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Preparation and characterization of magnetorheological suspensions with high sedimentation stability
Oharek, Lukáš ; Krouská, Jitka (referee) ; Smilek, Jiří (advisor)
The introduced diploma thesis focuses on the preparation of magnetorheological suspensions with high sedimentation stability. The theoretical part generally describes these suspensions and their properties, it also focuses on the possibilities of improving sedimentation stability, for example by modifying the surface of the particles or adding additives. A research based on the topic of preparation of sedimentation stable magnetorheological suspensions was also carried out. The experimental part focuses on two types of magnetorheological suspensions. The first type of suspension consisted of a water-in-oil emulsion and carbonyl iron particles that were modified by chemisorption of the surfactant Tween 80. Another type of suspension contained thixotropic organoclay along with untreated iron particles. In both types of magnetorheological suspensions, the process of their preparation was optimized, together with the composition of carrier fluids for the preparation of the most sedimentation-stable magnetorheological suspension. The measurement of sedimentation stability by a dispersion analyser confirmed the positive effect of particle modification and the addition of thixotropic agent on the sedimentation stability of suspensions.
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Characterization of medical biopolymers by ultrasound spectroscopy
Jugl, Adam ; Krouská, Jitka (referee) ; Hurčíková, Andrea (advisor)
Using high resolution ultrasonic spectroscopy has been investigated hyaluron solutions of various molecules weights depending on their concentration and solution temperature. Furhermore, the influence of ionic strenght on the properties of solutions by dissolving hyaluronan in 0.15 M aqueous solution of sodium chloride. For comparison the properties of the hyaluronan solutions were compared with aqueous solutions of carrageenan. It was found that hyaluronan in solution behaves the same, regardless of the weight, temperature and concentration.
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Hyaluronan hydrogels for medical applications
Janča, David ; Krouská, Jitka (referee) ; Venerová, Tereza (advisor)
This work studies properties of hydrogels prepared by the interaction of polyelectrolyte hyaluronate with cationic surfactant cetyltrimethylammonium bromide (CTAB) in a model physiological solution of 0,15 M NaCl. Effects of different pH and final pH of different samples of hydrogels were studied. Furthermore, stability of hydrogels was observed by fluorescence spectroscopy, where pyrene was used as a fluorescence probe, and isothermal microcalorimetry. It was found that low temperature disrupts gel integrity and it is not recommended to expose hydrogels to other than a neutral pH.
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Study on interaction of humic substances with surface active agents
Bělušová, Anna ; Krouská, Jitka (referee) ; Smilek, Jiří (advisor)
This bachelor thesis deals with the study of interactions between humic acids (HK), as the main component of soil organic matter, and model pollutants in the form of surfactants through unconventional and original combination of dialysis and diffusion techniques. Since dialysis techniques are rarely used for the interaction of humic substances with surfactants study, it was necessary to optimize methods for determining of ionic surfactants (cationic Septonex and anionic sodium dodecylsulfate were selected as representatives) prior to begining of own experiments, using a method based on the color ion pair creation between a surfactant and a counter-charged dye, followed by this pair extraction into an organic solvent. Diffusion cell dialysis experiments were performed with cationic surfactant Septonex, which was expected to interact positively with humic acids relative to its charge. As humic acids representatives, the standards of these substances provided by the International Society for Humic Substances (IHSS) were selected, namely humic acids (IHSS HK) isolated from Leonardite (1S104H). One of this bachelor thesis aims was to verify the effect of carboxylic functional acids on reactivity and barrier abilities of humic acids. For this reason, these standards have been modified by the selective methylation of carboxyl groups which no longer participate in the interaction with surfactants. Already from the first experiments there was a noticeable decrease in the concentration of Septonex over time – it means its transition through the dialysis membrane to humic acids, which indicates a positive affinity of humic acids to Septonex. The extent of these interactions was assessed through the apparent interactions parameter app through which the assumption that IHSS HK reacted with Septonex more than their methylated form of MIHSS HK was verified.
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Preparation and Characterisation of Polyelectrolyte Complexes in the System Dextran-Surfactant
Klímová, Eliška ; Krouská, Jitka (referee) ; Kalina, Michal (advisor)
This bachelor thesis deals with the study on preparation and characterization of the polyelectrolyte complex formation in the dextran-surfactant system. The aim of the thesis was the investigation of the influence of the ionic strenght on the formation of the interactions in the studied system. For these purposes, components having opposite charges (DEAE-dextran hydrochloride and anion-active sodium dodecyl sulphate) were selected. For individual measurements mainly the methods of light scattering, dynamic and electrophoretic light scattering in particular, have been used. In the thesis have been studied interactions and aggregation concentrations of individual components having the potential to form polyelectrolyte complexes. It was verified in all the studied samples, by measuring the intensity of scattered light and the size of Z-diameter of particles, that the increase in sizes of particles is caused by the formation of these complexes. There were also measured additional characteristicts of the system such as pH or conductivity. Their dependences provide comprehensive view on the formation of complexes in studied system and can be utilized for other measurements and possible future applications, especially for purposes in medical applications.
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Study of thermal properties of phase change materials
Křivánková, Kateřina ; Krouská, Jitka (referee) ; Zmeškal, Oldřich (advisor)
The diploma thesis studies the thermal properties of materials, heat storage based on phase transformation. The aim of this study was to measure the thermal properties of materials using a heat accumulation phase transformation, particularly a commercial material available from the Phase Change Material Products Ltd. under the name PlusICE A118. Such materials are referred to as PCM (from Eng. Phase Change Material), and are used for instance as heat insulators in construction. First described the phase transformation of substances in general, then was defined accumulation of thermal energy. We have also described methods for determining the temperature (thermal analysis, stationary and transietní methods). Finally defined thermophysical parameters (thermal capacity, thermal conductivity, thermal conductivity), which were determined transient step method.
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Interaction of trimethylchitosan with Niaproof surfactant
Zbořilová, Hana ; Krouská, Jitka (referee) ; Mravec, Filip (advisor)
This thesis is focused on the study of interaction of the polycation N,N,N-trimethylchitosan (TMC) with the anionic surfactant Niaproof® 4 in water and physiological saline solution. Due to the commercial unavailability of N,N,N-trimethylchitosan, the polymer was first synthesized from chitosan, followed by NMR and FTIR characterization. Before the study of the system polycation–anionic surfactant itself, the behavior of the anionic surfactant Niaproof® 4 in aqueous solution and physiological saline solution was explored. The micellization of the surfactant Niaproof® 4 and the aggregation of TMC–Niaproof® 4 system were observed by fluorescence spectroscopy using the fluorescence probe pyrene. Values of critical micelle and critical aggregation concentration were determined on the basis of measurements. It was confirmed that presence of the sodium chloride supports the micellization by increasing the ionic strength of the solution, which leads to decrease of CMC in physiological saline solution. The interaction of TMC–Niaproof® 4 occurs at lower concentration then CMC in both aqueous and physiological environments. Phase separation occurs at higher concentrations of the surfactant leading to stabilization of the system.
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Preparation and application of physical hyaluronan gel
Kovářová, Lenka ; Krouská, Jitka (referee) ; Venerová, Tereza (advisor)
Bachelor's work is concerning by research in physical hyaluronan gel area. Research is focusing on its preparation, especially by interaction of hyaluronan (HyA) solution with opposite charged surfactant in physiological solution (0,15 M NaCl). In the first part of work I found out influence of molecular weight, concentration of original hyaluronan solution and the ratio of binding sites on hyaluronan chain and surfactant on amount of solids in gel, expressed in percent. Finally we can say, that this value is not influenced by molecular weight of HyA neither relation of binding sides. On the other side, concentration of original HyA solution has significant influence on amount of solids in gel. There was also researched process of gel swelling, where was set amount of water (in percent) able to take dried gel back. Analogical conclusion has been reached like amount of solids in gel. In other part were researched influence of hyaluronan molecular weight and the ratio of binding sites on hyaluronan chain and surfactant on formation of excimers and spectrum change by fluorescence spectroscopy. Pyrene, 1,3-bis(pyren-1-yl)propane (P3P) and prodan were used as fluorescence probes. Excimer emission showed at P3P, while there was no growth of intensity at 470 nm for pyrene. It was found that molecular weight does not affect the value of the ratio of excimer and monomer probe P3P, or the ratio of the first and third peaks of pyrene. The ratio of binding sites HyA and surfactant influence only relation of excimer to monomer (P3P probe), while influence to relation 1:3 hasn't been noticed for pyrene. I have compared spectrum of developed gel for prodan probe, relevant solid and swelled gel by return. It also served for drying and swelling process visualisation.
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Fluorescence probes in investigation of associative colloid domains.
Mischingerová, Monika ; Krouská, Jitka (referee) ; Mravec, Filip (advisor)
The aim of this thesis was to determine how the concentration of the fluorescent probe (pyrene) affects the critical micelle concentration. In this thesis were used all types of surfactants (anionic, cationic and nonionic). As representatives of the anionic surfactants were chosen sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfate (SDBS), as the cationic surfactant was chosen cetyltrimethylamonium bromide (CTAB) and as the nonionic polyoxyethylene(9.5)octylphenol (Triton X–100). The critical micelle concentration of these surfactants were measured with a pyrene at three different concentrations. All data obtained by fluorescence spectroscopy were fitted by a Boltzmann-type sigmoid. It was found out that in the case of the anionic surfactants there is some correlation between the critical micelle concentration of the surfactant and the concentration of the fluorescent probe. In both cases (SDS, SDBS) the value of the critical micelle concentration increased with increasing concentration of the fluorescent probe. For the other surfactants (cationic and nonionic) was observed no change in the critical micelle concentration values depending on the concentration of pyrene.
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