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Towards stimuli-reformable paperboard and flipped classroom in chemistry education : A study of how to create a paper with controllable mechanical properties and a study in how the flipped classroom is used in chemistry education / Omformbar kartong och Flippat klassrum i kemiundervisning : En studie av hur papper kan få mekaniska egenskaper som kontrollerbart går att förändra samt av hur metoden Flipped Classroom används i kemiundervisningPettersson, David January 2017 (has links)
Today, paper and paperboard is an important part of the packaging industry, as well as natural part of our daily lives. The alternatives to paper and paperboard is often produced from nonrenewable sources such as petroleum and as demands on sustainability increase in the packaging sector, it gives paper a desirable advantage over plastics. To increase the use of paper, some of the limiting factors for paper needs to be overcome, such as its limited formability. One way to create a paper that can be formed in new ways is to imbibe the paper with an additive that makes its modulus changeable. This would make it possible to control the stiffness of the paper which would make it more formable. This have been the aim of this thesis. To create this formable paper four different approaches were used. Of these four, three included how paper can be treated with polyelectrolytes to be able to increase its modulus when stimuli are applied. The two first approaches were based on the layer-by-layer technique adsorbing alginate and cationic fibrils to form a layer that could be cross-linked, either on the surface of a film (the first approach) or in the network of fibres in a porous paper (the second approach). The last approach was to impregnate the papers with alginate. The results show that the first approach gave a too low adsorption of polyelectrolytes, why no difference could be detected. The second approach resulted in a higher adsorbed amount, but the effects were still too small. The third approach gave a paper which could, depending on the concentration of alginate, either increase or decrease its modulus when cross-linked. The last approach was to create a laminate, using unmodified fibers together with dialcohol cellulose fibres. This resulted in a paper that could be formed using heat and allowing the paper to cool down in the desirable form. In the curriculum for chemistry in Swedish high schools there is a paragraph that says that research in chemistry should be a part of the content the students learn. This is a challenge both to teachers and researchers. For teachers, to find research at an appropriate level and teach it in an understandable way. For researchers, to communicate the research so it is understandable for society. With this as a motivation, a second part of this thesis discuss the method flipped classroom in chemistry education at Swedish high schools. It was seen that from the teacher’s perspective, flipped classroom meant advantages that could be categorized into five categories. The categories that was found were Time to interact, Student responsibility, dialogue, laboratory work and understanding and using the language. / Pappers- och kartongindustrin är idag en viktig del av förpackningsindustrin. Alternativ till kartong är ofta producerat av icke-förnybara råvaror och idag när kraven på hållbarhet ökar ger detta kartong en fördel mot plast. För att öka användningsområdena för kartong så måste de begränsningar som materialet har idag övervinnas. Detta gäller till exempel formbarheten. Ett sätt att skapa kartong som kan bli format på nya sätt är att göra en additiv tillsats till papperet som har egenskapen att det kan variera sin styvhet. Detta skulle göra det möjligt att kontrollera papperets styvhet, vilket har varit målet för det här arbetet. Genom att använda fyra olika arbetssätt har denna egenskap försökts åstadkommas. Tre av arbetssätten har behandlat papper med polyelektrolyter vars E-modul kan ökas med hjälp av något stimuli. I de två första försöken applicerades polyelektrolyterna genom den så kallade lager-på-lager-tekniken, där alginat och katjoniska cellulosafibriller adsorberades, i första försöket på ytan av en film och i det andra på ytan av fibrerna i fibernätverket i ett poröst papper. I det tredje försöket impregnerades de orösa papperna med alginat. Resultatet från det första försöket var att adsorptionen inte gav någon effekt eftersom den absorberande mängden var för låg. I det andra försöket var adsorptionen högre men det påverkade inte de mekaniska egenskaperna nämnvärt. I det tredje försöket med impregnering så kunde en ändring av E-modulen observeras när systemet tvärbands. I det sista försöket användes en metod som byggde på laminering. Ett ark av modifierade fibrer guskades ihop med ett ark med dialkoholcellulosefibrer. De försök som gjordes tyder på att papperet kunde formas och kunde fås att behålla formen om det värmdes och kyldes i den önskade formen. I läroplanen för kemi på gymnasiet finns en paragraf som beskriver hur kemiundervisningen ska ha inslag av forskning. Detta är en utmaning för både lärare och forskare. Lärarnas utmaning består i att finna forskning på en bra nivå för eleverna och att förklara den på ett förståeligt sätt. För forskare består utmaningen i att kommunicera forskningen på ett förståeligt sätt till samhället. Med detta som motivering har detta arbete en utbildningsdel. I den har lärares perspektiv på metoden ”flipped classroom” i kemiklassrummet undersökts. Flipped classroom beskrevs ha styrkor och dessa kunde kategoriseras i fem kategorier. Kategorierna var tid för interaktion, elevens ansvar, dialog, laborationer och förstå och använda språket.
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Studies of Macromolecule/Molecule Adsorption and Activity at InterfacesLiu, Jianzhao 03 January 2020 (has links)
Interfaces are ubiquitous in our daily life. A good understanding of the interfacial properties between different materials, or a single material in different physical states is of critical importance for us to explore the current world and bring benefits to mankind. In this work, interfacial behavior was investigated with the help of surface analysis techniques, such as quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and atomic force microscopy (AFM), in order to gain better understanding on biofuel conversion, gene/drug delivery, and chemical fixation of CO2.
Biomimetic chelator-mediated Fenton (CMF) non-enzymatic degradations on cellulose and chitin thin films was studied by liquid-phase QCM-D and AFM. QCM-D is a powerful tool to monitor the kinetics of hydrolysis of regenerated cellulose and chitin model surfaces. Results from QCM-D and AFM showed that the majority of the biomass of the two model surfaces can be hydrolyzed by the CMF system. The initial degradation rates for both model surfaces by the CMF system are faster than that of the corresponding enzyme systems. The CMF system, which is a good non-enzymatic pretreatment agent for cellulose and chitin, may work on a wide variety of polysaccharide systems.
Adsorption of cationic cellulose derivatives onto self-assembled monolayer (SAM) surfaces was investigated using liquid-phase SPR. Results from SPR showed that depending upon the cellulose derivative structure, irreversible adsorption ranging from a monolayer to ~1.6 layers of cellulose derivative were formed on the SAM-COOH surface based upon a charge neutralization mechanism. At low salt concentrations, the long-range electrostatic attraction between the cationic cellulose derivatives (6-PyrCA and 6-MeIMCA) and the SAM surfaces facilitates the formation of a 2-dimensional monolayer. While, for TMACE, the energy gained through the hydrophobic interaction between adjacent long polyelectrolyte branches may afford the electrostatic repulsion and chain entropy penalties, resulting in the formation of 3-dimensional adsorbed polyelectrolyte layers.
Adsorption of 1,2-epoxybutane gas molecules onto/into VPI-100 metal–organic frameworks (MOFs) was studied by gas-phase QCM-D experiments. Results from QCM-D demonstrated that VPI-100 (Ni) MOFs have higher irreversible adsorption per unit cell (θ) and faster diffusion coefficients (D) than VPI-100 (Cu) MOFs. The presence of bound counter-balancing ions on the metallo-cyclam core was attributed as the cause of the higher θ and faster D through the Ni analogue, which suggests the MOF-epoxide interaction occurs at the metallo-cyclam. This study shed light upon tuning MOF structures for better CO2 sorption and epoxide activation to gain higher catalytic efficiency.
Finally, in operando high energy X-ray diffraction (HEXRD) was used to monitor the phase transition of the NaxNi1/3Co1/3Mn1/3O2 cathode material during the sintering process. The first charge/discharge cycle of the NaxNi1/3Co1/3Mn1/3O2 cathode materials in different phases were also studied by in operando HEXRD. It was found that the intergrowth P2/O1/O3 cathode (NCM-Q cathode) can inhibit the irreversible P2–O2 phase transition and simultaneously improve the structural stability of the O3 and O1 phases during cycling. The NCM-Q cathode with triple-phase integration demonstrates highly reversible phase evolution during high voltage cycling, possibly leading to a highly reversible capacity and good cycle stability. / Doctor of Philosophy / Interfaces and surfaces are everywhere. Many critical processes, such as molecular recognition, catalysis, and charge transfer, take place at interfaces. The surfaces of plants and animals provide barriers from pathogens, prevent damage from mechanical impacts, detect external stimuli, etc. Inside the human body, nutrition and oxygen are adsorbed through interactions between substances and cell surfaces. Investigations of interfacial behaviors may help us understand our current world better and bring benefits to mankind. In this dissertation, the interface between bio-renewable natural polymers and biomimetic chelators, the interface between a self-assembled monolayer and cationic cellulose derivatives, and the interface between metal–organic frameworks (MOF) and 1,2-epoxybutane gas molecules, were studied with a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and atomic force microscopy (AFM), to gain insights into biofuel conversion, gene/drug delivery and chemical fixation of CO2, respectively. Additionally, thermally and electrochemically induced phase transitions in sodium-ion battery (SIB) cathode materials were probed via in operando high energy X-ray diffraction (HEXRD).
Biomimetic chelator-mediated Fenton (CMF) non-enzymatic degradations of cellulose and chitin thin films were studied by liquid-phase QCM-D and AFM. It was found that the majority of the biomass of the two model surfaces can be degraded by the CMF system. Adsorption of cationic cellulose derivatives onto self-assembled monolayer (SAM) surfaces was investigated using liquid-phase SPR. It was found that both the absorbed layer conformation and the absorbed amount depend upon the interplay between long-range electrostatic interactions and short-range interactions. Adsorption of 1,2-epoxybutane gas molecules onto/into VPI-100 MOFs was studied by gas-phase QCM-D experiments. Data from QCM-D revealed the irreversible gas molecule absorption onto/into MOFs and shed light upon tuning MOF structures for better CO2 sorption and epoxide activation to gain higher catalytic efficiency. Finally, the in operando high energy X-ray diffraction (HEXRD) was used to probe thermally and electrochemically induced phase transitions in sodium-ion battery (SIB) cathode materials. It was found that the NCM-Q cathode with triple-phase integration demonstrates highly reversible phase evolution during high voltage cycling, possibly leading to a highly reversible capacity and good cycle stability.
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Synthesis and Applications of Cellulose Derivatives for Drug DeliveryMarks, Joyann Audrene 14 September 2015 (has links)
In an effort to produce new derivatives of cellulose for drug delivery applications, methods were developed to regioselectively modify C-6 halo cellulose esters to produce cationic derivatives via nucleophilic substitution. Reaction of C-6 substituted bromo and iodo cellulose with trialkylated amines and phosphines produced new cationic ammonium and phosphonium cellulose derivatives which can be explored as delivery agents for nucleic acids, proteins and other anionic drug molecules. It was anticipated that these new derivatives would not only be capable of complexing anionic drug molecules but would have greatly improved aqueous solubility compared to their precursors. The phosphonium derivatives described in this work are an obvious example of such improved solubility properties.
Given the importance of cellulose derivatives in making amorphous dispersions with critical drugs, it has also been important to analyze commercially available polymers for the potential impact in oral drug delivery formulations. To do so pairwise blends of cellulosics and synthetic polymers commonly used as excipients were tested for miscibility using techniques such as DSC, mDSC, FTIR and film clarity. Miscible combinations highlight the potential to use combinations of polymers currently available commercially to provide drug delivery solutions for specific drug formulations.
The use of melt extrusion in processing some of these drug/polymer dispersions provides a means of highlighting the capability for the use of these cellulosics in melt extruded amorphous dispersions. This solvent free, high pressure method significantly reduces cost and time and can be applied on a large scale. The analysis of long chain cellulose esters and ultimately the novel omega carboxy esters for melt processability significantly impacts the possibilities available for use of those excellent drug delivery agents on a much larger scale. / Ph. D.
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[pt] DESENVOLVIMENTO DE EMULSÕES ÓLEO EM ÁGUA ESTABILIZADAS POR MATERIAIS SUSTENTÁVEIS PARA LIBERAÇÃO CONTROLADA DE N, N -DIETIL-3-METILBENZAMIDA (DEET)) / [en] DEVELOPMENT OF OIL-IN-WATER EMULSIONS STABILIZED BY SUSTAINABLE MATERIALS FOR CONTROLLED RELEASE OF N, N -DIETHYL-3- METHYLBENZAMIDE (DEET)LUIS MIGUEL GUTIERREZ BELENO 27 June 2024 (has links)
[pt] Os mosquitos são os principais vetores de transmissão de doenças como zika,
dengue e chikungunya, causando mais de 700 mil casos por ano. O uso de repelentes,
principalmente formulações tópicas, é uma das melhores medidas de proteção para
reduzir e/ou prevenir a transmissão de muitas doenças transmitidas por insetos. Neste
trabalho, formulamos emulsões de DEET/óleo em água para liberação controlada de
repelentes como estratégia para desenvolver formulações repelentes com tempo de
proteção superior a 6 h. Investigamos os efeitos do valor de HLB na estabilidade e
viscosidade das emulsões, usando uma mistura de surfactantes (Span 80 e Tween 80)
para formular emulsões em uma faixa de HLB entre 4-14. Também avaliamos o
tamanho das gotas, comportamento reológico, método de mistura e índice de
estabilidade da emulsão. As emulsões de DEET-óleo-em-água desenvolvidas
contendo N, N-dietil-3-metilbenzamida (DEET) foram estabilizadas usando dois
nanomateriais carregados negative e positivamente, nanopartículas de sílica (SiNP) e
nanofibrilas de celulose catiônica (CCNF), e uma mistura de surfactantes não iônicos
de grau para evitar a precipitação por agregação eletrostática. Os resultados indicam
que no HLB 10, esta mistura pode estabilizar as emulsões independentemente do tipo
de óleo (mineral ou vegetal), e as emulsões apresentam comportamento newtoniano
independentemente do método de mistura. As formulações foram estáveis por mais de
quatro meses à temperatura ambiente, mostrando-se fortemente resistentes à
desestabilização por estresse centrífugo e térmico quando se utiliza nanomateriais em
combinação com surfactantes. O CCNF e o SiNP mantiveram a distribuição
granulométrica estável devido ao aumento da viscosidade da fase contínua. A ação
combinada desses materiais na estabilização da fase oleosa contendo DEET diminuiu
significativamente a taxa de liberação do composto ativo em comparação com o DEET
não emulsificado, produzindo uma liberação sustentada de DEET nas primeiras 6 h. / [en] Mosquitoes are the main vectors of transmission of diseases such as zika, dengue and
chikungunya, causing more than 700,000 cases per year. The use of repellents, mainly
topical formulations, is one of the best protective measures to reduce and/or prevent
the transmission of many insect-borne diseases. In this work, we formulated DEET/oil-in-water emulsions for the controlled release of repellents as a strategy to develop
repellent formulations with a protection time greater than 6 h. We investigated the
effects of the HLB value on the stability and viscosity of the emulsions, using a blend
of surfactants (Span 80 and Tween 80) to formulate emulsions in an HLB range
between 4-14. We also evaluated droplet size, rheological behavior, mixing method
and emulsion stability index. The developed DEET-oil-in-water emulsions containing
N, N-diethyl-3-methylbenzamide (DEET) were stabilized using two positively and
negative charged nanomaterials, silica nanoparticles (SiNP) and cationic cellulose
nanofibrils (CCNF), and a blend of food-grade nonionic surfactants to prevent
precipitation by electrostatic aggregation. The results indicate that at HLB 10, this
mixture can stabilize the emulsions regardless of the type of oil (mineral or vegetable),
and the emulsions present Newtonian behavior regardless of the mixing method. The
formulations were stable for more than four months at room temperature, showing to
be strongly resistant to destabilization by centrifugal and thermal stress when using
nanomaterials in combination with surfactants. The CCNF and SiNP kept the droplet
size distribution stable due to the increase in the viscosity of the continuous phase. The
combined action of these materials in stabilizing the DEET-containing oil phase
significantly decreased the rate of active compound release compared to non-emulsified DEET, producing a sustained release of DEET within the first 6 h.
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