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Time-temperature superposition principle used for study of rheological properties of polymer materials
Kadlec, Martin ; Jarábková, Sabína (referee) ; Smilek, Jiří (advisor)
This bachelor thesis provides a study of the “time-temperature superposition” principle and its applicability to hydrogels. According to current research, honey was chosen due to its simple viscoelastic properties (Newtonian liquid) as a suitable material for optimalization procedure. The knowledge obtained during optimization was further applied to real hydrogel materials, namely the agarose gel was selected as an example of thermoreversible hydrogel, as well as the hyaluronan and dextran gels as examples of hydrogels formed by the interaction of the polyelectrolyte with the opposite charged surfactant. By using the “time-temperature superposition” principle, a considerable increase in the range of the observed oscillation frequencies was achieved for all chosen samples, which led to gain of information about storage and loss or complex modulus, which could not be achieved by classical oscillatory test. Although master curves were generated for all the samples examined, curves for storage and loss modulus could be created separately only for hydrogels formed by the interaction of the polyelectrolyte with the opposite charged surfactant. For this reason, this group of hydrogels appears to be more suitable materials for the application of the “time-temperature superposition” principle.
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Mixed lipids and their interaction with biopolymers
Cigánková, Hana ; Smilek, Jiří (referee) ; Mravec, Filip (advisor)
This thesis focuses on the study of interactions between hyaluronan and lipid DOTAP and its mixtures with DPPC in water. First, the aggregation behavior of the lipid itself and its mixtures was measured, afterwards the influence of hyaluronan in different concentration was studied. Further the fluorescence anisotropy of fluorescence probe DPH in these mixtures and influence of cholesterol was measured. These properties were investigated by fluorescence spectoscopy using pyrene and DPH as fluorescence probes. The measurements revealed that the addition of hyaluronan has observable influence on the aggregation behavior of the lipid DOTAP and its mixtures with DPPC and that cholesterol influences liposomes fluidity.
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Diffusivity of humic hydrogels
Král, Jan ; Smilek, Jiří (referee) ; Klučáková, Martina (advisor)
Presented diploma thesis focuses on the study of diffusion of cupric ions in humic acid gels. A total of fifth different standards of humic acids and one sample humic acid prepared from same source as in bachelor's thesis, on which this thesis continues, were used for preparation solutions of humic acids. Thereafter, these solutions were used for preparation of agarose hydrogels, which were necessary in following diffusion experiments. The objective of the work was to compare transport properties of humic standards between themselves and then compare standards with humic acid prepared from same source as in bachelor's thesis. Measure, which was used to determine the transport properties, was comparison of effective diffusion coefficients. Method of instantaneous planar source diffusion was used to compare them. This method was based monitoring temporal evolution of diffusion profiles of cupric ions in humic hydrogels. Copper ions were selected as diffusing medium because of their high affinity and strong bonds to humic acids.
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Preparation and characterization of hydrogels based on cationic biopolymer
Tesařová, Barbora ; Mravec, Filip (referee) ; Smilek, Jiří (advisor)
Presented thesis deals with the preparation and characterization of hydrogels based on positively-charged biopolymer and negatively-charged tenside. As an appropriate representative of positively-charged polymer was chosen chitosan, because of his biocompatibility and biodegrability, and N,N,N-trimethylchitosan, which was synthetised from chitosan in this diploma thesis. The final product of synthesis was characterised by SEC-MALS, elemental analysis, infrared spectroscopy and nuclear magnetic rezonation. Interactions between these polymers and representatives of negatively-charged tensides, which are sodium dodecylsuphate and sodium tetradecylsulphate, were investigated. The main method used in this thesis was rheology, through it were investigated prepared hydrogels based on chitosan and tensides and also prepared microgels based on N,N,N-trimethylchitosan and tensides. The interactions between polymers and tensides have been proved.
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The influence of biochar on physico-chemical properties of soil
Polášková, Nikola ; Sedláček, Petr (referee) ; Smilek, Jiří (advisor)
This thesis is focused on assessment of the influence of biochar on the soil physico-chemical properties (particle density, dry density, porosity, water retention capacity and maximum water holding capacity, oxidizable carbon content, total nitrogen content, phosphorus, potassium and magnesium content). The selected and examined soil types were: cambisol, fluvisol, chernozem and regosol. There were two types of biochar used for analysis – NovoTerra and Sonnenerde. Soil samples were dried to constant weight and adjusted to grain-size fraction under 2 mm, respectively 0,25 mm. The oxidizable carbon content was measured by oxidation using a mixture of potassium dichromate and sulphuric acid (Walkley-Black method), the total nitrogen content was measured by kjeldahlization and P, K and Mg content was measured using Mehlich 3 extraction and ICP-OES spectrometer. The results show that biochar has a significant influence on soil characteristics depending on the type of biochar and soil we use for biochar application. This thesis can be used to clarify the complex issues in terms of soil in Czech Republic or it can be used by farmers considering using biochar as a soil additive with the intention to increase productivity and fertility of soil.
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Use of microcalorimetry in the study of hydration of biopolymers
Bola, Tomáš ; Smilek, Jiří (referee) ; Krouská, Jitka (advisor)
This master thesis deals with the using of microcalorimetry in the study of hydration of biopolymers. Lactose has been selected together with the other biopolymers although it is not among biopolymers but disaccharides. Selected biopolymers are alginate, dextrane, chitosan and hyaluronan of two molecular weights. Lactose has been selected for these purposes mainly because it is a model example to determine whether or not the reaction to moisture between the other samples and the saturated salt solution occurs. The biopolymer hydration study, as opposed to the commonly used perfusion calorimetry method using the possibility of measuring with adjustable moisture has been used an isothermal microcalorimetry method where at two constant temperatures the reaction of the sample to the different moisture released by the saturated salt solution was monitored.
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Biodegradation of polyesters and other polymers in soil and compost
Papala, František ; Smilek, Jiří (referee) ; Obruča, Stanislav (advisor)
This diploma thesis studies the biodegradation of polyhydroxybutyrate (PHB) and polylactic acid (PLA) within soil and compost environments. The experimental part of this work is concerned with the differences in degradation across environments and the effects of degraded polymers on the environment itself. Experiments revealed that higher temperature and potentially also higher humidity substantially affect the rate of biodegradation. A significant degradation of all the polymers was observed in the compost medium, while polymers within the soil medium did not demonstrate any visible change nor change in mass after the 8th week of experiment. Even though SEM images revealed slow microbial degradation of soil PHB, this was not seen in any of the soil-incubated PLA samples. This might indicate primarily abiotic mechanism of PLA degradation. Germination and grow tests, which used the prepared polymer-enriched compost as a substrate and fertilizer, respectively, did not in most cases reveal any significant differences between individual plants across substrates. This seems to imply that neither the examined polymers nor their degradation products generated during composting are phytotoxic.
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Preparation and characterization of hybrid hydrogels matrix
Magera, Lukáš ; Kalina, Michal (referee) ; Smilek, Jiří (advisor)
Submitted bachelor’s thesis aims for preparation and subsequent optimisation of hybrid hydrogels, which represent material with high application potential because of their unique properties. Hybrid hydrogels have extraordinary mechanical resistance and other beneficial properties (e.g. transportation) due to their unique hybrid network structure, strong interpenetrating network entanglement and efficient energy dissipation system. This work engages in chemically-physically crosslinked hybrid gel, namely the combination of alginate-polyacrylamide. The hybrid hydrogel was formed and then underwent the tests of drying and swelling. The main purpose of the experimental part was to determine viscoelastic properties of hybrid hydrogels using standard oscillation tests. Swelling tests showed that the hybrid network containing limitedly swelling alginate gel reaches lower degree of swelling than the single unlimitedly swelling polyacrylamide gel. Viscoelastic tests unveiled an influence on the mechanical properties by value augmentation of the hybrid gel´s storage modulus in comparison with the reference alginate hydrogel. Hybrid hydrogel reported an increase in the linear viscoelastic area compared to the reference polyacrylamide gel, whose hybrid structure prevents from creating microcracks, that caused earlier rupture of the reference polyacrylamide gel.
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Time evolution of rheological parameters of slag activated with various activators
Pazour, Miroslav ; Smilek, Jiří (referee) ; Bílek, Vlastimil (advisor)
Tato diplomová práce se zabývá aktuálními poznatky, společně s optimalizací oscilačních měření pomocí hybridního reometru, ale hlavně pozorováním změn reologických parametrů v čase past mleté granulované vysokopecní strusky aktivované různými aktivačními roztoky s koncentrací alkálií M: 4 and 7.5 moldm. Výsledky byly pro diskuzi podpořeny výstupy z Vicatovy metody a izotermické kalorimetrie. Nejprve bylo zjištěno, že limit lineární viskoelastické oblasti se zmenšuje v čase. Dále bylo pozorováno, že v time sweep testech vykazovala struska aktivovaná křemičitany nejnižší hodnoty komplexního modulu a struska aktivovaná hydroxidy o koncentraci 4 moldm nejvyšší hodnoty a ostatní pasty vykazovaly hodnoty mezi těmito dvěma extrémy a měly mezi sebou porovnatelné hodnoty. Podobný trend byl pozorován u vývoje kritické meze oscilačního napětí, získaného z amplitude sweep testů (přerušovaně a nepřerušovaně). Oba výše zmíněné parametry, komplexní modul a mez napětí, se vyvíjely v čase. Výsledky všech testů jasně ukázaly, že povrchová chemie hraje roli ve výsledném reologickém chování. Odsud, povaha a koncentrace aktivátoru ovlivňují reologické vlastnosti skrze efekty Na a K iontů, stejně tak skrze koncentraci, která má dopad na elektickou dvojnou vrstvu. Reologické chování může být také ovlivněno dalšími faktory, např. viskozitou aktivačního roztoku a celkovou kinetikou hydratačního procesu.
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The behavior of superabsorbent polymers in artificial soils
Männlová, Adriana ; Smilek, Jiří (referee) ; Kratochvílová, Romana (advisor)
This bachelor thesis deals with the study of superabsorbent polymers for environmental and agricultural applications. Generally thessis preparations are to perform the funciton of irrigation ,so that thanks to its unique properties , can absorb water in tha rainy season and keep it arend the root system as long as possible. Superabsorbent polymers can also perform the fiction of fertilizer carries and thus ensure its gradual release. These gel structures were subjected to testing of their swelling in environments with different ionic strenght. Subsequently, in the long term monitored thein ability to trap water in the soil environment model.
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