| 1. |
- 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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| 2. |
- 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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| 3. |
- Palasingh, Chonnipa, 1992, et al.
(författare)
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Modification of xylan via an oxidation–reduction reaction
- 2022
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 292
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Argyri, Smaragda Maria, 1994, et al.
(författare)
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Contact-free measurement of surface tension on single droplet using machine learning and acoustic levitation
- 2023
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 640, s. 637-646
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis Acoustic levitation provides the possibility to deform levitated droplets in a controllable, and quantifiable manner, thus offering a means to measure the surface tension of a liquid droplet based on its deviation from sphericity. However, for new generation of multi-source and highly stable acoustic levitators, no model relates the acoustic pressure field to the deformation and surface tension. Utilizing a machine learning algorithm is expected to identify correlations between the experimental data without any set preconditions. Experiments A series of aqueous surfactant solutions with a large range of surface tensions were prepared, and evaporated under levitation, while the acoustic pressure was varied. A dataset of over 50,000 images was used for the training and evaluation of the machine learning algorithm. Prior to that, the machine learning approach was validated on in silico data that also included artificial noise. Findings We achieved high accuracy in predicting the surface tension of single standing droplets (±0.88 mN/m), and we surpassed certain physical conditions related to the size, and shape of the suspended samples that simpler theoretical models are subject to.
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| 5. |
- Argyri, Smaragda Maria, 1994, et al.
(författare)
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Customized and high-performing acoustic levitators for contact-free experiments
- 2024
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Ingår i: Journal of Science: Advanced Materials and Devices. - 2468-2284 .- 2468-2179. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Acoustic levitators are becoming an increasingly common research instrumentation for contact-free, lab-in-a-droplet studies. Recently, levitators that employ multiple, small, ultrasonic transducers have gained popularity, given their low price, temperature and spatial stability, low voltage, and accessibility. Yet, the current state-of-the-art device, TinyLev, presents limitations for certain applications in terms of stability, strength, and compactness. Herein, we developed three new levitators and evaluated the effect of the construction parameters (e.g., distance of opposing arrays, number and arrangement of transducers, etc.) on their performance. Compared to TinyLev, the best performing levitator from this work had half the number of transducers while presenting 1.7 and 3.5 times higher levitation capacity along the horizontal and vertical configurations, respectively, while the horizontal and vertical stability of a levitated object was improved 4.7 and 2.0 times, respectively. Additionally, we present a direct means to evaluate the acoustic radiation net force acting on a deformable object for uniaxial levitators, without the use of a microphone or a schlieren deflectometer for this type of levitators. The theoretical and experimental observations provide insights for adapting the acoustic levitator design for specific applications. Finally, we developed an open-source software which allows the evaluation of the acoustic pressure field generated by customized designs and provides the necessary files for 3D printing the scaffold of the levitator. This study aims to increase accessibility and promote further developments in contact-free experiments.
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| 6. |
- 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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| 7. |
- Eriksson, Viktor, 1995, et al.
(författare)
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A unified thermodynamic and kinetic approach for prediction of microcapsule morphologies
- 2024
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Ingår i: Journal of Colloid and Interface Science. - 1095-7103 .- 0021-9797. ; 662, s. 572-582
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: Microcapsule formation, following internal phase separation by solvent evaporation, is controlled by two main factors of thermodynamic and kinetic origin. Morphology prediction has previously focused on the final thermodynamical state in terms of spreading conditions, limiting the prediction accuracy. By additionally considering kinetic effects as the emulsion droplet evolves through the two-phase region of its ternary phase diagram during solvent evaporation, this should enhance prediction accuracy and explain a wider range of morphologies. Experiments: Dynamical interfacial tensions, and thereby spreading coefficients, during the formation of poly(methyl methacrylate) and poly(D,L-lactic-co-glycolic acid) microcapsules were measured by first establishing the boundaries and tie-lines of the ternary system in the emulsion droplets. Kinetic effects during the formation were investigated by varying the solvent evaporation rate and hence the time for polymer shell formation equilibration. The theory was validated by comparing predicted morphologies to microscopic snapshots of intermediate and final morphologies. Findings: The proposed theory explained both intermediate acorn and core–shell morphologies, where a late transition from acorn to core–shell produced microcapsules containing highly off-centered cores. By considering the kinetic factors, the formulation could be altered from yielding kinetically frozen acorns to core–shell and from yielding multicore to single core microcapsules.
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| 8. |
- Eriksson, Viktor, 1995, et al.
(författare)
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Microcapsule functionalization enables rate-determining release from cellulose nonwovens for long-term performance
- 2023
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Ingår i: Journal of Materials Chemistry B. - : Royal Society of Chemistry (RSC). - 2050-7518 .- 2050-750X. ; 11:12, s. 2693-2699
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Tidskriftsartikel (refereegranskat)abstract
- Functional textiles is a rapidly growing product segment in which sustained release of actives often plays a key role. Failure to sustain the release results in costs due to premature loss of functionality and resource inefficiency. Conventional application methods such as impregnation lead to an excessive and uncontrolled release, which - for biocidal actives - results in environmental pollution. In this study, microcapsules are presented as a means of extending the release from textile materials. The hydrophobic model substance pyrene is encapsulated in poly(d,l-lactide-co-glycolide) microcapsules which subsequently are loaded into cellulose nonwovens using a solution blowing technique. The release of encapsulated pyrene is compared to that of two conventional functionalization methods: surface and bulk impregnation. The apparent diffusion coefficient is 100 times lower for encapsulated pyrene compared to impregnated pyrene. This clearly demonstrates the rate-limiting barrier properties added by the microcapsules, extending the potential functionality from hours to weeks.
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| 9. |
- Eriksson, Viktor, 1995, et al.
(författare)
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Polyanhydride Microcapsules Exhibiting a Sharp pH Transition at Physiological Conditions for Instantaneous Triggered Release
- 2023
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Ingår i: Langmuir. - : American Chemical Society. - 0743-7463 .- 1520-5827. ; 39:49, s. 18003-18010
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Tidskriftsartikel (refereegranskat)abstract
- Stimulus-responsive microcapsules pose an opportunity to achieve controlled release of the entire load instantaneously upon exposure to an external stimulus. Core-shell microcapsules based on the polyanhydride poly(bis(2-carboxyphenyl)adipate) as a shell were formulated in this work to encapsulate the model active substance pyrene and enable a pH-controlled triggered release. A remarkably narrow triggering pH interval was found where a change in pH from 6.4 to 6.9 allowed for release of the entire core content within seconds. The degradation kinetics of the shell were measured by both spectrophotometric detection of degradation products and mass changes by quartz crystal microbalance with dissipation monitoring and were found to correlate excellently with diffusion coefficients fitted to release measurements at varying pH values. The microcapsules presented in this work allow for an almost instantaneous triggered release even under mild conditions, thanks to the designed core-shell morphology.
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| 10. |
- Fameau, Anne Laure, et al.
(författare)
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Liquid foams as sensors for the detection of biomarkers
- 2023
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Ingår i: Journal of Colloid and Interface Science. - 1095-7103 .- 0021-9797. ; 651, s. 987-991
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Tidskriftsartikel (refereegranskat)abstract
- Bioassays are widely used in healthcare to detect and quantify biomarkers, such as molecules or enzymes, which are crucial in monitoring diseases and health conditions. In developed countries, healthcare professionals use specialized reagents and equipment's to perform these bioassays. However, in less-industrialized countries, the creation of low cost, fast, and technically simple bioassays is required. Herein, we propose a simple approach for detecting biochemical markers using host–guest complexes containing a surfactant. When the biochemical marker is present, the host–guest complex is disrupted, releasing the surfactant and producing foam. The read-out mechanism relies on the change of foam volume as function of biomarker concentration. This change is quantifiable by the naked eye and can be measured with a simple ruler. We claim that the use of foams as sensing tool is an attractive, inexpensive, fast, and easy to handle on-site detection method.
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| 11. |
- 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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| 12. |
- 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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| 13. |
- 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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| 14. |
- 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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| 15. |
- 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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| 16. |
- 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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| 17. |
- 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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| 18. |
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| 19. |
- Svenningsson, Leo, 1990, et al.
(författare)
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Disassociated molecular orientation distributions of a composite cellulose–lignin carbon fiber precursor : A study by rotor synchronized NMR spectroscopy and X-ray scattering
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier Ltd. - 0144-8617 .- 1879-1344. ; 254
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose–lignin composite carbon fibers have shown to be a potential environmentally benign alternative to the traditional polyacrylonitrile precursor. With the associated cost reduction, cellulose–lignin carbon fibers are an attractive light-weight material for, e.g. wind power and automobile manufacturing. The carbon fiber tenacity, tensile modulus and creep resistance is in part determined by the carbon content and the molecular orientation distribution of the precursor. This work disassociates the molecular orientation of different components in cellulose–lignin composite fibers using rotor-synchronized solid-state nuclear magnetic resonance spectroscopy and X-ray scattering. Our results show that lignin is completely disordered, in a mechanically stretched cellulose–lignin composite fiber, while the cellulose is ordered. In contrast, the native spruce wood raw material displays both oriented lignin and cellulose. The current processes for fabricating a cellulose–lignin composite fiber cannot regain the oriented lignin as observed from the native wood. © 2020 The Author(s)
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| 20. |
- Svenningsson, Leo, 1990, et al.
(författare)
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Polarized Raman Spectroscopy Strategy for Molecular Orientation of Polymeric Fibers with Raman Tensors Deviating from the Molecular Frame
- 2020
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Ingår i: ACS Applied Polymer Materials. - : American Chemical Society (ACS). - 2637-6105. ; 2:11, s. 4809-4813
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Tidskriftsartikel (refereegranskat)abstract
- Polarized light is frequently used to identify molecular anisotropy in polymers, biological systems, and other materials. The influence of the Raman tensor by polarized light reveals not only the chemical structure but also information on the morphology of polymers. The orientation distribution of molecules in polymers has previously been determined for systems with the principal axis components of the Raman tensor parallel to the molecular frame. In many cases, the Raman tensor principal axis is not parallel to the molecular chain axis. Therefore, the orientation of the Raman tensor, relative to the molecular chain axis, is crucial if accurate information about the molecular orientation distribution is sought for. This work presents a strategy for separating the Raman tensor orientation angles from the molecular orientation angles for polymeric samples with fiber symmetry. Composite polymeric materials often experience signal overlap in the X-ray scattering wide-angle region, where the anisotropy is often resolved. While X-ray scattering investigates intermolecular distances, Raman spectroscopy resolves chemical information, and anisotropy, by the influence of Raman scattering. The quantitative principles presented here may aid in the evaluation of anisotropy in such composite materials.
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| 21. |
- Ulmefors, Hanna, et al.
(författare)
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Solution-Spinning of a Collection of Micro- and Nanocarrier-Functionalized Polysaccharide Fibers
- 2022
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Ingår i: Macromolecular materials and engineering. - : John Wiley and Sons Inc. - 1438-7492 .- 1439-2054. ; 307:8
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Tidskriftsartikel (refereegranskat)abstract
- Continuous polysaccharide fibers and nonwovens—based on cellulose, hydroxypropyl cellulose, chitosan, or alginate—containing biopolymeric microcapsules (MC) or mesoporous silica nanoparticles (MSN) are prepared using a wet-spinning or solution blowing technique. The MCs are homogeneously distributed in the fiber matrices whereas the MSNs form discrete micron-sized aggregates as demonstrated using scanning electron-, fluorescence-, and confocal microscopy. By encapsulating the model compound pyrene, it is shown that 95% of the substance remains in the fiber during the formation process as compared to only 7% for the nonencapsulated substance. The material comprising the MC has a strong impact on the release behavior of the encapsulated pyrene as investigated using methanol extraction. MCs based on poly(l-lactic acid) prove to be practically impermeable with no pyrene released in contrast to MCs based on poly(lactic-co-glycolic acid) which allow for diffusion of pyrene through the MC and fiber as visualized using fluorescence microscopy. © 2022 The Authors.
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| 22. |
- Vavra, Szilvia, 1990, et al.
(författare)
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Transport Properties and Local Structure of an Imidazole/Protic Ionic Liquid Mixture Confined in the Mesopores of Hydrophobic Silica
- 2021
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:4, s. 2607-2618
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Tidskriftsartikel (refereegranskat)abstract
- The local structure and the molecular dynamics of an imidazole/protic ionic liquid mixture have been investigated while confined in only ca. 5 nm mesopores of silica particles. The walls of the silica pores were functionalized with trioctyl groups to ensure a hydrophobic character, and a series of hybrid materials with varying liquid-to-silica ratios were investigated. Results from vibrational spectroscopy (both Raman and infrared) indicate that the local ion-ion interactions as well as the nature of hydrogen bonds inside the nanopores are not significantly different from the case of the bulk liquid mixture. Nevertheless, the ionic conductivity decreases rapidly and monotonically with decreasing amount of liquid, while the self-diffusion coefficients measured by pulsed field gradient nuclear magnetic resonance (NMR) show a distinct dependence on composition. The population of molecules outside the particles seems to contribute with an enhanced diffusivity, while the molecules inside the mesopores diffuse at a rate comparable to that observed in the bulk liquid. In addition, when experimentally possible, we have measured higher diffusivities for the exchangeable -NH proton than for any other molecular species, which is indicative of a decoupled proton motion. Results from X-ray scattering, employed to elucidate the local molecular structure, reveal an additional feature characteristic of the nanoconfined state, which is associated with a real space distance of about 3.5 nm. This distance describes a specific molecular organization inside the mesopores and may reflect the formation of a monolayer of the octyl-imidazolium cations self-assembled at the hydrophobic silica surface. Such a local structure would favor the localization of charges, including the exchangeable protons. In addition, the analysis of molar conductivity suggests that a major problem with a low pore filling is the emergence of discontinuities throughout the liquid phase.
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| 23. |
- Wiberg, Cedrik, 1989, et al.
(författare)
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Naphthalene diimides (NDI) in highly stable pH-neutral aqueous organic redox flow batteries
- 2021
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 896
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Tidskriftsartikel (refereegranskat)abstract
- In the pursuit of environmentally friendly energy storage, aqueous organic redox flow batteries (AORFBs) that use naphthalene diimide hold promise for successful application. In the present article, two different naphthalene diimides (NDI) are studied as negative electrolyte materials for pH-neutral aqueous organic/ organometallic redox flow batteries. The two molecules, one core-unsubstituted NDI (2H-NDI) and one coredimethylamino substituted NDI (2DMA-NDI) are coupled with a solubilized ferrocene (BTMAP-Fc) at a concentration of 50 mM in phosphate buffered potassium chloride. High energy efficiencies and coulombic efficiencies were obtained for both batteries, but a gradual capacity fade was observed while cycling. However, when changing the cation of the supporting electrolyte from potassium to ammonium, similar energy and coulombic efficiencies were obtained, but with undetectable capacity losses over 320 cycles. Finally, 2H-NDI and BTMAPFc at 500 mM were tested in the ammonium-based electrolyte, and while obtaining high coulombic efficiency, the energy efficiency and cycling stability decreased compared to the same system at lower concentration. It is concluded that loss of activity is mainly due to formation of electrochemically inactive compounds and that the electrolyte cation is of great importance for the outcome. Important design strategies for AORFB molecules include using supporting salts that prevent self-association and introducing sterically hindering substituents to the structures.
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| 24. |
- Wiberg, Cedrik, 1989, et al.
(författare)
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The electrochemical response of core-functionalized naphthalene Diimides (NDI) – a combined computational and experimental investigation
- 2021
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 367
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 Aqueous organic redox flow batteries (AORFBs) have attracted increased interest as sustainable energy storage devices due to the desire of increasing electricity production from renewable energy sources. Several organic systems have been tested as redox active systems in AORFBs but few fundamental electrochemical studies exist. This article provides reduction potentials and acid constants, pKa, of nine different core-substituted naphthalene diimides (NDI), calculated using density functional theory (DFT). Reduction potentials were acquired at each oxidation state for the nine species and were used to achieve a correlation between the electron donating ability of the substituents and the potential. Cyclic voltammograms were simulated using the scheme-of-squares framework to include both electron and proton transfer processes. The results show that the anion radical is unprotonated in the entire pH range, while the dianion can be protonated in one or two steps depending on the substituent. The core substituents may also have acid-base properties. and optimization of the redox properties for battery applications can therefore be obtained both by changing the core substituent and by changing pH of the electrolyte. Three core-substituted NDI molecules were studied experimentally and good qualitative agreement with the theoretically predicted behaviour was demonstrated. For 2,6-di(dimethylamino)-naphthalene diimide (2DMA-NDI), the calculations showed that one of the DMA substituents could be protonated in the accessible pH range and pKa was determined to 3.95 using 1H NMR spectroscopy. The redox mechanism of each molecule was explored and the qualitative agreement between theory and experiment clearly shows that this combination provides a better understanding of the systems and offers opportunities for further developments. The applicability of NDI for redox flow batteries is finally discussed.
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| 25. |
- Wu, Lulu
(författare)
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Development of Nanocellulose Materials for Nano-filtration and Microfluidic Cell Culture
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanocellulose, cellulose nanofibrils or nanocrystals, is an interesting material for a wide range of applications. It can be obtained from abundant sources (higher plants, bacteria and algae), and presents many advantages to be used in the biomedical field such as biological safety, high surface area, porosity, and tailorable rheological properties. This thesis selected two different areas to explore the use of nanocellulose materials in life sciences: bioprocessing of biological products and cell culture in microfluidic systems. The production of biopharmaceutical products (e.g. plasma-derived proteins) requires bioactive raw materials of animal or human origin, which present a viral risk. Virus contamination is one of the biggest challenges in the bioprocessing of such biological products, with size-exclusion virus filtration signalled as the preferred method. Commercial virus removal filters tend to have relatively low fluxes, which results in expensive industrial processes and the use of filters based on synthetic polymers is associated with environmental burden. When considering the application of microfluidic devices in cell research, the development of cheap and readily available nano- or micro-biomaterials that are easy to process and integrate is expected to advance the understanding of the relationship between cells and the microenvironment.The first part of the thesis focussed on Cladophora algae-derived cellulose nanofibrils virus removal filters (CCF-VFs) and investigated their application in the bioprocessing of plasma-derived proteins and stem cell differentiation medium. The second part explored the use of wood-derived cellulose nanofibrils (CNFs) as a cell culture substrate in microfluidics. Here, a concentric circular patterned CNF substrate was incorporated into a microfluidic chip to study the role of topography and shear stress in guiding the alignment of human umbilical vein endothelial cells (HUVECs). In conclusion, CCF-VFs show great potential to be integrated into the bioprocessing of plasma-derived products to remove viruses. The first evaluation of CCF-VFs in stem cell culture medium filtration showed promising results. Aligned CNFs were successfully integrated into microfluidic chips as a tool to study the role of mechanical cues on cell alignment.
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| 26. |
- 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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| 27. |
- 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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