The diploma thesis deals with preparation of acrylic copolymers via emulsion polymerization technique. Two sets of copolymer samples were prepared within this thesis, n BA/MMA and 2-EHA/MMA copolymers. n-BA/MMA copolymer sample was used for investigation of effect of surfactant concentration as well as effect of addition of acrylic acid to the feed composition. During all the copolymerizations, conversion was observed via solids content evaluation as the reaction progressed. Copolymerization was lead under inert atmosphere at continuous stirring and 80 °C for 4 hours. Glass transition temperature of samples was determined with DSC and Vicat softening point was measured as well. Data acquired from measurements were compared with values calculated with Fox equation which was used for modelling molar ratio of monomers in initial feed.

Refractive index measurements of the Strontium-Barium-Niobate (SBN) crystals show that none of the known second-harmonic-generation scheme (SHG) can be hold responsible for the SHG in SBN. Based on observations of the SHG experiments carried out with several compositions of the crystals in different setup-geometries a new model of second harmonic generaion was developed. The new SHG model, domain-induced second-harmonic generation (DISHG), which considers that the needle-like domain structure of this material plays an active role in the quasi phase matching of the produced second harmonic light has been experimentally proved using two different experiments. The new SHG process in the SBN crystals is a potential light source of cylindrically polarized light. The easy way of obtaining cylindrically polarized light with the SBN crystal broadens the potential applications for this material. The (DISHG) allows to investigate several properties of the ferroelectric domains. Using SHG measurements it was possible to analyze the development of the domain densities for domains of different sizes during the poling of the crystal. SHG measurements allow us to determine the minimum length of the ferroelectric domains. It was shown that this does not depend on the [Sr]/[Ba] ratio and domains are not getting longer after the sample was poled, except for the case of doped SBN. The ferroelectric-paraelectric phase transition has also been investigated. From the inflection point of the nonlinear susceptibility as function of the temperature the phase transition temperature was determined. The non fully-linear dependence of the phase transition temperature as function of the [Sr]/[Ba] ratio can be explained by a system of three different sublattices at the crystallographic positions of Strontium and Barium atoms.

Several SBN-x crystals of different composition have been investigated using the following methods: Optical absorption in the band gap spectral region, optical absorption of the OH-stretch-mode in the near infrared, Raman scattering, pyroelectric and dielectric measurements.The band edge position depends on the crystal composition in a non-linear manner, thus showing band bowing, typical for mixed systems. A new method has been developed to increase the hydrogen content in the bulk. This doping depends on the composition in an almost linear manner. The observed OH stretch mode spectra have been deconvoluted into three sub bands which can be attributed to different sites in the lattice. The composition dependent spectra have been modelled with a few parameters, using different line shapes and both linear and quadratic dependences of the band position.Raman spectra of several crystals of different composition were recorded for four different scattering configurations. Changes for wave numbers below 500 have been found, but could not attributed to particular modes. A prominent feature at about 600 wave numbers was not disturbed by other modes allowing a decomposition and an assigned of this mode to a certain vibration. It was found that the behaviour of this mode is governed by the [Sr]/[Ba] ratio in the pentagonal channel of SBN-x.The ferroelectric relaxor phase-transition of SBN-x has been studied with pyroelectric measurements. From the nonlinear susceptibility as a function of temperature the phase-transition temperature was deduced using the inflection point. The non fully-linear dependence of the phase-transition temperature as a function of the [Sr]/[Ba] ratio can be explained by a system of three different sublattices for the Strontium and Barium atoms.First results obtained with a setup for measuring the dielectric constant confirmed already reported data of other groups.

<p>Smart windows that modulate solar radiation by changing their optical state in response to temperature stimulus are developing as promising solutions towards reducing the energy consumption of buildings. The market adoption of such systems has been slow due to the barriers in scalability, cost, as well as complexity in their integration into existing systems. Aiming these features, we have proposed a retrofit smart window design based on the temperature-responsive polymer Methyl Cellulose (MC). The system utilizes a sustainable, earth abundant and cost-effective cellulose based thermo-responsive material to transform existing windows to a thermally dynamic smart window system. The observed optical change of MC from transparent to opaque state is dependent on temperature and is triggered by the thermodynamic mechanism of reversible coil-globule transition, which results in a stable performance of the proposed device. Its solar modulation ability was studied using ultraviolet-visible- spectroscopy. Effect of MC concentration and various salts on the optical performance were investigated. It was found that the transition temperature the polymer can be tuned by varying MC concentration and by adding salts to the system. The tunability of transition temperature is a function of the concentration of salt and the type of anion in the salt. It was observed that the transition temperature of the window can be tuned between to , allowing a wide range of control over switching temperature. Controllable LCST, low freezing point, sustainable base material, scalable production, low cost, retrofit system makes them ideal candidates for smart window applications. </p>

<p dir="ltr">Computational materials science has emerged as a powerful technique to discover and develop new materials in past decades, primarily because accurate computational modeling can act as guidance before performing experiments that are expensive and time-consuming. However, modeling material behaviors across different scales of length and time poses a challenge, accentuating the importance of choosing appropriate levels of approximations and theories. First principles calculations based on density functional theory (DFT) are essential to predict the electronic structure of periodic crystalline systems. We will discuss a prediction of chemical doping induced metal-to-insulator transition (MIT) of transition metal perovskites owing to the variation of the electronic occupation. Nevertheless, electronic structure predictions based on DFT are not without limitation as it fails when treating strongly correlated electronic system due to the over-delocalization of valence electrons. In principle, adding on-site Hubbard U corrects this error with a low computational cost. Using an example of a two-dimensional rare-earth MXene, we demonstrate the essence of choosing the appropriate U value self-consistently for the prediction of electronic and magnetic configurations. Furthermore, molecular dynamics (MD) can be employed to study the dynamic evolution of complex condensed systems with thousands to millions of atoms at the atomistic and molecular levels. Carbon fiber manufacturing is an established industry, though the fiber produced achieves only 10% of its theoretical tensile strength. Therefore, optimizing the carbon fiber processing is a pressing topic. To achieve this, we study two steps, spinning and stabilization, of polyacrylonitrile (PAN)-based fiber fabrication at the molecular level using MD. We will discuss the realistic molecular structure of the spun PAN and the properties affected by its structural heterogeneity. Moreover, for the following step, we develop a PAN stabilization simulator, an automated workflow that addresses the underlying chemistry and the molecular-level structure-property relationship, often inaccessible through experiments.</p>

Compression of coated pellets is a practical alternative to capsule filling. The current practice is to add cushioning agents to minimize the stress on the coated pellets. Cushioning agents however add bulkiness and reduce the overall drug loading capacity. In this study, we investigated the performance of compressed coated pellets with no cushioning agent to evaluate the feasibility of predicting the coat behaviour using thermo-mechanical and rheological analysis techniques. Different coating formulations were made of ethyl cellulose (EC) as a coating polymer and two different kinds of additives were incorporated into the polymeric coating solution. Triethyl Citrate (TEC) and Polyethylene glycol 400(PEG400) were used as plasticizers at different levels to the coating formulations (10%, 20%, 30%). Thermal, mechanical and rheological measurements of the coating film formulations were achieved to investigate the effect of plasticizers. Thermal gravimetric analysis results (TGA) showed higher residual moisture content in films plasticised with PEG 400 compared to their TEC counterparts. Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and Parallel Plate Shear Rheometer (PPSR) were used to study the influence of the level and type of plasticisers incorporated in coating film formulation on the performance of the coating film. In this study, both DSC and DMA were used to investigate the Tg for each film coating formulation in order to evaluate the effect of the additives. In general DMA results for the Tg value of the films were always higher by 10-20% than those measured by the DSC. Furthermore, clamp size and the frequency of the oscillation have an influence on the evaluation of Tg. Complex viscosity for different coating film formulations revealed that the shear hinning gradient changes with temperature and plasticiser type and concentration. The value of complex viscosity from DMA and PPSR exhibits power law behaviour. The rheological moduli were indirectly affected by the level of plasticiser. There was a discrepancy between the complex viscosity results obtained from both DMA and PPSR at similar temperature but they follow the same trend. The non plasticized polymer showed a 10 time higher complex viscosity values when measured by DMA over that measured by PPSR. The difference was smaller in plasticized films but it was not consistent. Therefore a consistent coefficient to correlate the DMA and PPSR couldn’t be accurately determined Coated pellets were compressed and key process parameters were evaluated. The obtained results revealed that the coating thickness has a significant effect on the release profile of the final products. It was found that by increasing the coating film thickness, the percentage released decreased. Also the compression force has lower influence on the drug release profile, while the dwell time has very low effect on the percentage release from the final products. Optimum release profile was obtained at a coating level of 5.5% w/w and a compression force of 4700N In conclusion, the elasticity of the plasticised EC films in this study meant that the internal stress is not dissipated during compression and the dwell time range that was used in this experiment. Increasing the thickness therefore was necessary to enhance the strength of the film and avoid cracking. The mechanical and rheological profiling was helpful therefore to understand the behaviour of the coated pellets and predict the film properties at various steps of the process of coating and compression (i.e., various shear rate regimes). Experimental design approach to studying the key process and formulation parameters helped identify the optimum values for the process.

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