| 1. |
- Huang, Xiao, 1987-
(författare)
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Conducting Redox Polymers for Electrode Materials : Synthetic Strategies and Electrochemical Properties
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organic electrode materials represent an intriguing alternative to their inorganic counterparts due to their sustainable and environmental-friendly properties. Their plastic character allows for the realization of light-weight, versatile and disposable devices for energy storage. Conducting redox polymers (CRPs) are one type of the organic electrode materials involved, which consist of a π-conjugated polymer backbone and covalently attached redox units, the so-called pendant. The polymer backbone can provide conductivity while it is oxidized or reduced (i. e., p- or n-doped) and the concurrent redox chemistry of the pendant provides charge capacity. The combination of these two components enables CRPs to provide both high charge capacity and high power capability. This dyad polymeric framework provides a solution to the two main problems associated with organic electrode materials based on small molecules: the dissolution of the active material in the electrolyte, and the sluggish charge transport within the material. This thesis introduces a general synthetic strategy to obtain the monomeric CRPs building blocks, followed by electrochemical polymerization to afford the active CRPs material. The choice of pendant and of polymer backbone depends on the potential match between these two components, i.e. the redox reaction of the pendant and the doping of backbone occurring within the same potential region. In the thesis, terephthalate and polythiophene were selected as the pendant and polymer backbone respectively, to get access to low potential CRPs. It was found that the presence of a non-conjugated linker between polymer backbone and pendant is essential for the polymerizability of the monomers as well as for the preservation of individual redox activities. The resulting CRPs exhibited fast charge transport within the polymer film and low activation barriers for charge propagation. These low potential CRPs were designed as the anode materials for energy storage applications. The combination of redox active pendant as charge carrier and a conductive polymer backbone reveals new insights into the requirements of organic matter based electrical energy storage materials.
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| 2. |
- Jämstorp Berg, Erik, 1980-
(författare)
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Diffusion Controlled Drug Release from Slurry Formed, Porous, Organic and Clay-derived Pellets
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Coronary artery disease and chronic pain are serious health issues that cause severe discomfort and suffering in society today. Antithrombotic agents and highly potent analgesics play a critical role in improving the recovery process for patients being treated for these diseases. This thesis focuses on the design and study of pellet-based drug dosage forms which allow diffusion-controlled delivery of drugs with the aim of achieving optimal therapeutic outcomes.A wet slurry process was used to mix the drug and the polymer and/or clay precursor excipients into a paste. The pellets were then shaped via ionotropic gelation (alginate hydrogel beads/pellets), extrusion/spheronization (halloysite clay pellets) or geopolymerization.The decrease in the drug diffusion rate in the alginate beads was affected by the drug's molecular size and charge and the characteristics (such as concentration and chemical structure) of the surrounding alginate gel.The halloysite clay pellets provided sustained release of the highly potent drug fentanyl at both gastric pH 1 and intestinal pH 6.8. As expected, crushing the pellets reduced the diffusion barrier, resulting in more rapid release (dose dumping).The use of mechanically strong geopolymer gels was investigated as a potential means of preventing dose dumping as a result of crushing of the dosage form. Variations in the synthesis composition resulted in drastic changes in the microstructure morphology, the porosity, the mechanical stability and the drug release rate. Pore network modeling and finite element simulations were employed to theoretically evaluate the effects of porosity and drug solubility in the geopolymer structure on the drug release process. Fitting the model parameters to experimental data showed that increased average pore connectivity, a greater pore size distribution, and increased drug solubility in the pellet resulted in an increased drug release rate. Furthermore, incorporation of pH-sensitive organic polymers in the geopolymer structure reduced the high drug release rate from the pellets at gastric pH. These results indicate that geopolymers have potential for use in pellet form; both the release rate of the drug and the mechanical stability of the pellets can be optimized to prevent dose dumping.
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| 3. |
- Nordström, Josefina, 1977-
(författare)
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Compression analysis as a tool for technical characterization and classification of pharmaceutical powders
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There are today strong incentives for an increased understanding of material properties and manufacturing processes to facilitate the development of new technologies in the pharmaceutical industry. The purpose of this thesis was to suggest methods requiring a low sample amount for characterization of technical properties of powders.Compression analysis was used to evaluate the formulation relevance of some compression equations. Using the mechanics of single granules to estimate powder functionality was part of this work. It was concluded that the formability of granular solids and the plasticity of single granules could be determined with compression analysis by using the Kawakita model for single components and binary mixtures of ductile granules.Further on, the fragmentation propensity of solid particles could be estimated from compression analysis by using the Shapiro equation, enabling indicators of both the fragmentation and the deformation propensity of particles to be derived in one single compression test.The interpretations of the compression parameters were only valid if the influence of particle rearrangement was negligible for the overall compression profile. An index indicating the extent of particle rearrangement was developed and a classification system of powders into groups dependent on the incidence of particle rearrangement was suggested as tools to enable rational interpretations of compression parameters.The application of compression analysis was demonstrated by investigating the relevance of the mechanics of granular solids for their tableting abilities. The plasticity of single gran-ules was suggested to influence both the rate of compactibility and the mode of deformation, and consequently the maximal tablet strength. The degree of granule bed deformation was shown to be a potential in line process indicator to describe the tableting forming ability.This thesis contributes to a scheme, suitable in formulation work and process control, to describe manufacturability of powders for an enhanced tablet formulation technology.
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| 4. |
- Atluri, Rambabu, 1981-
(författare)
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Novel Syntheses, Structures and Functions of Mesoporous Silica Materials
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The field of mesoporous silica has been studied for about 20 years but it is still an area attracting a lot of attention. The use of novel templating molecules and several issues related to the synthesis and fine structural details are still poorly understood. These aspects are of special relevance to the theme of this thesis, which includes novel work on three fronts; the synthesis, characterization and applications of mesoporous materials. The work described in this thesis aims to contribute to the mesoporous field by developing novel methods of mesoporous silica synthesis without relying on surfactant micelles as the templating agent but focusing instead on the stacking arrangement of aromatic molecules such as folic acid. The novel route presented here leads to 2D hexagonal structures with p6mm symmetry possessing high mesoporosity and large surface areas. The versatility of this route at various synthesis temperatures and using hydrothermal treatments has also been investigated. A novel strategy is also proposed for the synthesis of mesocaged materials with Pm3n symmetry structures. The mechanism relies on the penetration of the neutral propylamino moiety of a co-structure directing agent into the hydrophobic core of the surfactant micelles. Beside these novel pathways, the effect of hydrothermal treatment (HT) at 100 oC on the 3D cubic Ia3d structure (AMS-6) over a long period of time was also examined, and the results show a phase transformation from a 3D cubic Ia3d to a 2D hexagonal p6mm structure and a return to the 3D cubic Ia3d structure at a later stage in the synthesis. This unexpected result is discussed. In this work, the detailed structural characterization of mesoporous materials using electron microscopy techniques is an important task. In particular, to extend previous knowledge, the fine structural details of mesocaged materials possessing Pm3n symmetry prepared with various amphiphilic surfactants under acidic and alkaline conditions has been investigated using electron crystallography and sorption studies. The results show subtle fine structural differences with materials prepared under alkaline conditions exhibiting the largest mesocage sizes. The cage and window sizes are primarily determined by the charge density of the surfactant and the thickness of the hydration layer surrounding the surfactant micelles. The relationship between the mesoporous structure and its function has been investigated by evaluating the rate of release of amphiphilic molecules, used as model molecules, from the internal pore structures of mesoporous materials with different pore geometries. In a similar study, the rate of proton diffusion from a liquid surrounding the mesoporous nanoparticles into the pore system of AMS-n was also assessed. The results show that the diffusion coefficients for the proton absorption process are higher than those for the release of the surfactant template molecules, with more complex 3D mesocaged particles showing the highest diffusion coefficients in both cases. Finally, the quantity of CO2 adsorption was measured by modifying the internal surfaces of mesocaged material with n-propylamino groups. Results show that the cage-connecting window sizes limit the surface coverage of n-propylamino groups by pore blocking and affect the volume of CO2 adsorption. In addition, at the molecular level, CO2 adsorption shows physisorption or chemisorption depending on the localized distribution of n-propylamino groups, as studied by in-situ infrared spectroscopy.
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| 5. |
- Blom, Tobias
(författare)
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Fabrication and Applications of a Focused Ion Beam Based Nanocontact Platform for Electrical Characterization of Molecules and Particles
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of new materials with novel properties plays an important role in improving our lives and welfare. Research in Nanotechnology can provide e.g. cheaper and smarter materials in applications such as energy storage and sensors. In order for this development to proceed, we need to be able to characterize the material properties at the nano-, and even the atomic scale. The ultimate goal is to be able to tailor them according to our needs. One of the great challenges concerning the characterization of nano-sized objects is how to achieve the physical contact to them. This thesis is focused on the contacting of nanoobjects with the aim of electrically characterizing them and subsequently understanding their electrical properties. The analyzed nanoobjects are carbon nanosheets, nanotetrapods, nanoparticles and molecular systems. Two contacting strategies were employed in this thesis. The first strategy involved the development of a focused ion beam (FIB) based nanocontact platform. The platform consists of gold nanoelectrodes, having nanogaps of 10-30 nm, on top of an insulating substrate. Gold nanoparticles, double-stranded DNA and cadmium telluride nanotetrapods have been trapped in the gaps by using dielectrophoresis. In certain studies, the gold electrodes have also been coated with conducting or non-conducting molecules, prior to the trapping of gold nanoparticles, in order to form molecular junctions. These junctions were subsequently electrically characterized to evaluate the conduction properties of these molecular systems. For the purpose of better controlling the attachment of molecules to the nanoelectrodes, a novel route to synthesize alkanedithiol coated gold nanoparticles was developed. The second contacting strategy was based on the versatility of the FIB instrument as a platform for in-situ manipulation and electrical characterization of non-functionalized and functionalized carbon nanosheets, where it was found that the functionalized samples had an increased conductivity by more than one order of magnitude. Both contacting strategies proved to be valuable for building knowledge around contacting and electrical characterization of nanoobjects
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| 6. |
- Pan, Ruijun
(författare)
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Cladophora Cellulose-based Separators for Lithium Batteries
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of lithium-ion batteries (LIBs) has been focused on exploring and improving the electrode materials and electrolytes in the past decades. An indispensable component, the separator, is however not studied as extensively. In general, a separator has two functions, i.e. preventing the direct contact between the cathode and anode and providing the ionic transport pathways. Commercial separators for LIBs are usually made of polyolefin materials, which often have low thermal stabilities and poor electrolyte wettabilities.In this thesis, a new type of material, i.e. Cladophora cellulose, is used to manufacture separators for LIBs and lithium-metal batteries (LMBs). The separators, made with Cladophora cellulose fibers via a straightforward paper making method, possess several advantages compared to conventional polyolefin separators regarding, e.g. ionic conductivity, thermal stability, electrolyte wettability and pore distribution, providing promising alternatives for battery separators.Apart from studying the two basic functions mentioned above, two types of advanced separator functionalities have been studied, i.e. redox-activity and the attainment of a homogeneous current distribution, in conjunction with proposals for new separator designs.Two types of redox-active separators have been devised for the first time in the separator field, based on the use of a redox-active conducting polymer, polypyrrole (PPy) and a natural polymer, polydopamine (PDA). Based on their redox-active potentials, the PPy-based redox-active separator was designed to contribute capacity to the cathode of a LIB, while the PDA-based redox-active separator was proposed to be used on the anode side.It is known that a homogeneous current distribution is beneficial for the battery performance. Therefore, two new types of separators with homogenous pore distributions have been manufactured to study the influence of the pore distribution on the Li deposition/stripping behavior and composite cathode utilization in LMBs. With the knowledge obtained from the study, a stable, long lifetime paper-based LMB was designed.
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| 7. |
- Ruan, Chang-Qing
(författare)
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Functionalization, Characterization and Applications of Oxidized Nanocellulose Derivatives
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose, a sustainable raw material derived from nature, can be used for various applications following its functionalization and oxidation. Nanocellulose, inheriting the properties of cellulose, can offer new properties due to nanoscale effects, in terms of high specific surface area and porosity. The oxidation of cellulose can provide more active sites on the cellulose chains, improving its functionalization and broadening applications. Two kinds of oxidation and their corresponding applications are described in this thesis: periodate oxidation and Oxone® oxidation.2,3-dialdehyde cellulose (DAC) beads were prepared from Cladophora nanocellulose via periodate oxidation, and were further modified with amines via reductive amination. Several diamines were selected as possible crosslinkers to produce porous DAC beads, which showed higher porosity, stability in alkaline solution and enhanced thermal stability.After functionalization of DAC beads with L-cysteine (DAC-LC), thiol, amine and carboxyl groups were introduced into the DAC beads, endowing the DAC-LC beads with high adsorption capacity for palladium. The synthesized DAC-LC beads were characterized with SEM, FTIR, XPS, TGA, BET and XRD and the palladium adsorption process was investigated.Chitosan was employed as a crosslinker in functionalization of DAC beads (DAC-CS). The conditions for the synthesis of DAC-CS beads were screened and verifying the stability of the beads in alkaline solution. The DAC-CS beads produced were investigated using SEM, FTIR, XPS, TGA and BET, and the adsorption and desorption capacity of Congo red was studied, indicating DAC-CS beads have potential as sorbent.Oxone oxidation of cellulose is a novel one-pot oxidation method in which mainly the hydroxyl groups on C6 are oxidized to produce carboxylic acid groups on the cellulose chains. To increase the efficiency of Oxone oxidation, several reaction parameters were studied. Cellulose pulp and Cladophora nanocellulose were chosen as prototypes to investigate the effects of oxidation, and the physicochemical properties of the oxidized products were characterized. Cellulose pulp, pretreated with Oxone oxidation, was disintegrated by homogenization to prepare cellulose nanofibers (CNF). The effect of pretreatment on the preparation of CNF was studied, and the results indicated that Oxone oxidation was efficient in the production of CNF.
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| 8. |
- Brohede, Ulrika, 1969-
(författare)
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Drug Diffusion and Nano Excipient Formation Studied by Electrodynamic Methods
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- New smart drugs demand new smart drug delivery systems and also new smart analysis methods for the drug delivery process and material characterization. This thesis contributes to the field by introducing a new electrodynamic approach for studying the drug diffusion proc-esses as well as the formation of a new type of drug delivery systems, the so called mesoporous nano excipients.Drug diffusion processes from different pharmaceutical materials were examined. The transport of charged drug substances was investigated by electrodynamic methods; either as a release process governed by diffusion using the alternating ionic current method or by applying a voltage, sinusoidal or dc, to force the drug ions to move in an electric field.Temperature-dependent drug release from microcrystalline cellulose tablets was examined in order to extract information about the diffu-sion process. Percolation theory was also employed to binary mixtures of an insoluble and electrically insulating matrix material together with a soluble and ionic conducting drug. Further, dielectric spectros-copy was proven to be a powerful method for examining the state of vesicle formation of drug and surfactant molecules in a carbopol gel. Finally, a new potential class of pharmaceutical materials were exam-ined, namely the AMS-n mesoporous materials, showing that the al-ternating ionic current method is powerful both in the study of the synthesis of and in the release process from these.
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