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Strategies for improving mechanical properties of polypropylene/cellulose compositesEspert, Ana January 2005 (has links)
The interest for polypropylene/cellulose composites has experienced a great increase in different applications such as car interiors and construction materials. Cellulose fibres are inexpensive, renewable, biodegradable, they present lower density and their mechanical properties can be compared to those of inorganic fillers. However, several factors must be considered when designing polypropylene/cellulose composites: the poor compatibility between the hydrophilic fibres and the hydrophobic thermoplastic matrix leads to a weak interface, which has to be improved by coupling agents; the hydrophilic nature of the fibres makes them very sensitive towards water absorption, which also leads to a loss of properties and swelling with subsequent dimensional instability; the reduced thermal stability of cellulose fibres leads to degradation of the fibres at thermoplastic processing temperatures producing odours in the final material; and finally the properties of composites are greatly influenced by the structure, size and quality of the fibres. Pulp fibres modified by different methods in order to enhance the compatibility fibre-matrix, were tested. Modified fibres led to improved mechanical properties and thermal behaviour when used in composites with recycled polypropylene. Four different types of natural fibres were used as reinforcement in two different polypropylene types: virgin and recycled polypropylene. The mechanical properties of the composites were mostly dependent on the fibre loading and slightly dependent on the type of fibre. Moreover, water absorption kinetics was studied by the Fickian diffusion theory. After absorption, a remarkable loss of properties was observed. Hydrolysed cellulose fibres showed a greater enhancing effect on polypropylene than non-hydrolysed cellulose fibres. This is attributed to the greater mechanical properties of reduced cellulose structures. The effect of using cellulose fibres in PP/clay nanocomposites was also studied. The interaction between the clay particles and the cellulose fibres and the combined effect of both reinforcements were believed to be the main reasons for the enhancing properties. / QC 20101011
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Natural products from nonracemie building blocks : synthesis of pine sawfly pheromonesLarsson, Michael January 2005 (has links)
This thesis describes a number of synthetic approaches for obtaining chiral, enantiomerically pure natural products, in particular some semiochemicals. This has been accomplished by using various strategies; by starting from compounds from the chiral pool, by using chiral auxiliaries, via enzymatic resolutions or by chemical asymmetric synthesis. Hence, the sexual pheromone of Microdiprion pallipes, a propanoate ester of one or several isomers of 3,7,11-trimethyltridecan-2-ol, was synthesised, both as a mixture of all isomers and as the sixteen pure, individual stereoisomers. These compounds were obtained by joining different enantiopure building blocks stemming from the chiral pool. When compared with some synthetic blends, both the propanoate esters of the stereoisomeric erythro-3,7,11-trimethyltridecan-2-ols originally found in the extract from the female of M. pallipes, surprisingly, showed lower activities in biological studies. Indeed, the propanoates of two threo-isomers gave significantly higher responses in biological tests, than did the propanoates of the two natural erythro-ones. Because the synthetic strategy used earlier was not very efficient for the preparation of the threo-isomers of 3,7,11-trimethyltridecan-2-ol, we were encouraged to look for alternative synthetic approaches. The new synthetic strategy chosen led us to two key synthetic building blocks, an O-protected derivative of (2S,3S)-3-methyl-4-(phenylsulfonyl)butan-2-ol butanol and (3R,7R)-1-iodo-3,7-dimethylnonane. Deprotonation of the former followed by alkylation with the latter should give a compound with the desired carbon skeleton. For efficient preparation of the first building block, we developed a new diastereoselective addition reaction of dialkylzincs to some chiral aldehydes, the products of which were diastereomerically enriched 1,2-dialkyl-alkanols. Using this method, each enantiomer of the desired building block was obtained via efficient diastereoselective addition of dimethylzinc to each enantiomer of a 2-methylaldehyde. The resulting product, a diastereomerically and enantiomerically highly enriched 3-methyl-2-alkanol was further purified by enzyme catalysed acylation followed by some functional group interconversions. The second building block was prepared via convergent multistep synthesis, starting from a single, enantiomerically pure compound, (R)-2-methylsuccinic acid 4-t-butyl ester, derived from the chiral pool. The two enantiomerically pure building blocks, so obtained, were coupled together. Some additional functional group manipulations of the product produced furnished the desired isomer, which had shown the highest activity in field tests of the M. pallipes, namely the propanoate ester of (2S,3R,7R,11R)-3,7,11-trimethyltridecan-2-ol. This thesis describes a number of synthetic approaches for obtaining chiral, enantiomerically pure natural products, in particular some semiochemicals. This has been accomplished by using various strategies; by starting from compounds from the chiral pool, by using chiral auxiliaries, via enzymatic resolutions or by chemical asymmetric synthesis. Hence, the sexual pheromone of Microdiprion pallipes, a propanoate ester of one or several isomers of 3,7,11-trimethyltridecan-2-ol, was synthesised, both as a mixture of all isomers and as the sixteen pure, individual stereoisomers. These compounds were obtained by joining different enantiopure building blocks stemming from the chiral pool. When compared with some synthetic blends, both the propanoate esters of the stereoisomeric erythro-3,7,11-trimethyltridecan-2-ols originally found in the extract from the female of M. pallipes, surprisingly, showed lower activities in biological studies. Indeed, the propanoates of two threo-isomers gave significantly higher responses in biological tests, than did the propanoates of the two natural erythro-ones. Because the synthetic strategy used earlier was not very efficient for the preparation of the threo-isomers of 3,7,11-trimethyltridecan-2-ol, we were encouraged to look for alternative synthetic approaches. The new synthetic strategy chosen led us to two key synthetic building blocks, an O-protected derivative of (2S,3S)-3-methyl-4-(phenylsulfonyl)butan-2-ol butanol and (3R,7R)-1-iodo-3,7-dimethylnonane. Deprotonation of the former followed by alkylation with the latter should give a compound with the desired carbon skeleton. For efficient preparation of the first building block, we developed a new diastereoselective addition reaction of dialkylzincs to some chiral aldehydes, the products of which were diastereomerically enriched 1,2-dialkyl-alkanols. Using this method, each enantiomer of the desired building block was obtained via efficient diastereoselective addition of dimethylzinc to each enantiomer of a 2-methylaldehyde. The resulting product, a diastereomerically and enantiomerically highly enriched 3-methyl-2-alkanol was further purified by enzyme catalysed acylation followed by some functional group interconversions. The second building block was prepared via convergent multistep synthesis, starting from a single, enantiomerically pure compound, (R)-2-methylsuccinic acid 4-t-butyl ester, derived from the chiral pool. The two enantiomerically pure building blocks, so obtained, were coupled together. Some additional functional group manipulations of the product produced furnished the desired isomer, which had shown the highest activity in field tests of the M. pallipes, namely the propanoate ester of (2S,3R,7R,11R)-3,7,11-trimethyltridecan-2-ol. This thesis describes a number of synthetic approaches for obtaining chiral, enantiomerically pure natural products, in particular some semiochemicals. This has been accomplished by using various strategies; by starting from compounds from the chiral pool, by using chiral auxiliaries, via enzymatic resolutions or by chemical asymmetric synthesis. Hence, the sexual pheromone of Microdiprion pallipes, a propanoate ester of one or several isomers of 3,7,11-trimethyltridecan-2-ol, was synthesised, both as a mixture of all isomers and as the sixteen pure, individual stereoisomers. These compounds were obtained by joining different enantiopure building blocks stemming from the chiral pool. When compared with some synthetic blends, both the propanoate esters of the stereoisomeric erythro-3,7,11-trimethyltridecan-2-ols originally found in the extract from the female of M. pallipes, surprisingly, showed lower activities in biological studies. Indeed, the propanoates of two threo-isomers gave significantly higher responses in biological tests, than did the propanoates of the two natural erythro-ones. Because the synthetic strategy used earlier was not very efficient for the preparation of the threo-isomers of 3,7,11-trimethyltridecan-2-ol, we were encouraged to look for alternative synthetic approaches. The new synthetic strategy chosen led us to two key synthetic building blocks, an O-protected derivative of (2S,3S)-3-methyl-4-(phenylsulfonyl)butan-2-ol butanol and (3R,7R)-1-iodo-3,7-dimethylnonane. Deprotonation of the former followed by alkylation with the latter should give a compound with the desired carbon skeleton. For efficient preparation of the first building block, we developed a new diastereoselective addition reaction of dialkylzincs to some chiral aldehydes, the products of which were diastereomerically enriched 1,2-dialkyl-alkanols. Using this method, each enantiomer of the desired building block was obtained via efficient diastereoselective addition of dimethylzinc to each enantiomer of a 2-methylaldehyde. The resulting product, a diastereomerically and enantiomerically highly enriched 3-methyl-2-alkanol was further purified by enzyme catalysed acylation followed by some functional group interconversions. The second building block was prepared via convergent multistep synthesis, starting from a single, enantiomerically pure compound, (R)-2-methylsuccinic acid 4-t-butyl ester, derived from the chiral pool. The two enantiomerically pure building blocks, so obtained, were coupled together. Some additional functional group manipulations of the product produced furnished the desired isomer, which had shown the highest activity in field tests of the M. pallipes, namely the propanoate ester of (2S,3R,7R,11R)-3,7,11-trimethyltridecan-2-ol. / QC 20101026
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Bioorganisk fastfas syntes för att skapa intelligenta ytor / Solid-phase bio-organic synthesis to create intelligent surfacesNygren, Patrik January 2004 (has links)
This thesis investigates three different surface modifications, and the route to design and synthesize them. The thesis is therefore divided into three sub- projects. (i.) Design and synthesis of a peptide which secondary structure could be controlled by a negatively charged surface. (ii.) Design and synthesis of a cyclic peptide, that would self-organize prior to surface interaction, using the type I anti-freeze protein of a winter flounder as template. (iii.) The use of solid-phase synthesis to make the synthesis of SAM-molecules easier.
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Solid-Phase Microextraction in Polymer Analysis - Extraction of Volatiles from Virgin and Recycled Polyamide 6.6Gröning, Mikael January 2004 (has links)
<p>The extraction and quantitative analysis of low molar mass compounds in polymers is an analytical challenge. It is also important from a practical point of view because the low molar mass compounds in time will migrate from the polymers into the surrounding environment. It is especially important to gain knowledge about the migrating compounds in applications such as medical implants, packaging materials and car interiors. The main aim of this thesis was to develop headspace solid phase microextraction (HS-SPME) methods to meet this challenge. In addition, the work aimed to show the applicability of the methods developed in quality control of polymers, degradation studies and assessment of polymer durability. </p><p>Factors influencing the extraction of low molar mass compounds from polyamide 6.6 were studied. Particular attention was paid to the matrix effects and to the establishment of headspace equilibrium of 2-cyclopentyl-cyclopentanone in solid polyamide. Hydrogen bonding and adsorption of analyte to the polar matrix was observed and found to cause exceedingly slow establishment of equilibrium. The adsorption could be eliminated by the addition of water, which replaced 2-cyclopentyl-cyclopentanone at the adsorption sites of the polyamide and made it possible to measure the 2-cyclopentyl-cyclopentanone content in polyamide 6.6 using multiple headspace solid-phase microextraction (MHS-SPME). </p><p>A correlation between the emitted amount of 2-cyclopentyl-cyclopentanone and the amount 2-cyclopentyl-cyclopentanone in the material was found. The correlation was valid also under non-equilibrium conditions, which allows rapid assessment of the 2-cyclopentyl-cyclopentanone content in polyamide 6.6 using headspace sampling. </p><p>20 different low molar mass compounds were identified in virgin and recycled polyamide 6.6. The compounds could be classified into four groups: cyclic imides, pyridines, chain fragments and cyclopentanones. The structures of the degradation products imply that the thermo-oxidative degradation starts at the N-vicinal methyl group. Larger amounts of degradation products at lower degree of degradation were formed in recycled than in virgin polyamide 6.6. Thus, processing increases the susceptibility of polyamide 6.6 to thermal oxidation. The total amount of cyclopentanones was reduced upon processing and oxidation. Cyclopentanones are thus not thermo-oxidation products of polyamide 6.6. N-pentyl-succinimide showed the most significant increase due to oxidation and processing. The formation of N-pentyl-succinimide was in correlation with the simultaneous changes in tensile strength. The largest increase in N-pentyl-succinimide coincided with the largest drop in tensile strength.</p>
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Stereoselective syntheses of semichemicals : Applications in ecological chemistrySantangelo, Ellen M. January 2004 (has links)
<p>This thesis describes the syntheses of semiochemicals and their applications in the development of control methods for pest insects. The compounds synthesized are divided into three groups: 1) Lepidoptera pheromones; 2) methyl substituted chiral pheromones and 3) aphid pheromones. </p><p>Different purification techniques have been explored in order to provide > 99% pure semiochemicals for field tests. Examples of the techniques are uses of urea inclusion complexes, argentum chromatography, low temperature crystallization and what we call the Baeckström isolation technique.</p><p>Iridoids have been produced in a synthetic strategy including an intramolecular enal-enamine [4+2] cycloaddition, a dynamic acetylation and an enantioselective transesterification mediated by a lipase from Pseudomonas cepacia. The use of chiral auxiliaries to perform the intramolecular [4+2] cycloaddition has also been investigated. A useful asymmetric route to iridoids has been developed.</p>
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Synthesis of Organic Compounds for Nuclide Therapy : Derivatives of Carboranes, 9-Aminoacridine and AnthracyclinesGhirmai, Senait January 2004 (has links)
This thesis addresses the synthesis of organic compounds, some of them are derivatives of compounds with DNA binding properties, for potential use in targeted nuclide therapy. The compounds synthesized therefore also need to contain potent nuclides. Here the nuclides considered are the radionuclide 125I, and the stable isotope 10B, which becomes radioactive upon neutron activation. 125I is an Auger-electron emitter, which emits particles that can travel only about 1-2 µm through human tissue and hence has to be delivered to the cancer cell nucleus to cause DNA damage. Neutron activated 10B emits highly cell killing α-particles and 7Li3+ ions, the application of which in Boron Nuclide Capture Therapy (BNCT) has proven very promising. The thesis can be divided into three parts: i) A nido-carborate, 7-(3´-ammoniopropyl)-7,8-dicarba-nido-undecaborate(-1), has been synthesized and radioiodinated for use as a pendant group for attachment of 125I to tumor-seeking macromolecules. Radiolabeling was achieved in greater than 95% yield. ii) Both enantiomers of m-carboranylalanine, a carborane analogue of phenylalanine, have been prepared in high enantiomeric excess, and are of potential interest in BNCT. The synthesis involved amination of the N-acyl derivative formed from [3-(1,7-dicarba-closo-dodecarborane(12)-1-yl)-2-propanoic acid and Oppolzer’s camphor sultam. iii) Derivatives of the DNA intercalating compounds 9-aminoacridine, daunorubicin and doxorubicin have been synthesized and labeled with 125I. The 9-aminoacridines were synthesised with a variety of functional groups such as carboxyl, amino and hydroxyl. The anthracylines daunorubicin and doxorubicin are efficient chemotherapeutic agents; the synthesis routes of ester, amide and amine derivatives of these compounds are presented. The Chloramine T method was used for the radioiodinations, and the radioiodination precursors of both the acridine and the anthracycline derivatives, were made to contain either a trimethylstannyl group or a phenolic substituent. In the former case the trimethylstannyl group was replaced by 125I, and in the latter case, the compounds were radiolabeled directly at the o- position to the phenolic hydroxyl group. Both methods gave high radiolabeling yields.
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Charge-transfer excitations and phtophysical properties of molecular building blocksRubio Pons, Oscar January 2005 (has links)
This thesis reports a state-of-the-art theoretical study of photophysical properties of organic charge-transfer aromatic molecules. These molecules are building blocks of molecular functional materials used in modern photonics technology and play essential roles in chemistry and biology in general. A good understanding of these systems is thus important. The theoretical results for permanent dipole moments of some substituted benzenes have been obtained using the coupled cluster singles and doubles (CCSD) method. The performance of density functional theory (DFT) for the geometry and electronic properties has been compared with that of traditional ab initio methods, such as Hartree-Fock, second-order Möller Plesset perturbation theory (MP2), CCSD and CCSD(T). Limitations of the DFT methods for charge transfer molecules have been demonstrated. The multi-configuration self-consistent field (MCSCF) method has been applied to understand properties of the triplet states of benzene derivatives by studying their phosphorescence with the inclusion of contributions from vibronic coupling. It has also been employed to calculate the photophysics of the thioxanthone molecule containing three benzene rings in combination with the CASPT2 method, resolving a long-standing problem concerning the possible stable conformations of the molecule. With knowledge of the building blocks a series of porphyrin derivatives with exceptionally large two-photon absorption cross sections were designed, and proposed for use in bioimaging applications. The static and dynamic properties of a few zinc and platinum organometallic compounds, being possible candidates for optical limiting devices, have also investigated. / QC 20101011
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Electrochemical Aspects of Miniaturized Analytical PlatformsKlett, Oliver January 2003 (has links)
This thesis ties some electrochemical aspects of development and fabrication of an analytical system on a microchip together. These aspects develop through the fundamentals of amperometric detection in microsystems and microfabrication via the interaction of electrochemical detection and electrophoretic separation finally to the interfacing of a microsystem to the macro world. Paper I deals with amperometric detection in microscale systems and describes the fabrication of the necessary on-chip microelectrodes together with fluidic channels in silicon. It was furthermore studied, if the interelectrode distance of some μm could be used to improve the sensitivity in amperometric detection by employing redox cycling. Papers II, III and IV deal with the effect of a high voltage field on amperometric detection. In analytical microdevices typically an electrophoretic separation step (e.g. capillary electrophoresis, CE) precedes the detection. The interference of the CE high voltage with the amperometric detection potential is often considered one of the main hindrances for an effective combination of these techniques. In paper II one reason for the observed disturbing potential shift was elucidated. It was shown that positioning of working electrode and reference electrode on an equipotiental surface eliminates this problem. Paper III reports an application of this technique. In paper IV it could be shown that this approach could further be used to significantly reduce the instrumental requirements for amperometric detection in CE. Papers V, VI, VII, finally discuss the interfacing of low volumetric flows that typically occur on microanalytical devices to other techniques. Both, interfacing from liquid to liquid phase (μLC to CE in paper V) and from liquid to gas phase (CE to MS in paper VI and VII) were discussed. Electrochemical methods are used in this context to evaluate the stability and, in paper VI and VII, to increase the understanding of underlying processes of corrosion.
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"Jag är en smältmaskin!" : En intervjustudie baserad på förskolebarns tankar om vattnets fasövergångar / "I am a melting machine!” : An interview study based on preschool children's thoughts about the water's phase transitionsReuterdahl Palm, Josefine January 2018 (has links)
The purpose with my study is to investigate what kind of thoughts children between three or four years express about the water's phase transitions. The theoretical perspective which has been used is sociocultural perspective. The method is based on semi-structured interviews in groups. The interview groups consist two to three children in each group. The interviews are based on open questions, where the children's thoughts, own words and explanations are in focus. This is documented with audio recording and supplemented with field notes.The result shows that the children have some understanding about the water's phase transitions. Conclusions that can be made is that children think that the water can transform from solid to liquid form but not the other way around. A recurring thought that children have when water freezes is that you need to mix cold water with something and stir it around. Children believe that the temperature is of significance when ice melts or creates. They also think that weather conditions are of significance to phase transitions. When the ice melts children thinkt hat the water is moved and has disappeared. Several thoughts that the children in my study have can be seen in previous research. / Syftet med min studie är att undersöka vilka tankar barn mellan tre till fyra år uttrycker när de undersöker vattnets fasövergångar. Det teoretiska perspektivet som använts är sociokulturellt perspektiv. Metoden är baserad på semi-strukturerad intervju i grupp. Intervjugrupperna består av två till tre barn i varje grupp. Intervjun består av öppna frågor där barnens tankar, egna ord och förklaringar är i fokus. Detta dokumenteras med ljudinspelning som kompletteras med fältanteckningar. Resultatet visar att barnen har viss förståelse för vattnets fasövergångar. Slutsatser som går att dra är att barnen tror att vatten kan gå från fast form till flytande form men inte tvärtom.En återkommande tanke som barn har när vatten fryser till is är att man behöver blanda kallt vatten med något och röra runt. Barn tror att temperatur är av betydelse när is smälter eller bildas. De tror också att väderförhållanden är av betydelse för fasomvandlingar. När is smälter tror barnen att vattnet förflyttas och att isen försvinner. Flertalet tankar som barnen i min studie harkan liknas med tidigare forskningsresultat.
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Hur har digitaliseringen i skolan förändrat kemiundervisningen i årskurs 7-9? : En jämförelse mellan forskning och praktikAndersson, Ida January 2018 (has links)
I den reviderade variation av LGR 11 (Läroplan för grundskolan, förskoleklassen ochfritidshemmet 2011) från 2017 lyfts digitaliseringen fram. Skolan är under förändringoch digitala verktyg finns i klassrum. Eleverna förväntas använda dessa och utvecklaförmågor som lyfts fram i LGR 11 och utveckla kunskaper om hur de ska förhålla sigtill ett konstant informationsflöde. Samtidigt använder lärare redan idag många digitalaverktyg i sin undervisning. Med de förändringar som gjorts markerar myndigheter iSverige vikten av att eleverna lär sig navigera och hantera den digitala världen.Frågan som då måste ställas är hur det ser ut i klassrum i Sverige och hurdigitaliseringen har påverkat undervisningen i kemi. När datorn gjorde entréförändrades klassrummet men det tog tid. Idag finns det en mängd olika digitalaverktyg att använda. Genom att gå ut och intervjua lärare skapades en bild avsituationen i det digitala kemiklassrummet. De arbetade med digitala böcker,interaktiva övningar och formativ feedback via delade dokument. Digitaliseringen iskolan speglar den utveckling som samhället har tagit och det är viktigt att alla få följamed i den utvecklingen.Det har även bedrivits forskning inom digitaliseringen i skolan där begrepp som digitalläsning återfinns. Hur har undervisningen hanterats i förhållande till den forskningsom finns och hur lyfter digitaliseringen undervisningen? Genom att göra en jämförelsemellan forskning och praktik skapas en bild av hur det ser ut i skolor men också varmöjligheter för utveckling ligger.
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