
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| 4. |
- Heise, Katja, et al.
(author)
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Spatioselective surface chemistry for the production of functional and chemically anisotropic nanocellulose colloids
- 2022
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7496 .- 2050-7488. ; 121
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Research review (peer-reviewed)abstract
- 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.
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| 5. |
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| 6. |
- Nypelö, Tiina, 1982
(author)
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Magnetic cellulose: does extending cellulose versatility with magnetic functionality facilitate its use in devices?
- 2022
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In: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7534 .- 2050-7526. ; 10:3, s. 805-818
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Research review (peer-reviewed)abstract
- Magnetism is certainly one of the most intriguing properties of materials. It provides a means for manipulating macroscopic and microscopic positioning and alignment of materials and is a characteristic that is essential for the creation of numerous devices and appliances. Cellulose is a renewable resource that encompasses a diverse portfolio of material hierarchies: the cellulose molecule, molecular clusters, fibrils, fibers, films, and wood products. Cellulose is exploited in materials due to its impressive intrinsic properties of non-toxicity, low density, and low cost as well as due to the extraordinary material properties of thermal stability and strength. However, many devices operate on electrical or magnetic signals, a functionality that cellulose lacks. To exploit cellulose in such applications, cellulose is often modified by ferromagnetic particles. Ferromagnetic cellulose fibers are not only demonstrated for separation of biomolecules and environmental accumulations but also in electrical textiles, loudspeakers, magnetic shielding, and optical and medical devices. This review focuses on presenting the current selection of methods for rendering cellulose magnetic; its demonstrated use in devices; and an outlook on the challenges, application, and gaps in knowledge of creating the requisite materials.
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| 7. |
- Palasingh, Chonnipa, 1992, et al.
(author)
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Modification of xylan via an oxidation–reduction reaction
- 2022
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In: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 292
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Journal article (peer-reviewed)abstract
- Xylan is a biopolymer readily available from forest resources. Various modification methods, including oxidation with sodium periodate, have been shown to facilitate the engineering applications of xylan. However, modification procedures are often optimized for semicrystalline high molecular weight polysaccharide cellulose rather than for lower molecular weight and amorphous polysaccharide xylan. This paper elucidates the procedure for the periodate oxidation of xylan into dialdehyde xylan and its further reduction into a dialcohol form and is focused on the modification work up. The oxidation–reduction reaction decreased the molecular weight of xylan while increased the dispersity more than 50%. Unlike the unmodified xylan, all the modified grades could be solubilized in water, which we see essential for facilitating the future engineering applications of xylan. The selection of quenching and purification procedures and pH-adjustment of the reduction step had no significant effect on the degree of oxidation, molecular weight and only a minor effect on the hydrodynamic radius in water. Hence, it is possible to choose the simplest oxidation-reduction route without time consuming purification steps within the sequence.
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| 8. |
- Schaubeder, Jana B., et al.
(author)
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Xylan-cellulose thin film platform for assessing xylanase activity
- 2022
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In: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 294
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Journal article (peer-reviewed)abstract
- Enzymatic degradation of plant polysaccharide networks is a complex process that involves disrupting an intimate assembly of cellulose and hemicelluloses in fibrous matrices. To mimic this assembly and to elucidate the efficiency of enzymatic degradation in a rapid way, models with physicochemical equivalence to natural systems are needed. Here, we employ xylan-coated cellulose thin films to monitor the hydrolyzing activity of an endo-1,4-β-xylanase. In situ surface plasmon resonance spectroscopy (SPRS) revealed a decrease in xylan areal mass ranging from 0.01 ± 0.02 to 0.52 ± 0.04 mg·m−2. The extent of digestion correlates to increasing xylanase concentration. In addition, ex situ determination of released monosaccharides revealed that incubation time was also a significant factor in degradation (P > 0.01). For both experiments, atomic force microscopy confirmed the removal of xylans from the cellulose thin films. We provide a new model platform that offers nanoscale sensitivity for investigating biopolymer interactions and their susceptibility to enzymatic hydrolysis.
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