| 1. |
- Benselfelt, Tobias, 1989-
(författare)
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Design of Cellulose-based Materials by Supramolecular Assemblies
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Due to climate change and plastic pollution, there is an increasing demand for bio-based materials with similar properties to those of common plastics yet biodegradable. In this respect, cellulose is a strong candidate that is already being refined on a large industrial scale, but the properties differ significantly from those of common plastics in terms of shapeability and water-resilience.This thesis investigates how supramolecular interactions can be used to tailor the properties of cellulose-based materials by modifying cellulose surfaces or control the assembly of cellulose nanofibrils (CNFs). Most of the work is a fundamental study on interactions in aqueous environments, but some material concepts are presented and potential applications are discussed.The first part deals with the modification of cellulose by the spontaneous adsorption of xyloglucan or polyelectrolytes. The results indicate that xyloglucan adsorbs to cellulose due to the increased entropy of water released from the surfaces, which is similar to the increased entropy of released counter-ions that drives polyelectrolyte adsorption. The polyelectrolyte adsorption depends on the charge of the cellulose up to a limit after which the charge density affects only the first adsorbed layer in a multilayer formation.Latex nanoparticles with polyelectrolyte coronas can be adsorbed onto cellulose in order to prepare hydrophobic cellulose surfaces with strong and ductile wet adhesion, provided the glass transition of the core is below the ambient temperature.The second part of the thesis seeks to explain the interactions between different types of cellulose nanofibrils in the presence of different ions, using a model consisting of ion-ion correlation and specific ion effects, which can be employed to rationally design water-resilient and transparent nanocellulose films. The addition of small amounts of alginate also creates interpenetrating double networks, and these networks lead to a synergy which improves both the stiffness and the ductility of the films in water.A network model has been developed to understand these materials, with the aim to explain the properties of fibril networks, based on parameters such as the aspect ratio of the fibrils, the solidity of the network, and the ion-induced interactions that increase the friction between fibrils. With the help of this network model and the model for ion-induced interactions, we have created films with wet-strengths surpassing those of common plastics, or a ductility suitable for hygroplastic forming into water-resilient and biodegradable packages. Due to their transparency, water content, and the biocompatibility of cellulose, these materials are also suitable for biomaterial or bioelectronics applications.
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| 2. |
- Brooke, Robert, 1989-, et al.
(författare)
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Nanocellulose and PEDOT:PSS composites and their applications
- 2023
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Ingår i: Polymer Reviews. - : Taylor and Francis Ltd.. - 1558-3724 .- 1558-3716. ; :2, s. 437-
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Tidskriftsartikel (refereegranskat)abstract
- The need for achieving sustainable technologies has encouraged research on renewable and biodegradable materials for novel products that are clean, green, and environmentally friendly. Nanocellulose (NC) has many attractive properties such as high mechanical strength and flexibility, large specific surface area, in addition to possessing good wet stability and resistance to tough chemical environments. NC has also been shown to easily integrate with other materials to form composites. By combining it with conductive and electroactive materials, many of the advantageous properties of NC can be transferred to the resulting composites. Conductive polymers, in particular poly(3,4-ethylenedioxythiophene:poly(styrene sulfonate) (PEDOT:PSS), have been successfully combined with cellulose derivatives where suspensions of NC particles and colloids of PEDOT:PSS are made to interact at a molecular level. Alternatively, different polymerization techniques have been used to coat the cellulose fibrils. When processed in liquid form, the resulting mixture can be used as a conductive ink. This review outlines the preparation of NC/PEDOT:PSS composites and their fabrication in the form of electronic nanopapers, filaments, and conductive aerogels. We also discuss the molecular interaction between NC and PEDOT:PSS and the factors that affect the bonding properties. Finally, we address their potential applications in energy storage and harvesting, sensors, actuators, and bioelectronics. © 2022 The Author(s).
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| 3. |
- Carrick, Christopher, et al.
(författare)
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Lightweight, Highly Compressible, Noncrystalline Cellulose Capsules
- 2014
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:26, s. 7635-7644
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate how to prepare extraordinarily deformable, gas-filled, spherical capsules from nonmodified cellulose. These capsules have a low nominal density, ranging from 7.6 to 14.2 kg/m(3), and can be deformed elastically to 70% deformation at 50% relative humidity. No compressive strain-at-break could be detected for these dry cellulose capsules, since they did not rupture even when compressed into a disk with pockets of highly compressed air. A quantitative constitutive model for the large deformation compression of these capsules is derived, including their high-frequency mechanical response and their low-frequency force relaxation, where the latter is governed by the gas barrier properties of the dry capsule. Mechanical testing corroborated these models with good accuracy. Force relaxation measurements at a constant compression rendered an estimate for the gas permeability of air through the capsule wall, calculated to 0.4 mL mu m/m(2) days kPa at 50% relative humidity. These properties taken together open up a large application area for the capsules, and they could most likely be used for applications in compressible, lightweight materials and also constitute excellent model materials for adsorption and adhesion studies.
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| 4. |
- Utsel, Simon, 1984-
(författare)
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Surface Modification of Cellulose-based Materials for Tailoring of Interfacial Interactions
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The awareness of our need for a sustainable society has encouraged the search for renewable, high quality materials that can replace oil-based products. This, in combination with increased competition in the forest industry, has stimulated a lot of research into different types of wood-based materials where cellulose-rich fibers are combined with different types of polymers. There is hence a great need to develop efficient fiber modification techniques by which the fibers can be tailored to obtain specific properties. A significant change in properties can be achieved by modifying only the surface of fibers although only a relatively small amount of the total fiber material is modified. In this thesis, several surface modification techniques are presented as new tools to design the properties of different cellulose-based materials.In paper I, thermoresponsive nanocomposites have been assembled from specially designed thermoresponsive block copolymers and nanofibrillated cellulose. The block copolymers have one thermoresponsive block and one cationically charged block which can thus attach the polymer to an oppositely charged fiber/fibril surface. Multilayers were assembled with these block copolymers and nanofibrillated cellulose (NFC) utilizing the Layer-by-Layer (LbL) technique, resulting in thin films with a thermoresponsive behavior.In papers II and III, amphiphilic block copolymers with one less polar high molecular weight block and one cationic block were synthesized for use as a compatibilizer between fibers/fibrils and less polar polymer matrices in composites. The less polar block consisted of polystyrene (PS) in paper II and poly(ɛ-caprolactone) (PCL) in paper III. These polymers self-assemble into cationic micelles in water which can adsorb to oppositely charged surfaces, such as cellulose-based fibers/fibrils, in water under mild conditions and decrease the surface energy of the surface. Atomic force microscopy (AFM) was used to evaluate the adhesive properties of surfaces treated with these compatibilizers which clearly showed the formation of physical entanglements across the interfaces, which are essential for improved interfacial adhesion in the final composites. This modification technique could probably be utilized to make fiber-based composites with better mechanical properties. To be able to better compare this physical modification technique with a more traditional covalent grafting-from approach a method to measure attached amounts of grafted PCL onto cellulose model surfaces was developed in paper IV using a quartz crystal microbalance (QCM).In paper V, multilayers of poly(allylamine hydrochloride) (PAH) and hyaluronic acid (HA) were assembled using the LbL technique and surface structure, build-up and adhesive behavior of the multilayers were evaluated. AFM force measurements showed that a significant adhesion even at long separation distances between two surfaces treated with PAH/HA multilayers could be achieved due to extensive interdiffusion across the interface during contact, leading to significant disentanglement during separation. Fundamental parameters contributing to improved adhesion for this type of system have been evaluated and this knowledge could be used to improve cellulose-based fiber networks and possibly also other types of cellulose-based materials.In paper VI, click chemistry was used to covalently attach dendrons to cellulose surfaces and further modify them with mannose groups to obtain specific interactions with Concanavalin A. The protein interactions were studied at different protein concentrations with a QCM. The multivalent dendronized surface showed a 10-fold increase in sensitivity to the protein compared to a monovalent reference surface demonstrating greatly improved interfacial interactions. This approach could be used to improve interactions at different types of interfaces.
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| 5. |
- Senf, Deborah, et al.
(författare)
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Tailormade Polysaccharides with Defined Branching Patterns: Enzymatic Polymerization of Arabinoxylan Oligosaccharides
- 2018
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 57:37, s. 11987-11992
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Tidskriftsartikel (refereegranskat)abstract
- The heterogeneous nature of non-cellulosic polysaccharides, such as arabinoxylan, makes it difficult to correlate molecular structure with macroscopic properties. To study the impact of specific structural features of the polysaccharides on crystallinity or affinity to other cell wall components, collections of polysaccharides with defined repeating units are required. Herein, a chemoenzymatic approach to artificial arabinoxylan polysaccharides with systematically altered branching patterns is described. The polysaccharides were obtained by glycosynthase-catalyzed polymerization of glycosyl fluorides derived from arabinoxylan oligosaccharides. X-ray diffraction and adsorption experiments on cellulosic surfaces revealed that the physicochemical properties of the synthetic polysaccharides strongly depend on the specific nature of their substitution patterns. The artificial polysaccharides allow structure–property relationship studies that are not accessible by other means.
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| 6. |
- Wang, Zhen, et al.
(författare)
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Copper-Plated Paper for High-Performance Lithium-Ion Batteries
- 2018
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Ingår i: Small. - : Wiley-VCH Verlagsgesellschaft. - 1613-6810 .- 1613-6829. ; 14:48
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Tidskriftsartikel (refereegranskat)abstract
- Paper is emerging as a promising flexible, high surface-area substrate for various new applications such as printed electronics, energy storage, and paper-based diagnostics. Many applications, however, require paper that reaches metallic conductivity levels, ideally at low cost. Here, an aqueous electroless copper-plating method is presented, which forms a conducting thin film of fused copper nanoparticles on the surface of the cellulose fibers. This paper can be used as a current collector for anodes of lithium-ion batteries. Owing to the porous structure and the large surface area of cellulose fibers, the copper-plated paper-based half-cell of the lithium-ion battery exhibits excellent rate performance and cycling stability, and even outperforms commercially available planar copper foil-based anode at ultra-high charge/discharge rates of 100 C and 200 C. This mechanically robust metallic-paper composite has promising applications as the current collector for light-weight, flexible, and foldable paper-based 3D Li-ion battery anodes.
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| 7. |
- Farahani, Saina Kishani, et al.
(författare)
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Experimental and Theoretical Evaluation of the Solubility/Insolubility of Spruce Xylan (Arabino Glucuronoxylan)
- 2019
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 20:3, s. 1263-1270
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 American Chemical Society. The molecular solubility of softwood arabinoglucuronoxylan (AGX) has been thoroughly investigated, and it has been shown that the chemical and physical structures of the extracted hemicellulose are not significantly influenced by different purification steps, but a transient molecular solubility of AGX was observed in aqueous media at low concentrations (1 g/L) when the dissolved macromolecules had a hydrodynamic diameter of up to 10 nm. A phase separation was detected when the concentration was increased to 15 g/L leading to an association of the smaller molecules into fractal structures with a considerably larger diameter, even though the dispersions were still transparent to ocular inspection. Dynamic Light Scattering and Cryo-Transmission Electron Microscopy showed dimensions in the range of 1000 nm. The phase separation of the sample was further characterized by estimating the χ-interaction parameter of AGX in water using the Flory-Huggins theory, and the results supported that water is a poor solvent for AGX. This behavior is crucial when films and hydrogels based on these biopolymers are made, since the association will dramatically affect barrier and mechanical properties of films made from these materials.
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| 8. |
- Namata, Faridah
(författare)
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Cationic Dendritic Polymers and Their Hybridization with Cellulose Nanofibrils
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Antimicrobial resistance (AMR) is one of the major global threats to thehealth of humans, animals, plants and ecosystems. AMR arises whenbacteria, viruses, fungi, and parasites undergo changes over time; makingmedicines such as antibiotics, antivirals, antifungals and antiparasiticineffective at treating infections. In 2014, it caused approximately 700 000deaths worldwide which increased to 1.27 million deaths in 2019.Consequently, there is a need to explore novel technologies andtreatments. Within the development of alternatives to conventional smallmoleculeantibiotics, polycationic macromolecules have emerged, such asdendritic polymers and their nanomaterials.Dendrimers are high precision, branched macromolecules with a highdensity of terminal functional groups. Their unique architecture and abilityfor precise control over both shape and surface functionality make themsuitable for biomedical applications such as drug delivery, gene deliveryand antimicrobials.Cellulose nanofibrils (CNFs) are nanoscale fibrils of cellulose, an abundantpolymer typically derived from wood. The prolonged reliance on fossilbasedproducts is associated with a wide range of adverse environmentalconsequences which have prompted the exploration of raw materialsderived from renewable resources. The intriguing properties of CNFs, suchas high elastic moduli and low densities, have made them attractive asstructural materials from sustainable sources that can form 3D networks.The combination of cationic dendritic polymers and cellulose nanofibrils isexplored in this thesis and presents an exciting avenue for the developmentof innovative biomaterials with antibacterial properties andbiocompatibility. Part of the work focuses on the synthesis of cationicdendritic polymers, with varying types of cationic groups at the peripheralthrough the use of fluoride-promoted esterification chemistry and thioleneclick reactions. Another part focuses on creating crosslinked hybridhydrogels using cationic dendrimers and anionic CNFs. Finally, a part ofthe thesis presents the preparation of hydrogels consisting of dendriticlinear-dendritic (DLD) polymer solutions and anionic CNFs. Overall, thefindings showcase the versatility and promise of the developed cationicdendritic polymers and CNF-based hydrogels against Escherichia coli,Pseudomonas aeruginosa and Staphylococcus aureus bacterial strainswhilst exhibiting low cytotoxicity.
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| 9. |
- Nordenström, Malin
(författare)
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Colloidal interactions and arrested dynamics of cellulose nanofibrils
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Over the past decades, concerns for the environment have increased and efforts to achieve a sustainable society have intensified. One particular challenge is to replace fossil-based plastics with biodegradable materials produced from renewable resources. Cellulose nanofibril (CNF)-based materials are strong candidates due to their excellent mechanical properties, nano-dimensions and molecular structure, which is suitable for modification. CNFs can be obtained from wood and are elongated, often charged, particles which are usually handled in aqueous dispersions. The colloidal stability is sensitive, and instability results in aggregation or transition to an arrested state. Since the properties of CNF-based materials rely on dispersion of the CNFs, an understanding of the colloidal behaviour is crucial.This work has focused on the interactions and dynamics of CNFs in different colloidal states. Arrested states of CNFs were studied in detail and it was found that two types of arrested state exist, with different colloidal interactions and mechanisms governing their formation. The dynamics in arrested and dispersed states were studied by tracer diffusion measurements, and it was found that small amounts of CNFs can constitute an excellent stabiliser for other particle dispersions according to a so far unexplored mechanism.The effects of altering the colloidal interactions using different strategies were also evaluated. The counterions of CNFs were exchanged and the impact on the swelling behaviour was measured. Based on the results, different contributions to the counterion-dependent interactions are discussed. Two strategies for using polymers to alter the interactions were furthermore studied. Polyethylene glycol (PEG) was grafted to CNFs in order to increase the arrested state threshold concentration. PEG, carboxymethyl cellulose and lignin, were also used as additives which improved the redispersion of dried CNF, especially in the case of samples containing lignin.
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| 10. |
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