| 1. |
- Arumughan, Vishnu, 1994, et al.
(författare)
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Anion-Specific Adsorption of Carboxymethyl Cellulose on Cellulose
- 2023
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 39:42, s. 15014-15021
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Tidskriftsartikel (refereegranskat)abstract
- Integration of fiber modification step with a modern pulp mill is a resource efficient way to produce functional fibers. Motivated by the need to integrate polymer adsorption with the current pulping system, anion-specific effects in carboxymethylcellulose (CMC) adsorption have been studied. The QCM-D adsorption experiments revealed that CMC adsorption to the cellulose model surface is prone to anion-specific effects. A correlation was observed between the adsorbed CMC and the degree of hydration of the co-ions present in the magnesium salts. The presence of a chaotropic co-ion such as nitrate increased the adsorption of CMC on cellulose compared to the presence of the kosmotropic sulfate co-ion. However, anion-specificity was not significant in the case of salts containing zinc cations. The hydration of anions determines the distribution of the ions at the interface. Chaotropic ions, such as nitrates, are likely to be distributed near the chaotropic cellulose surface, causing changes in the ordering of water molecules and resulting in greater entropy gain once released from the surface, thus increasing CMC adsorption.
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| 2. |
- Elf, Patric, et al.
(författare)
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Molecular Dynamics Simulations of Cellulose and Dialcohol Cellulose under Dry and Moist Conditions
- 2023
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 24:6, s. 2706-2720
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Tidskriftsartikel (refereegranskat)abstract
- The development of wood-based thermoplastic polymers that can replace synthetic plastics is of high environmental importance, and previous studies have indicated that cellulose-rich fiber containing dialcohol cellulose (ring-opened cellulose) is a very promising candidate material. In this study, molecular dynamics simulations, complemented with experiments, were used to investigate how and why the degree of ring opening influences the properties of dialcohol cellulose, and how temperature and presence of water affect the material properties. Mechanical tensile properties, diffusion/mobility-related properties, densities, glass-transition temperatures, potential energies, hydrogen bonds, and free volumes were simulated for amorphous cellulosic materials with 0-100% ring opening, at ambient and high (150 °C) temperatures, with and without water. The simulations showed that the impact of ring openings, with respect to providing molecular mobility, was higher at high temperatures. This was also observed experimentally. Hence, the ring opening had the strongest beneficial effect on “processability” (reduced stiffness and strength) above the glass-transition temperature and in wet conditions. It also had the effect of lowering the glass-transition temperature. The results here showed that molecular dynamics is a valuable tool in the development of wood-based materials with optimal thermoplastic properties.
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| 3. |
- Kainulainen, Tuomo P., et al.
(författare)
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Utilizing Furfural-Based Bifuran Diester as Monomer and Comonomer for High-Performance Bioplastics: Properties of Poly(butylene furanoate), Poly(butylene bifuranoate), and Their Copolyesters
- 2020
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 21, s. 743-752
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Tidskriftsartikel (refereegranskat)abstract
- Two homopolyesters and a series of novel random copolyesters were synthesized from two bio-based diacid esters, dimethyl 2,5-furandicarboxylate, a well-known renewable monomer, and dimethyl 2,2′-bifuran-5,5′-dicarboxylate, a more uncommon diacid based on biochemical furfural. Compared to homopolyesters poly(butylene furanoate) (PBF) and poly(butylene bifuranoate) (PBBf), their random copolyesters differed dramatically in that their melting temperatures were either lowered significantly or they showed no crystallinity at all. However, the thermal stabilities of the homopolyesters and the copolyesters were comparable. Based on tensile tests from amorphous film specimens, it was concluded that the elastic moduli, tensile strengths, and elongation at break values for all copolyesters were similar as well, irrespective of the furan:bifuran molar ratio. Tensile moduli of approximately 2 GPa and tensile strengths up to 66 MPa were observed for amorphous film specimens prepared from the copolyesters. However, copolymerizing bifuran units into PBF allowed the glass transition temperature to be increased by increasing the amount of bifuran units. Besides enhancing the glass transition temperatures, the bifuran units also conferred the copolyesters with significant UV absorbance. This combined with the highly amorphous nature of the copolyesters allowed them to be melt-pressed into highly transparent films with very low ultraviolet light transmission. It was also found that furan–bifuran copolyesters could be as effective, or better, oxygen barrier materials as neat PBF or PBBf, which themselves were found superior to common barrier polyesters such as PET.
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| 4. |
- Nilsson, K., et al.
(författare)
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Physiochemical and thermal characterisation of faba bean starch
- 2022
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Ingår i: Journal of Food Measurement and Characterization. - : Springer Nature. - 2193-4126 .- 2193-4134. ; 16:6, s. 4470-4485
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Tidskriftsartikel (refereegranskat)abstract
- The structure and physicochemical properties of starch isolated from the cotyledon and hull of faba beans and from wheat (as reference) were examined using 16 different methods. The amylose content in faba bean cotyledon and hull starch was 32% and 36%, respectively, and that in wheat starch was 21%. The faba bean cotyledon and hull starch were structurally alike both displaying C-polymorphic pattern, a similar degree of branching and similar branch chain length distributions. Wheat starch had a significantly greater prevalence of short amylopectin chains (DP < 12) and a higher degree of branching. Granules in both faba bean starches exhibited surface cracks and were more homogenous in size than the smoother wheat starch granules. Gelatinisation temperature was higher for the faba bean starches, likely as an effect of high amylose content and longer starch chains delaying granular swelling. Cotyledon starch produced pastes with the highest viscosities in all rheological measurements, probably owing to larger granules. Higher prevalence of lipids and resistant starch reduced the viscosity values for hull starch. For all starches, viscosity increased at faster heating rates. During the rheological analyses, the samples were exposed to different instruments, heating rates and temperatures ranges, differing from standard rheological procedures, which could help predict how different processing techniques effect the final starch textures.
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| 5. |
- Nilsson, Robin, 1993, et al.
(författare)
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Experimental and simulated distribution and interaction of water in cellulose esters with alkyl chain substitutions
- 2023
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 306
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the effect of the average length of substituted side chains in different cellulose esters on water sorption and the water association mechanism. For this purpose, a set of esters with a similar total degree of substitution was selected: cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Dynamic vapor sorption was used to determine the effect of the side chain length on sorption, desorption, and the occurrence of water clustering. Since water association in the structure was of interest, molecular dynamics simulations were performed on cellulose acetate and cellulose acetate propionate. This study showed that cellulose acetate appears to be water-sensitive and experiences hysteresis upon water sorption, which was attributed to structural changes. The simulations also showed that water is screened out by the side chains and forms intermolecular hydrogen bonds, primarily to the carbonyl oxygen rather than the residual hydroxyl groups.
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| 6. |
- Sivan, Pramod, 1984-, et al.
(författare)
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Sequential extraction of hemicelluloses by subcritical water improves saccharification of hybrid aspen wood grown in greenhouse and field conditions
- 2023
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Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 25:14, s. 5634-5646
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Tidskriftsartikel (refereegranskat)abstract
- Fast growing hardwoods are one of the major renewable resources available to produce bio-based materials, platform chemicals and biofuels. However, the industrial processing of lignocellulosic biomass is hindered by the complex molecular structure of the cell wall components and their supramolecular organization. This highlights the necessity of improving green processing strategies to enhance biomass conversion to valuable products from industrial wood production species. In the present study, we implemented a hydrothermal step by sequential subcritical water (SW) in aspen wood prior to saccharification and validated the process for trees grown in greenhouse and field conditions. Subcritical water enables extraction of non-cellulosic cell wall polysaccharides in native polymeric form. A major part of the pectic fraction was easily extracted within the first 10 min, while acetylated xylan was enriched in the subsequent extracts after 20- and 30-min rounds. Prolonged extraction (above 60 min) resulted in partial deacetylation and a reduction of the molar mass of xylan. The analysis of the residues enriched with cellulose and lignin showed several micromorphological changes caused by subcritical water treatment, such as an increased porosity, a loosening of the fibre matrix and a decrease in the macrofibrillar dimensions. These morphological and molecular changes in the organization of cell wall polymers after SW treatment significantly enhanced saccharification yields compared to those of non-treated aspen wood chips from both field and greenhouse conditions. Our study demonstrates that SW can be implemented as pretreatment prior to saccharification reducing the requirements for chemical acid pretreatments. This process enables the extraction of native non-cellulosic cell wall polymers for potential material applications and promotes the subsequent biochemical conversion of the residual biomass into fermentable sugars and platform chemicals in future biorefineries.
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| 7. |
- Özeren, Hüsamettin Deniz
(författare)
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Plasticization of Biobased Polymers: A Combined Experimental and Simulation Approach
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The field of bio-based plastics has developed significantly in recent decades and there is an increasing demand for industries to shift from petrochemical to biobased polymers. Biobased polymers offer competitive properties, and in many cases have advantages in terms of cost. Thermoplastic starch is already commercially available, while wheat-gluten protein-based materials are considered to be promising candidates for commercial use.Biobased materials can, however, have several drawbacks that have to be handled. Starch-based materials are, in general, brittle due to the stiff glucose-based molecular chain and hydrogen bond network. This is the case also for proteins (due to the stiff peptide bond, bulky side groups and hydrogen bond network), like for example gluten. These issues can, however, be resolved with effective compatible plasticizers. But in order to be able to optimize the choice of the right plasticizer for a specific polymer, there is a need for an increased understanding of the plasticizer mechanisms. Besides, a methodology for prediction of the plasticizer amount needed, as well as to be able to rank possible plasticizer candidates, based on their effectiveness. As a part of the development of a methodology (based on the combination of experimental and molecular-dynamics simulations) for prediction of plasticization and to investigate and understand plasticizer mechanisms, the main material investigated was starch, but also wheat gluten, both plasticized with glycerol. The main plasticizer used to date for biobased polymer materials is glycerol, because of its effectiveness, stability and low cost. In addition, it is also a large byproduct of biodiesel production. A number of other plasticizer candidates were also studied for the starch system to see if the developed methodology could be used to rank plasticizers. Diols were tested in the starch system as plasticizers, but they had no or little plasticization effect. Nevertheless, they gave rise to unexpected structures and properties. Several techniques were used to determine the experimental properties of the bio-based films, including calorimetry, gravimetry, dynamic mechanical analysis, and tensile testing.The results (based on mechanical and thermal properties) showed that the methodology could be used to rank plasticizers in terms of their effectiveness. It was also possible to predict the amount of plasticizer needed for effective softening. With the help of the simulations, the emollient effect could be studied in detail and largely explained by hydrogen bonding effects. The methodology was also developed to be able to predict from simulation not only trends in mechanical properties but also absolute values in stiffness and strength at elongation rates corresponding to experimental measurements.
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| 8. |
- Özeren, Hüsamettin Deniz, et al.
(författare)
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Prediction of Plasticization in a Real Biopolymer System (Starch) using Molecular Dynamics Simulations
- 2020
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 187:108387
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Tidskriftsartikel (refereegranskat)abstract
- Virgin biopolymers are often brittle, which means that they need efficient, sustainable, non-toxic plasticizers for most practical applications. Although the mechanical properties of biopolymers plasticized with e.g. sugars have been extensively investigated, the explanation why efficient plasticization normally only occurs above 20 wt% plasticizer is still lacking. In this work, starch/glycerol was used as a model system to show that all-atom molecular dynamics (MD) simulations can be used to capture the transition region at 20–30 wt% plasticizer, where plasticization becomes pronounced. Tensile properties and PVT data (densities and glass transition temperatures) were obtained both from MD simulations and from measurements on real starch/glycerol materials, confirming that MD could capture the experimentally observed transition region. Also, the simulated glycerol diffusivity correlated well with the trends in the mechanical properties. Percolation theory was used to derive a probable explanation of the observed transition. The results indicate that the MD methodology can be used also for other polymer/plasticizer systems and has the potential to be a valuable tool for optimizing the type and amount of plasticizer in a given polymer, as well as being a tool for the design of new efficient plasticizers.
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| 9. |
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| 10. |
- Özeren, Hüsamettin Deniz
(författare)
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Prediction of Real Tensile Properties using Extrapolations from Atomistic Simulations: An Assessment on Thermoplastic Starch
- 2021
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 228:123919
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Tidskriftsartikel (refereegranskat)abstract
- Atomistic molecular dynamics (MD) simulations can be used to predict mechanical properties, such as stiffness and strength, for polymers. A concern is unavoidably high strain rates in simulations compared with those in physical experiments. To quantitatively capture the mechanical properties of the ‘real’ material, i.e., to predict absolute values rather than just qualitative trends, extrapolation to realistic strain rates is required. In this study, different strain-rate extrapolation strategies involving time-temperature shifting with the Williams-Landel-Ferry equation (above Tg) and the Eyring equation (below Tg) were evaluated, using thermoplastic starch as an example. MD simulations were first used to compute the stiffness and strength at three (high) strain rates over a wide range of temperatures. The mechanical MD data were then horizontally time-temperature shifted, resulting in master curves with strain-rate (x-axis) versus mechanical properties (y-axis). The precision in the prediction of experimental data was quite good in several cases, but was dependent on the extrapolation method and the specific thermoplastic starch system. A notable finding was that the simulations could be simplified using fewer simulation strain rates and temperatures. The extrapolation techniques used here are expected to be valid for other polymer systems, but this remains to be validated.
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