| 1. |
- Magnani, Chiara, et al.
(författare)
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Green Topochemical Esterification Effects on the Supramolecular Structure of Chitin Nanocrystals: Implications for Highly Stable Pickering Emulsions
- 2022
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 5:4, s. 4731-4743
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Tidskriftsartikel (refereegranskat)abstract
- In nature, chitin is organized in hierarchical structures composed of nanoscale building blocks that show outstanding mechanical and optical properties attractive for nanomaterial design. For applications that benefit from a maximized interface such as nanocomposites and Pickering emulsions, individualized chitin nanocrystals (ChNCs) are of interest. However, when extracted in water suspension, their individualization is affected by ChNC self-assembly, requiring a large amount of water (above 90%) for ChNC transport and stock, which limits their widespread use. To master their individualization upon drying and after regeneration, we herein report a waterborne topochemical one-pot acid hydrolysis/Fischer esterification to extract ChNCs from chitin and simultaneously decorate their surface with lactate or butyrate moieties. Controlled reaction conditions were designed to obtain nanocrystals of a comparable aspect ratio of about 30 and a degree of modification of about 30% of the ChNC surface, under the rationale to assess the only effect of the topochemistry on ChNC supramolecular organization. The rheological analysis coupled with polarized light imaging shows how the nematic structuring is hindered by both surface ester moieties. The increased viscosity and elasticity of the modified ChNC colloids indicate a gel-like phase, where typical ChNC clusters of liquid crystalline phases are disrupted. Pickering emulsions have been prepared from lyophilized nanocrystals as a proof of concept. Our results demonstrate that only the emulsions stabilized by the modified ChNCs have excellent stability over time, highlighting that their individualization can be regenerated from the dry state.
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| 2. |
- Wang, Xueting, 1991, et al.
(författare)
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Methane Adsorption and Methanol Desorption for Copper Modified Boron Silicate
- 2018
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 8:63, s. 36369-36374
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Tidskriftsartikel (refereegranskat)abstract
- Boron silicate (BS) with a chabazite framework structure was synthesised using a direct route and rigorously characterized before it was ion-exchanged with copper to form Cu-BS. Employing in situ infrared spectroscopy, we show that Cu-BS is capable of oxidising methane to methoxy species and methanol interacts with the boron sites without deprotonation.
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| 3. |
- Andersson, Markus, 1981, et al.
(författare)
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Vinylimidazole copolymers: coordination chemistry, solubility, and cross-linking as function of Cu2+ and Zn2+ complexation
- 2011
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Ingår i: Colloid and Polymer Science. - : Springer Science and Business Media LLC. - 0303-402X .- 1435-1536. ; 289:12, s. 1361-1372
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Tidskriftsartikel (refereegranskat)abstract
- P(1-VIm-co-MMA) copolymers with 4 or 44 wt.% 1-VIm (abbreviated PVM-4 and PVM-44) where polymerized from 1-VIm (1-vinylimidazole) and methylmethacrylate with azobisisobutyronitrile as initiator and reacted with either Cu(2+) or Zn(2+). The resulting coordinated polymer complexes were studied using ICP-AES, CP/MAS (13)C NMR, conductivity measurements, vibrational spectroscopy (mid-FTIR and far-FTIR), DSC, and EPR. It was established by ICP-AES, CP/MAS (13)C NMR, conductivity, mid-FTIR and EPR measurements that the transition metal ions in the complexes were exclusively coordinated by the imidazole ligand. The coordination geometry is square planar with regard to Cu(II) complexes. The strong interaction between the polymeric imidazole ligand and the transition metal ion cross-links the system, resulting in augmentation of T (g) (the glass transition temperature), especially for copolymers with high relative amount of 1-VIm. The effect of changing metal ion is more complicated and depends on both the strength of the coordinate interaction as well as the coordination number. The solubility of the coordinate polymer complex in conventional solvents is low due to the coordinate cross-links. However, the coordinate polymer complexes are soluble in strongly coordinating solvents such as acetonitrile and dimethylsulfoxide.
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| 4. |
- Avella, Angelica, 1995, et al.
(författare)
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Reactive melt crosslinking of cellulose nanocrystals/poly(ε-caprolactone) for heat-shrinkable network
- 2022
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Ingår i: Composites Part A: Applied Science and Manufacturing. - : Elsevier BV. - 1359-835X. ; 163
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Tidskriftsartikel (refereegranskat)abstract
- Focusing on the challenge of non-biodegradable plastics replacement, we propose a design for peroxide-initiated crosslinking of biodegradable poly(ε-caprolactone) (PCL) and renewable cellulose nanocrystals (CNCs) bionanocomposites. An industrially scalable water-assisted reactive melt-processing (REx) is studied to explore the hypothesis of synergy between simultaneous effects of water on improving CNC dispersion and boosting PCL branching/crosslinking. We demonstrate that the melt processing control enables the preparation of targeted thermoplastic/thermoset bionanocomposites with gel content up to ≈ 40 %, identified as the limit of their melt-processability. Structural characterization reveals that ≈ 70 wt% of the initial CNC content is irreversibly incorporated in a percolating network, enhancing the crosslinked bionanocomposites properties. The bionanocomposites' complex viscosity and elastic character increase with the gel content, thus improving PCL melt performance. Furthermore, the irreversible entrapment of CNCs in the 3D percolating network provides heat-shrinkability, indicating a potential of the reacted bionanocomposites for heat-triggered shape-memory.
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| 5. |
- Bengtsson, Jenny, et al.
(författare)
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Chemical Recycling of a Textile Blend from Polyester and Viscose, Part II : Mechanism and Reactivity during Alkaline Hydrolysis of Textile Polyester
- 2022
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Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 14:11
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Tidskriftsartikel (refereegranskat)abstract
- Chemical recycling of textiles holds the potential to yield materials of equal quality and value as products from virgin feedstock. Selective depolymerization of textile polyester (PET) from regenerated cellulose/PET blends, by means of alkaline hydrolysis, renders the monomers of PET while cellulose remains in fiber form. Here, we present the mechanism and reactivity of textile PET during alkaline hydrolysis. Part I of this article series focuses on the cellulose part and a possible industrialization of such a process. The kinetics and reaction mechanism for alkaline hydrolysis of polyester packaging materials or virgin bulk polyester are well described in the scientific literature; however, information on depolymerization of PET from textiles is sparse. We find that the reaction rate of hydrolysis is not affected by disintegrating the fabric to increase its surface area. We ascribe this to the yarn structure, where texturing and a low density assures a high accessibility even without disintegration. The reaction, similar to bulk polyester, is shown to be surface specific and proceeds via endwise peeling. Finally, we show that the reaction product terephthalic acid is pure and obtained in high yields. © 2022 by the authors.
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| 6. |
- Ghaffari, Roujin, 1994, et al.
(författare)
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Effect of alkalinity on the diffusion of solvent-fractionated lignin through cellulose membranes
- 2023
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 30:6, s. 3685-3698
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Tidskriftsartikel (refereegranskat)abstract
- Mass transport of liberated lignin fragments from pits and fiber walls into black liquor is considered a determining step in the delignification process. However, our current understanding of the diffusion of lignin through cellulose and the influential parameter on this process is very limited. A comprehensive and detailed study of lignin mass transport through cellulosic materials is, therefore, of great importance. In this study, diffusion cell methodology is implemented to systematically investigate the transport of fractionated kraft lignin molecules through model cellulose membranes. Pulping is a complex process and lignin is very heterogenous material therefore to perform a more detailed study on lignin diffusion, we included an additional solvent fractionation step. One of the benefits of this method is that the setup can be adjusted to various experimental conditions allowing the complex chemical reactions occurring during pulping, which would affect the mass transfer of lignin, to be avoided. Here, the effects of the alkalinity of the aqueous solution and molecular weight of the kraft lignin molecules on their diffusion were investigated. Additionally, NMR spectroscopy, size exclusion chromatography, and UV/Vis spectroscopy were used to characterize the starting material and the molecules that passed through the membrane. Lignin molecules detected in the acceptor chamber of the diffusion cells had lower molecular weights, indicating a size fractionation between the donor and acceptor chamber. UV/Vis showed higher concentrations of ionized conjugated kraft lignin molecules in the acceptor chamber, which is a sign of chemical fractionation. This study suggests that the diffusion of lignin through small cellulose pores can be enhanced by decreasing the average molecular weight of the diffusing kraft lignin molecules and increasing alkalinity.
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| 7. |
- Grenda, Kinga, 1989, et al.
(författare)
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An analytical approach to elucidate the architecture of polyethyleneimines
- 2022
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 139:7
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Tidskriftsartikel (refereegranskat)abstract
- Polyethyleneimine (PEI) is a common polymer used in many industrial applications and in research, especially in surface chemistry. It is available in a wide range of molecular weights and different degrees of branching. It is classified as linear or branched and sometimes the term hyperbranched is also used. This description, however, is quite rough, which limits the possibility to correlate the structure of the PEI to its properties. The aim of this study is to provide analytical tools to characterize the polymer at a level of detail not normally provided by the supplier of PEI. To this end, five commercially available polyethyleneimines were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and nuclear magnetic resonance spectroscopy to gain insight into the structure and the functional groups present in the polymers. Quantitative 13C NMR analysis turned out to be particularly useful, revealing the degree of branching of the polymer based on the ratio of primary, secondary, and tertiary amino groups.
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| 8. |
- Gårdebjer, Sofie, 1985, et al.
(författare)
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Solid-state NMR to quantify surface coverage and chain length of lactic acid modified cellulose nanocrystals, used as fillers in biodegradable composites
- 2015
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Ingår i: Composites Science and Technology. - : Elsevier BV. - 0266-3538. ; 107, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- The surface of cellulose nanocrystals (CNC) was chemically modified with polylactic acid. The modification was characterized by infrared spectroscopy, by monitoring the colloidal behavior of CNC in different solvents, and by quantitative analysis using solid-state NMR (ss-NMR). The quantitative analysis showed that grafted PLA chains on average comprised two lactic acid units attached to 48% of all available hydroxyl groups on the surface of the CNC. Both modified and unmodified CNC were incorporated as fillers in three different biodegradable materials: polylactide acid (PLA), poly(lactide-co-glycolide) (PLGA) and poly(3-hydroxybutyrate) (PHB). Composite films with up to 20 wt% of unmodified and modified CNC were produced via solvent casting. Compared to unmodified CNC, the modified CNC showed less aggregation in organic solvents and hydrophobic polymer materials and increased interaction was seen between the polymer and filler after surface modification. Using ss-NMR, our study shows that even as little as two units of PLA assures stabile CNC dispersions in organic solvents and distribute CNC in hydrophobic polymers.
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| 9. |
- Haque, Mohammad Mazharul, 1984, et al.
(författare)
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Exploiting low-grade waste heat to produce electricity through supercapacitor containing carbon electrodes and ionic liquid electrolytes
- 2022
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 403
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Tidskriftsartikel (refereegranskat)abstract
- Low-grade thermal energy harvesting presents great challenges to traditional thermoelectric systems based on the Seebeck effect, the thermogalvanic effect, and the Soret effect due to fixed temperature gradient and low voltage output. In this study, we report an ionic thermoelectric system, essentially a supercapacitor (SC) containing an ionic liquid (IL) electrolyte and activated carbon electrodes, which works on the thermocapacitive effect and does not require any fixed temperature gradient, rather it works in a homogeneously changing temperature. A systematic investigation is carried out on SCs containing two different ILs, 1-Ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl), EMIm TFSI, and 1-Ethyl-3-methylimidazolium acetate, EMIm OAc. A high voltage output of 176 mV is achieved for EMIm TFSI containing SC by exposing just to 60 °C environment. Moreover, a large voltage of 502 mV is recovered from the SC upon subjecting to heat after one electrical charge/discharge cycle. A system containing two SCs in series demonstrates a significant voltage of 947 mV. The observed performance difference between the two ILs is rationalized in terms of the extent of asymmetry in the interfaces of the electrical double layer that essentially originates from different diffusivity of individual ions. The mechanism can be applied to a plethora of ILs to exploit low-grade heat to store electricity without a fixed temperature gradient, opening up the possibility to merge different scientific communities and enrich this rising research field.
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| 10. |
- Hasani, Merima, 1978, et al.
(författare)
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Nano-cellulosic materials: The impact of water on their dissolution in DMAc/LiCl
- 2013
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 98:2, s. 1565-1572
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Tidskriftsartikel (refereegranskat)abstract
- The dissolution behaviour of disassociated cellulosic materials in N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) was investigated. The parameters monitored were chromatographic elution profiles and recovered mass by means of gel permeation chromatography (GPC) with RI detection. In order to elucidate the impact of the disassembly on cellulosic fibres, comparative studies were performed with the non-disassociated cellulose counterparts. The importance of the presence of water was addressed by Karl Fischer titration and solvent exchange experiments. Morphological changes during the dissolution process were studied by scanning electron microscopy (SEM). Dissolution of fibrillated cellulosic materials is impeded compared to the non-fibrillated material. This is a consequence of the high-surface-area fibrils prone to retain high amounts of water. Dissolution behaviour of nano-crystalline cellulosic materials appeared to be source-dependent. Due to the absence of entangled networks, these materials retain only water bound at the surface of the nano-crystallites, indicative of both the exposed surface area and solubility. The small cellulose nano-particles extracted from dissolving pulp show lower solubility compared to the large NCC particles from cotton.
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| 11. |
- Idström, Alexander, 1983, et al.
(författare)
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13C NMR assignments of regenerated cellulose from solid-state 2D NMR spectroscopy
- 2016
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 151, s. 480-487
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Tidskriftsartikel (refereegranskat)abstract
- From the assignment of the solid-state 13C NMR signals in the C4 region, distinct types of crystalline cellulose, cellulose at crystalline surfaces, and disordered cellulose can be identified and quantified. For regenerated cellulose, complete 13C assignments of the other carbon regions have not previously been attainable, due to signal overlap. In this study, two-dimensional (2D) NMR correlation methods were used to resolve and assign 13C signals for all carbon atoms in regenerated cellulose. 13C-enriched bacterial nanocellulose was biosynthesized, dissolved, and coagulated as highly crystalline cellulose II. Specifically, four distinct 13C signals were observed corresponding to conformationally different anhydroglucose units: two signals assigned to crystalline moieties and two signals assigned to non-crystalline species. The C1, C4 and C6 regions for cellulose II were fully examined by global spectral deconvolution, which yielded qualitative trends of the relative populations of the different cellulose moieties, as a function of wetting and drying treatments.
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| 12. |
- Idström, Alexander, 1983, et al.
(författare)
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CP/MAS C-13 NMR study of pulp hornification using nanocrystalline cellulose as a model system
- 2013
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 92:1, s. 881-884
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Tidskriftsartikel (refereegranskat)abstract
- The hornification process of paper pulp was investigated using solid-state C-13 NMR spectroscopy. Nanocrystalline cellulose was used to serve as a model system of the crystalline parts of the fibrils in pulp fibers. Characterization of the nanocrystalline cellulose dimensions was carried out using scanning electron microscopy. The samples were treated by drying and wetting cycles prior to NMR analysis where the hornification phenomenon was recorded by spectral changes of the cellulose C-4 carbon signals. An increase of the crystalline signal and a decrease of the signals corresponding to the accessible amorphous domains were found for both paper pulp and nanocrystalline cellulose. These spectral changes grew stronger with repeating drying and wetting cycles. The results show that cellulose co-crystallization contribute to hornification. Another conclusion is that the surfaces of higher hydrophobicity in cellulose fibrils have an increased preference for aggregation.
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| 13. |
- Idström, Alexander, 1983
(författare)
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Investigating cellulose structure using solid-state NMR spectroscopy
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose is the most abundant polymer in nature and it is an important constituent in most flowers, trees, and even some animals. Cellulose has an established use in many important products, such as textile fibers, paper and paperboard, and recently new applications have received increased attention. The crystalline parts of the cellulose wood fiber can be extracted and this material can be used for applications such as forming thin films or as stabilizers in emulsions. New and more environmentally friendly processes to dissolve cellulose and produce textile fibers are also of interest. However, both native and regenerated cellulose build up complicated supramolecular structures that are, to some extent, still not completely resolved. In order to be able to utilize the cellulose material fully, additional knowledge of the material is needed. In the work covered in this thesis, solid-state NMR was used to gain information of the supramolecular structure of cellulose. Measurements were conducted on both native and regenerated cellulose, exposed to a range of different treatments. Using the 1D solid-state NMR spectrum, the effects on the material after a certain treatment could be followed and elucidated. During the production of regenerated cellulose, the structure of the material was altered by changing the properties of either the solvent or the coagulant, changing the initial cellulose concentration, or by post-treatment, e.g. drying and re-wetting. This latter process induces an irreversible pore collapse, called hornification. This phenomenon was seen for both native and regenerated cellulose and it was concluded from the studies that co-crystallization contributes to hornification. Using 2D solid-state NMR correlation spectroscopy, a full chemical shift assignment of the 1D NMR spectrum of regenerated cellulose was obtained. This assignment made it possible to follow treatments of the material from the full solid-state NMR spectrum. Using the chemical shift assignment, a global spectral deconvolution could be applied on the 1D spectrum of regenerated cellulose, making it possible to, with increased accuracy, determine the crystallinity of the material.
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| 14. |
- Idström, Alexander, 1983
(författare)
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Investigating structural changes of cellulose using NMR spectroscopy
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis solid-state NMR and NMR cryoporometry were used to gain information of the structure of cellulose. Measurements were conducted on both native and regenerated cellulose, exposed to a range of different treatments. The impact of co-crystallization for hornification was investigated using nanocrystalline cellulose (NCC) as a model system of the crystalline parts of the pulp fiber. Signs of hornification, in form of an irreversible pore collapse and decreased amount of surface area were seen both for native and regenerated cellulose when exposing the samples to drying treatment and it was concluded that co-crystallization could contribute to hornification. In addition, it was proposed that elements of higher hydrophobicity in native cellulose fibrils have an increased preference for aggregation. Both the dissolution and coagulation steps were found to be of importance during regeneration of cellulose. By altering the coagulation media it was possible to form regenerated cellulose ranging from a mainly crystalline sample using water as coagulation medium to an almost non-crystalline sample using an alcohol. It was concluded that water present in the solvent during dissolution could affect the properties of the regenerated cellulose. However, with a small addition of water an apparent maximum conversion to crystalline cellulose II was found which implies that the cellulose has been dissolved to a higher extent in the dissolution step. At high concentration of water the conversion to cellulose II was completely inhibited. The initial cellulose concentration was also concluded to be of importance. At high cellulose concentration the conversion was largely restricted to a semi-crystalline/non-crystalline material.
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| 15. |
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| 16. |
- Janewithayapun, Ratchawit, 1998, et al.
(författare)
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Nanostructures of etherified arabinoxylans and the effect of arabinose content on material properties
- 2024
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 331
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Tidskriftsartikel (refereegranskat)abstract
- To further our understanding of a thermoplastic arabinoxylan (AX) material obtained through an oxidation-reduction-etherification pathway, the role of the initial arabinose:xylose ratio on the material properties was investigated. Compression molded films with one molar substitution of butyl glycidyl ether (BGE) showed markedly different tensile behaviors. Films made from low arabinose AX were less ductile, while those made from high arabinose AX exhibited elastomer-like behaviors. X-ray scattering confirmed the presence of nanostructure formation resulting in nano-domains rich in either AX or BGE, from side chain grafting. The scattering data showed variations in the presence of ordered structures, nano-domain sizes and their temperature response between AX with different arabinose contents. In dynamic mechanical testing, three transitions were observed at approximately −90 °C, −50 °C and 80 °C, with a correlation between samples with more structured nano-domains and those with higher onset transition temperatures and lower storage modulus decrease. The mechanical properties of the final thermoplastic AX material can therefore be tuned by controlling the composition of the starting material.
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| 17. |
- Khan, Ziyauddin, et al.
(författare)
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Mass Transport in “Water-in-Polymer Salt” Electrolytes
- 2023
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 35, s. 6382-6395
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Tidskriftsartikel (refereegranskat)abstract
- “Water-in-polymer salt” electrolytes (WiPSEs) based on potassium polyacrylate (PAAK) belong to a new family of “water-in-salt” electrolytes that is envisioned as a potential solution for large-scale supercapacitors to balance the electric grid at short time scales. The WiPSEs display a broad electrochemical stability window up to 3 V, yet they are nonflammable and provide high ionic conductivity (100 mS/cm) as required in high-power devices. However, the transport of matter in PAAK-based WiPSEs has not been studied. In this work, we have extensively characterized PAAK by spectroscopic methods such as Raman spectroscopy and NMR diffusometry to determine the state of water and elucidate the mechanism of ionic transport as well as its interplay with water and polymer chain dynamics, which reveals that a significant proportion of the transport in WiPSEs is attributed to hydrated cations. The results are further supported by molecular dynamics (MD) simulations. Finally, the potential of WiPSEs based on PAAK is demonstrated in an activated carbon-based supercapacitor operating up to 2 V with reasonable self-discharge. This proof of concept shows promise for low-cost and large-scale supercapacitors.
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| 18. |
- Kmezik, Cathleen, 1991, et al.
(författare)
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A polysaccharide utilization locus from the gut bacterium Dysgonomonas mossii encodes functionally distinct carbohydrate esterases.
- 2021
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Ingår i: The Journal of biological chemistry. - : Elsevier BV. - 1083-351X .- 0021-9258. ; 296
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Tidskriftsartikel (refereegranskat)abstract
- The gut microbiota plays a central role in human health by enzymatically degrading dietary fiber and concomitantly excreting short chain fatty acids that are associated with manifold health benefits. The polysaccharide xylan is abundant in dietary fiber but non-carbohydrate decorations hinder efficient cleavage by glycoside hydrolases (GHs) and need to be addressed by carbohydrate esterases (CEs). Enzymes from carbohydrate esterase families 1 and 6 (CE1 & 6) perform key roles in xylan degradation by removing feruloyl and acetate decorations, yet little is known about these enzyme families especially with regards to their diversity in activity. Bacteroidetes bacteria are dominant members of the microbiota and often encode their carbohydrate-active enzymes in multi-gene polysaccharide utilization loci (PULs). Here we present the characterization of three CEs found in a PUL encoded by the gut Bacteroidete Dysgonomonas mossii. We demonstrate that the CEs are functionally distinct, with one highly efficient CE6 acetyl esterase and two CE1 enzymes with feruloyl esterase activities. One multidomain CE1 enzyme contains two CE1 domains: an N-terminal domain feruloyl esterase, and a C-terminal domain with minimal activity on model substrates. We present the structure of the C-terminal CE1 domain with the carbohydrate binding module that bridges the two CE1 domains, as well as a complex of the same protein fragment with methyl ferulate. The investment of D. mossii in producing multiple CEs suggests that improved accessibility of xylan for GHs as well as cleavage of covalent polysaccharide-polysaccharide and lignin-polysaccharide bonds are important enzyme activities in the gut environment.
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| 19. |
- Llacer Navarro, Saül, 1990, et al.
(författare)
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The effect of sulfate half-ester groups on cellulose nanocrystal periodate oxidation
- 2021
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 28:15, s. 9633-9644
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Tidskriftsartikel (refereegranskat)abstract
- Periodate oxidation introduces aldehyde functionality to cellulose. The use of dialdehyde cellulose has been demonstrated for crosslinking and as a chemical intermediate towards functionalized cellulose. Commercially available cellulose nanocrystals (CNCs) typically carry a surface sulfate half-ester functionality, which results from their manufacture via sulfuric acid hydrolysis and subsequent esterification. The sulfate half-ester group is a bulky group carrying a net negative charge above pH 2 that modifies the colloidal and electro-chemical properties of the CNCs. Periodate oxidation is regioselective to the bond between carbons in positions 2 and 3 in the anhydroglucose unit while the sulfate half-ester groups are mostly considered to be located in carbon in position 6. This regioselectivity could be the reason why the role played by the sulfate half-ester group on modification by periodate oxidation has not previously been elucidated. Here, the influence of the sulfate half-ester on the oxidation of CNCs, which is shown to steer the oxidation kinetics and the properties of the resulting materials, is studied. Conventional physicochemical analysis of the oxidant consumption is accompanied by elemental analysis, Fourier-transform infrared, X-ray photoelectron and solid-state nuclear magnetic resonance spectroscopy, and wide-angle x-ray scattering analyses; the zeta potential is used to characterize the colloidal properties of the suspensions and atomic force microscopy for determining particle dimensions. The presence of the sulfate half-ester group decreases the rate of oxidation. However, the content of the sulfate half-ester groups decreases when degree of oxidation reaches approx. 50%. We demonstrate that the CNC surfaces are affected by the oxidation beyond the C2–C3 bond cleavage: insight into the kinetics of the oxidation process is a prerequisite for optimizing CNC oxidation.
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| 20. |
- Lundin, Filippa, 1992, et al.
(författare)
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Ion Dynamics and Nanostructures of Diluted Ionic Liquid Electrolytes
- 2022
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:38, s. 16262-16271
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Tidskriftsartikel (refereegranskat)abstract
- Diluted ionic liquid electrolytes are promising candidates in next-generation batteries enabling the implementation of lithium metal anodes. The diluent should fully mix with the ionic liquid while not interacting with the Li ions to preserve the ionic liquid character, which is beneficial for Li-metal electrode stability. We report on the influence of a hydrofluoroether (HFE) diluent on ion dynamics and nanostructure of an ionic liquid electrolyte. We show that the ionic liquid and the diluent are fully miscible and that the solvation structure of the Li ions is not affected by the presence of HFE. The increase in the conductivity by the addition of the diluent is directly related to a decrease in viscosity with faster dynamics of all ionic species. However, the relative increase in mobility is considerably larger for the ionic liquid cation as a result of a preferred interaction with HFE. On the microscopic scale, more complex local non-Gaussian diffusive dynamics are found, faster than what is expected from the self-diffusion coefficient. The relative change of the dynamics with the addition of HFE on macro- and microscopic length scales correlates well, which underlines the connection between the motions probed on different length and time scales.
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| 21. |
- Magnani, Chiara, et al.
(författare)
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Interphase Design of Cellulose Nanocrystals/Poly(hydroxybutyrate- ran-valerate) Bionanocomposites for Mechanical and Thermal Properties Tuning
- 2020
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 21:5, s. 1892-1901
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Tidskriftsartikel (refereegranskat)abstract
- Poly[(3-hydroxybutyrate)-ran-(3-hydroxyvalerate)] (PHBV) is a bacterial polyester with a strong potential as a substitute for oil-based thermoplastics due to its biodegradability and renewability. However, its inherent slow crystallization rate limits its thermomechanical properties and therefore its applications. In this work, surface-modified cellulose nanocrystals (CNCs) have been investigated as green and biosourced nucleating and reinforcing agent for PHBV matrix. Different ester moieties from the CNCs were thereby produced through a green one-pot hydrolysis/Fisher esterification. Beyond the improved dispersion, the CNCs surface esterification affected the thermal and thermomechanical properties of PHBV. The results demonstrate that butyrate-modified CNCs, mimicking the PHBV chemical structure, brought a considerable improvement toward the CNCs/matrix interface, leading to an enhancement of the PHBV thermomechanical properties via a more efficient stress transfer, especially above its glass transition.
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| 22. |
- Maurina Morais, Eduardo, 1989, et al.
(författare)
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Transport Properties of Protic Ionic Liquids Based on Triazolium and Imidazolium: Development of an Air-Free Conductivity Setup
- 2023
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Ingår i: Molecules. - 1420-3049 .- 1420-3049. ; 28:13
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Tidskriftsartikel (refereegranskat)abstract
- The dynamical properties of four protic ionic liquids, based on the ethyltriazolium ([C (Formula presented.) HTr (Formula presented.) ]) and the ethylimidazolium ([C (Formula presented.) HIm]) cation, were investigated. The associated anions were the triflate ([TfO]) and the bistriflimide ([TFSI]). Ionic conductivity values and self-diffusion coefficients were measured and discussed, extending the discussion to the concept of fragility. Furthermore, in order to allow the measurement of the ionic conductivity of very small volumes (<0.5 mL) of ionic liquid under an inert and dry atmosphere, a new setup was developed. It was found that the cation nature strongly affected the transport properties, the [C (Formula presented.) HTr (Formula presented.) ] cation resulting in slower dynamics than the [C (Formula presented.) HIm] one. This was concluded from both conductivity and diffusivity measurements while for both properties, the anion had a lesser effect. By fitting the conductivity data with the Vogel–Fulcher–Tammann (VFT) equation, we could also estimate the fragility of these ionic liquids, which all fell in the range of very fragile glass-forming materials. Finally, the slower dynamics observed in the triazolium-based ionic liquids can be rationalized by the stronger interactions that this cation establishes with both anions, as deduced from the frequency analysis of relevant Raman signatures and density functional theory (DFT) calculations.
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| 23. |
- Olsson, Carina, 1982, et al.
(författare)
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Effect of methylimidazole on cellulose/ionic liquid solutions and regenerated material therefrom
- 2014
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 49:9, s. 3423-3433
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose, especially wood-based cellulose, is increasingly important for making everyday materials such as man-made-regenerated textile fibers, produced via dissolution and subsequent precipitation. In this paper, the effect of cosolvents in ionic liquid-facilitated cellulose dissolution is discussed. Both microcrystalline cellulose and dissolving grade hardwood pulp were studied. Three different cosolvents in combination with ionic liquid were evaluated using turbidity measurements and viscosity. The ionic liquid precursor N-methylimidazole proved to be a promising cosolvent candidate and was thus selected for further studies together with the ionic liquid 1-ethyl-3-methylimidazolium acetate. Results show that dissolution rate can be increased by cosolvent addition, and the viscosity can be significantly reduced. The solutions were stable over time at room temperature and could be converted to regenerated textile fibers with good mechanical properties via airgap spinning and traditional wet spinning. Fibers spun from binary solvents exhibited significantly higher crystallinity than the fibers from neat ionic liquid.
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| 24. |
- Olsson, Carina, 1982, et al.
(författare)
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Influence of water on swelling and dissolution of cellulose in 1-ethyl-3-methylimidazolium acetate
- 2014
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 99, s. 438-446
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Tidskriftsartikel (refereegranskat)abstract
- In this study the effect of residual coagulation medium (water) on cellulose dissolution in an ionic liquid is discussed. Solubility of dissolving grade pulp; HWP and SWP, and microcrystalline cellulose in binary solvents, mixtures of 1-ethyl-3-methyl-imidazolium acetate and water, was investigated by turbidity measurements, light microscopy, rheometry, and CP/MAS 13C-NMR spectroscopy. The viscoelastic properties of the cellulose solutions imply that residual water affect the cellulose dissolution. However, it is not obvious that this always necessarily poses serious drawbacks for the solution properties or that the effects are as severe as previously believed. Turbidity measurements, viscosity data and crystallinity of the regenerated cellulose correlated well and an increased conversion to cellulose II was found at low water and cellulose contents with an apparent maximum of conversion at 2–5 wt% water. At high water content, above 10 wt%, dissolution and conversion was largely inhibited.
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| 25. |
- Palme, Anna, 1986, et al.
(författare)
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Chemical and ultrastructural changes in cotton cellulose induced by laundering and textile use
- 2014
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 21:6, s. 4681-4691
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Tidskriftsartikel (refereegranskat)abstract
- The textile industry is currently under pressure to decrease environmental load related to both the manufacture and the use of textiles. Material recycling may be one of many ways to accomplish such a decrease. Age-induced property changes in cotton textiles are important to understand in order to facilitate the recycling of cotton textiles. Consequently, this study investigates ultrastructural and chemical changes that take place in the cellulose of cotton sheets over a long time period of use and laundering. Ultrastructural changes were studied using water retention value (WRV), specific surface area measurement, scanning electron microscopy and solid state NMR spectroscopy. Chemical changes through measurement of intrinsic viscosity with and without reductive treatment, molecular mass distribution and carboxylate group content. A substantial decrease in mass average molecular mass from 1,320 to 151 kDa was observed when subjecting the sheets to more than 50 launderings. In contrast, only small differences in WRV, in fibril dimensions and crystallinity estimated using solid state NMR spectra, were observed between sheets laundered 2-4 times and more than 50 times. On one hand, the combination of minor laundering effects of WRV and solid state NMR spectra, together with the large decrease in molecular mass are positive indications for the possibility of recycling cotton into regenerated cellulosic fibres. On the other hand, results show that the specific surface area decreased, which implies that the reactivity of cotton cellulose may decrease during long-term use and laundering.
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| 26. |
- Peciulyte, Ausra, 1986, et al.
(författare)
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Cellulolytic enzyme interaction with lignocellulose. Insight to factors limiting enzymatic hydrolysis
- 2013
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Ingår i: Gordon Conference: Cellulosomes, Cellulases & Other Carbohydrate Modifying Enzymes internal database.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Liberation of fermentable soluble sugars from lignocellulosic biomass during the course of enzymatic hydrolysis is the major obstacle to large-scale implementation of biorefineries due to high cost of enzymes. Enzymatic hydrolysis of lignocellulosic biomass is often incomplete and, therefore, it is of great importance to understand the limitations of the process. Among the limitations of enzymatic hydrolysis, structural properties of lignocellulose have an effect of enzymatic hydrolysis efficiency. Currently, there is a lack of direct methods for visualization and quantification of spatial polymer distribution in lignocellulosic biomass and monitoring of interactions between cellulose degrading enzymes and the substrate. The focus of the work was (i) structural characterization of lignocellulose during the course of hydrolysis and (ii) to provide a more detailed understanding of cellulolytic enzyme interaction with lignocellulose. The overall aim was to understand the limitations in enzymatic hydrolysis of lignocellulosic biomass.Enzymatic hydrolysis was studied on industrial-like lignocellulosic and cellulosic substrates, resulting from alkaline pulping and steam explosion of spruce. Enzymatic hydrolysis of lignocellulosic substrates was compared to enzymatic hydrolysis of model cellulosic substrates. Enzymatic hydrolysis of the substrates was performed with commercial enzyme mixture Celluclast 1.5 L and also with designed enzyme mixtures, consisting of mono-component enzymes. The structural properties of the substrates during an incrementing time of hydrolysis were analyzed by solid-state Nuclear Magnetic Resonance (NMR) spectroscopy, Coherent Anti-Strokes Raman Scattering (CARS) and Second Harmonic Generation (SHG) microscopy. Hydrolysis products were verified by High Performance Anion Exchange Chromatography with Pulsed Amperometric Detection (HPAEC-PAD). Dynamics of the hydrolysis was analyzed by Quartz Crystal Microbalance with Dissipation (QCM-D) technique.
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| 27. |
- Peterson, Anna, et al.
(författare)
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Chemical Recycling of a Textile Blend from Polyester and Viscose, Part I : Process Description, Characterization, and Utilization of the Recycled Cellulose
- 2022
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Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 14:12
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Tidskriftsartikel (refereegranskat)abstract
- Material recycling requires solutions that are technically, as well as economically and ecologically, viable. In this work, the technical feasibility to separate textile blends of viscose and polyester using alkaline hydrolysis is demonstrated. Polyester is depolymerized into the monomer terephthalic acid at high yields, while viscose is recovered in a polymeric form. After the alkaline treatment, the intrinsic viscosity of cellulose is decreased by up to 35%, which means it may not be suitable for conventional fiber-to-fiber recycling; however, it might be attractive in other technologies, such as emerging fiber processes, or as raw material for sugar platforms. Further, we present an upscaled industrial process layout, which is used to pinpoint the areas of the proposed process that require further optimization. The NaOH economy is identified as the key to an economically viable process, and several recommendations are given to decrease the consumption of NaOH. To further enhance the ecological end economic feasibility of the process, an increased hydrolysis rate and integration with a pulp mill are suggested.
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| 28. |
- Sörensen Ristinmaa, Amanda, 1992, et al.
(författare)
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Deciphering key stages, compounds, and microorganisms during microbial degradation of spruce bark
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Bark acts as the skin and outer barrier of the tree, protecting it from microbial degradation and environmental stress [1]. The bark is a major forestry waste product, and while it is mainly composed of lignocellulose, it also contains a large amount of so-called extractive compounds, which typically have strong antimicrobial properties [2]. Despite the presence of these extractives, there are microorganisms capable of growing on bark [3]. However, it is currently not known which microorganisms are responsible for this biological degradation, or whether different species dominate different stages of bark degradation. In this study, we have followed a microbial consortium growing on spruce bark for six months. We have analyzed the changes in the material over time using a combination of GC-MS, NMR, and HPAEC-PAD, both regarding extractive and carbohydrate content, and in parallel, we have mapped the microbial community using sequencing. These data enable correlation of the material changes with the variation of the bacterial and fungal population. We found that in the early degradation stages, the community is dominated by a few bacterial taxa, likely due to the antimicrobial properties of the bark. A significant increase in the microbial diversity was correlated with the degradation of resin acids, which thus likely are the main antimicrobial compounds. From one of the early samplings, we isolated one of the dominating organisms — a new Pseudomonas species able to metabolize different types of resin acids — which was phenotypically characterized and whole-genome-sequenced. Our results suggests that the removal of resin acids from spruce bark is a critical step in the bark degradation process, and precedes degradation of carbohydrates and lignin, for which we did not observe major changes. This work forms a basis for understanding of which microorganisms and extractives are key players during microbial bark degradation.
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| 29. |
- Sörensen Ristinmaa, Amanda, 1992, et al.
(författare)
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Resin acids play key roles in shaping microbial communities during degradation of spruce bark
- 2023
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Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The bark is the outermost defense of trees against microbial attack, largely thanks to toxicity and prevalence of extractive compounds. Nevertheless, bark decomposes in nature, though by which species and mechanisms remains unknown. Here, we have followed the development of microbial enrichments growing on spruce bark over six months, by monitoring both chemical changes in the material and performing community and metagenomic analyses. Carbohydrate metabolism was unexpectedly limited, and instead a key activity was metabolism of extractives. Resin acid degradation was principally linked to community diversification with specific bacteria revealed to dominate the process. Metagenome-guided isolation facilitated the recovery of the dominant enrichment strain in pure culture, which represents a new species (Pseudomonas abieticivorans sp. nov.), that can grow on resin acids as a sole carbon source. Our results illuminate key stages in degradation of an abundant renewable resource, and how defensive extractive compounds have major roles in shaping microbiomes.
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| 30. |
- Yang, Yizhou, 1992, et al.
(författare)
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Electroactive Covalent Organic Framework Enabling Photostimulus-Responsive Devices
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:35, s. 16093-16100
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional covalent organic frameworks (2D COFs) feature graphene-type 2D layered sheets but with a tunable structure, electroactivity, and high porosity. If these traits are well-combined, then 2D COFs can be applied in electronics to realize functions with a high degree of complexity. Here, a highly crystalline electroactive COF, BDFamide-Tp, was designed and synthesized. It shows regularly distributed pores with a width of 1.35 nm. Smooth and successive films of such a COF were fabricated and found to be able to increase the conductivity of an organic semiconductor by 103 by interfacial doping. Upon encapsulation of a photoswitchable molecule (spiropyran) into the voids of the COF layer, the resulted devices respond differently to light of different wavelengths. Specifically, the current output ratio after UV vs Vis illumination reaches 100 times, thus effectively creating on and off states. The respective positive and negative feedbacks are memorized by the device and can be reprogrammed by UV/Vis illumination. The reversible photostimulus responsivity and reliable memory of the device are derived from the combination of electroactivity and porosity of the 2D COF. This work shows the capability of 2D COFs in higher-level electronic functions and extends their possible applications in information storage. © 2022 The Authors. Published by American Chemical Society.
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| 31. |
- Zhang, Dongming, et al.
(författare)
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Arabinoxylan supplemented bread: From extraction of fibers to effect of baking, digestion, and fermentation
- 2023
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Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 413
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Tidskriftsartikel (refereegranskat)abstract
- The intake of dietary fibers is related with important benefits for human health. We produced two different arabinoxylan fibers with (FAX) and without ferulic acid linked (AX), 12.5 and 0.1 mg g−1 of ferulic acid respectively, by subcritical water extraction of wheat bran. Both FAX and AX fibers were used as supplement in bread production, while non-supplemented bread was used as control. Through an enzymatic deconstruction process we investigated the effect of bread making on the fibers, the preservation of their molecular structure (A/X ratio of 0.13 and Mw of 105 Da) and the interaction with other macromolecules in the bread. By mimicking the upper track digestion, we could confirm the non-digestability of the fibers and we used them for the fermentation with B. ovatus and B. adolescentis. The presence of AX fibers during fermentation showed specific substrate adaptation by the probiotic bacteria in correlation with its potential prebiotic effect.
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