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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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Fluorescence probes to study the properties of hydrogel systems
Máčala, Jakub ; Venerová, Tereza (referee) ; Mravec, Filip (advisor)
This bachelors thesis is focused on possibility of selected fluorescent probes for study of properties of hydrogel systems. Chosen probes are Prodan for polarity study, HPTS for measurement of pH of the probe environment and platinum complex [2,6-Bis(2-pyridyl)fenyl-C,N,N]chloroplatinum(II) for its unique fluorescence properties and potential of energy transfer studies in hydrogel systems. Spectral properties of fluorophores were defined in selected set of solvents with different polarity with steady state fluorescence spectroscopy method. Properties of HPTS probe were also tested in buffers with different pH. Subsequently, hydrogels based on hyaluronan-septonex and dextran-SDS with incorporated fluorescence probes were prepared. Steady state fluorescence measurement of fluorophores from hydrogel were made using fluorimeter optical fibres. It was found, that probes Prodan and HPTS are suitable for study of polarity and pH of hydrogels and probably they will be able to be used for study of hydrogel with other techniques, like fluorescence microscopy, however platinum complex is, due to the low fluorescence intensity and possible quenching by polar water environment, probably not suitable for other measurements.
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Transport properties of dextran-based hydrogel systems
Vyroubal, David ; Kalina, Michal (referee) ; Klučáková, Martina (advisor)
This bachelor thesis is focused on study of transport properties of dextran-based hydrogel systems. The aim of this work is to determine their ability to absorb and release substances. Nile red was used as a probe to examine the transport properties of these systems. All hydrogels were prepared by the so-called wet way. At first stock solutions of dextran and surfactants were prepared and subsequently mixed to form a hydrogel. Nile red was dissolved in the surfactant stock solution and colored gels were formed upon mixing with dextran stock solution. Several types of gels were thus formed which differ in the concentration of the surfactant and nile red used. Supernatants were spectrophotometrically measured at various time intervals. For study of transport properties in multiple surroundings, the original supernatant was replaced after hydrogel preparation with a surfactant solution or physiological saline solution.
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The intrecations of dextran with surfactant SDS
Marčanová, Milada ; Kalina, Michal (referee) ; Hurčíková, Andrea (advisor)
Before the itself of characterization interactions of dextran with surfactant SDS, there were investigated properties of dextran solution in water and in sodium chloride. At first it was measured by densitometer, where their density and ultrasonic velocity was investigated, depending on concentration and temperature. The ultrasonic velocity was further measured by high resolution ultrasonic spectroscopy. Subsequently the interactions of dextran with surfactant SDS was examined to determine the critical aggregation and critical micelle concentration.
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Studying the quality of hydrophobic domains in the phase separated hydrogels
Burešová, Natálie ; Pekař, Miloslav (referee) ; Mravec, Filip (advisor)
The thesis deals with the study of hydrophobic domains in phase separated hydrogels. Two types of polyelectrolytes (hyaluronan, dextran) and oppositely charged surfactants (carbethopendecinium bromide, sodium dodecylsulphate ) are used. Phase separated hydrogels are formed by electrostatic interactions. The target of the thesis is to study the polarity of environment in phase separated hydrogeles by fluorescence spectroscopy. Fluorescence measurements is performed by using pyrene, Nile red and laurdane as fluorescence probes. All probes are sensitive to the polarity of the environment. The results showed that probes can be expected in the polar environment of hydrogels.
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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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Hydration of biopolymers
Šméralová, Ester ; Smilková, Marcela (referee) ; Klučáková, Martina (advisor)
Presented bachelor's thesis focuses on the study of hydration of selected biopolymers – humic acids, chitosan, hyaluronic acid (low molecular weight and high molecular weight) and dextran. Thermogravimetric analysis TGA is used t determine the original moisture content of the samples. Two calorimetric methods were used for subsequent observations of changes in their chemical and mechanical properties in the presence of water – differential scanning calorimetry DSC and perfusion calorimetry.
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The influence of enzymes applied on processed sugar beet bulbs on the quality of saturated juice
Langrová, Petra ; Pulkrábek, Josef (advisor) ; Ilona, Ilona (referee)
The thesis focuses on the determination of dextran presence and its potential amount in sugar made semi-products. Dextran is a polysaccharide which is created on a sugar beet tuber due to inappropriate storing, because of low temperatures or wound of beet tissue, which is subsequently prone to infections caused by Leuconostoc mesenteroides microorganism. The infection results in creation of polysaccharides and other secondary products which have a negative influence on technological processing of beet. Levan and dextran create the highest amount of these polysaccharides in sugar beet. They significantly increase the viscosity of sugar juice. It is subsequently seen on crystallization of calcium carbonate during the second saturation and this causes the deterioration of filterability. In case of dextran or other polysaccharides presence other problems arise in the technological process of sugar production. For its elimination enzymatic hydrolysis is used with the aid of dextranase or alfa amylase. This element splits dextran polysaccharide into smaller oligosaccharids which are not caught in filtration device and therefore do not cause reduction in production capacity. Commercially accessible dextranase; however, is financially demanding so that there are researches trying to find more economical ways. This diploma thesis evaluates the presence of dextran in extracted juice by means of ICUMSA GS8-19 (year 2009). The method evaluates the presence of dextran in diffused, heavy and II. saturated juice. The research was focused on determination of alkalinity, pH, sedimentation and filtration coefficient, polarization, sugar content and purity. The aim of this thesis is to evaluate the correlation between recorded numbers and the application of the two enzymes which are used for removal of these problems. After completion of the experiment and evaluation of measured results in operating laboratory of sugar factory Tereos TTD Dobrovice, connection among laboratory measured data was not proved. Our recorded data did not prove reciprocal relation. The only proved connection was about number of rinsed filters (per day) after II. saturation and amount of used enzymes. The amount of enzymes influences how many times per day filters must be rinsed in order to get rid of deposit. In case of high amount of dextran, filters started to be clogged by impervious layer of molecules and in case that enzymatic way was not used for elimination of this saccharide, the only solution was frequent filters rinsing or reduction in working capacity connected to subsequent prolongation of processing campaign.
Further, we proved the efficiency of alfa amylase which was used during beet processing (after New Year). This enzyme had the same impact on elimination of polysaccharides and clearance of filters. It is to say that in following campaigns it is possible to substitute financially demanding enzyme for cheaper alfa amylase.
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Comparative study of interaction between surfactant and hyaluronan and different polyelectrolytes.
Stiborský, Filip ; Pravda,, Martin (referee) ; Pekař, Miloslav (advisor)
In this diploma thesis, the interactions between polyelectrolyte and surfactant at low and also at high concentration were studied. There was used pyrene as fluorescent probe during the fluorescence spectroscopy measurement, a cationic surfactant cetyltrimethylammonium bromide and as a main polyelectolyte has been chosen sodium polystyrene sulfonate at 1 MDa molecular size. In the medium containing 0.15 M NaCl we could observed a creation of the complexes – precipitates in the surrounding of CMC concentration and behind of this concentration. In the mixtures containing sodium polystyrene sulfonate and hyaluronan together, there was stronger tend to keep aggregation properties of sodium polystyrene sulfonate during difference concentration ratios. Beyond CMC concentration, hyaluronan starts to influence the aggregation properties of the system as well.
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