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Study on relaxation properties of hydrogels using rheological techniques
Lorenc, Pavel ; Klučáková, Martina (referee) ; Smilek, Jiří (advisor)
Submitted bachelor’s thesis deals with the study of relaxation and time stress of viscoelastic substances (hydrogels) using selected rheological techniques, especially with regard to oscillation tests. Hydrogels with different types of crosslinking were prepared and their properties were compared during the measurement. Agarose hydrogels (physically), alginate hydrogels (physicochemically), polyvinyl alcohol hydrogels (chemically) and hyaluronic acid hydrogels (ionically). In this bachelor's thesis, methods for measuring the relaxation properties of these hydrogels using a rheometer were designed and subsequently applied. We examined the relaxation properties of hydrogels using time-dependent tests that examined changes in amplitude over time. We performed a test that had 3 intervals, in which we monitored the response of hydrogels to the changes by changing the amplitudes of deformation with time. The relaxation properties of these hydrogels were studied, which showed significant differences in the behavior of hydrogels in measurements.By these methods, it was found that the structure of hydrogels and concentrations have an influence on relaxation. From the measured results, it was shown that the best relaxing properties have chemically crosslinked polyvinyl alcohol hydrogel, the lowest ability to relax was shown by physico-chemically crosslinked alginate hydrogel.The results from the measured data were finally compared, assessed and commented on the differences between the individual hydrogels.
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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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Influence of nanoparticles on polymer chains in solution.
Bayer, Adam ; Chamradová, Ivana (referee) ; Jančář, Josef (advisor)
High surface area of used nanoparticles and their comparable size with polymer chains, are the most important characteristics of fillers in the preparation of non-Newtonian suspensions. Such structures at different concentrations have major influence on the rheological behavior of polymer solution in solvent. With increasing volume fraction of nanofiller, there is pseudoplastic or dilatant behavior present in the dissolved elastomers. Diploma thesis studies the influence of the concentration of different elastomers (SBR and SEBS copolymers) and nanofiller (hydrophobic nanosilica) in suspension, of rheological properties.
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Investigation of Polyelectrolytes Interactions with Cationic Aminogroups-containing Amphiphiles
Zeman, Jan ; Běťák, Jiří (referee) ; Chytil, Martin (advisor)
The study deals with interactions of polyelectrolytes polystyrene sulfonate and hyaluronic acid with nitrogenic amphiphilic substances, represented by lysine and albumine. To study the interactions pH-metry, conductance, viscositic and turbidity measurement, DLS and reometry were used. All mixtures of different concentrations were measured and the data were compered with data obtained from measurement of samples with amphiphilic sumstances without polyelectrolytes. Observed interactions occured in the aminoacid concentrations between 0 to 20 mmoldm-3, then the PSS interaction groups were fully bonded by lysine and no more interactions were recognized. The same behaviour were observed in albumine solutions with concentration under 2 gdm-3.
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Characterization of hyaluronan interactions with albumin
Valentová, Kristýna ; Kratochvílová, Romana (referee) ; Chytil, Martin (advisor)
This bachelor thesis focuses on the research of physical interactions between hyaluronic acid and a protein albumin. In order to investigate these interactions following methods were used: pH and conductivity measurement, viscosimetry, turbidimetry and rheometry. The interactions were observed in solutions of fixed albumin concentration 1.0 gdm-3 and varying concentrations of hyaluronic acid from 0.1 to 2.0 gdm-3. Results were compared with a solution of hyaluronic acid without the addition of albumin. The results show that there are interactions between hyaluronic acid and albumin solutions, especially for those containing high molecular weight hyaluronic acid. The interactions exhibited a change in viscosity of solutions. We can see a reduction in viscosity after adding albumin to the reference solutions. The reduction is noticeable even in the low molecular weight HA solutions, but is not so significant.
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Hyaluronan-albumin complexes behavior at physiological conditions.
Šuleková, Nikola ; Kratochvílová, Romana (referee) ; Chytil, Martin (advisor)
This thesis discusses the interactions of low molecular weight and high molecular weight hyaluronic acid (HA) with bovine serum albumin (BSA) in physiological environment. It is based on previous work dealing with HA and amphiphilic substances which are currently widely studied for its potential applications in medicine. Solutions of HA with fixed concentration and albumin of concentration in the range of 0,25 – 20 g/l were prepared at room temperature and at 37°C and examined by rheometry and turbidimetry. It was observed that the maximum absorbance increases with increasing concentration of BSA and does not show variations depending on the temperature of preparation. On the other hand, the turbidity occurs in significant differences between the samples prepared at ambient temperature and at 37°C. Overall, the turbidity increases with the concentration of BSA. Rasing the temperature caused the increase in viscosity of the samples, which was further varied with the concentration of BSA. Mixed solutions of high molecular weight HA and BSA showed the highest turbidity, maximum absorbance and viscosity, while the solutions of BSA showed the lowest values. The results indicate formation of complexes, of which properties are dependent on BSA concentration, the molecular weight of HA, and the temperature of preparation.
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Composite hydrogels
Blechová, Dominika ; Smilek, Jiří (referee) ; Venerová, Tereza (advisor)
The content of this bachelor's thesis is research on the topic of composite hydrogels and subsequent research on the rheological properties of prepared hydrogels from the polysaccharide – Gellan, as well as the determination of the properties of hydrogels with the addition of two types of particles – IPA vesicles and a mixture of hydroxyapatite and calcium sulfate particles obtained by the breakdown of PerOssal pellets (PO particles). Hydrogels are prepared with three different concentrations of Gellan – 1%, 1.5% and 2%. The properties of hydrogels prepared in this way were determined using frequency and mainly amplitude tests. Furthermore, two different methods of applying the sample to the measuring plate of the rheometer were compared. The commonly used method of slicing the sample has been replaced by injection application. The injected samples were measured, the results evaluated and compared with the results of the gels applied by slicing.
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Study on relaxation properties of hydrogels using rheological techniques
Lorenc, Pavel ; Klučáková, Martina (referee) ; Smilek, Jiří (advisor)
Submitted bachelor’s thesis deals with the study of relaxation and time stress of viscoelastic substances (hydrogels) using selected rheological techniques, especially with regard to oscillation tests. Hydrogels with different types of crosslinking were prepared and their properties were compared during the measurement. Agarose hydrogels (physically), alginate hydrogels (physicochemically), polyvinyl alcohol hydrogels (chemically) and hyaluronic acid hydrogels (ionically). In this bachelor's thesis, methods for measuring the relaxation properties of these hydrogels using a rheometer were designed and subsequently applied. We examined the relaxation properties of hydrogels using time-dependent tests that examined changes in amplitude over time. We performed a test that had 3 intervals, in which we monitored the response of hydrogels to the changes by changing the amplitudes of deformation with time. The relaxation properties of these hydrogels were studied, which showed significant differences in the behavior of hydrogels in measurements.By these methods, it was found that the structure of hydrogels and concentrations have an influence on relaxation. From the measured results, it was shown that the best relaxing properties have chemically crosslinked polyvinyl alcohol hydrogel, the lowest ability to relax was shown by physico-chemically crosslinked alginate hydrogel.The results from the measured data were finally compared, assessed and commented on the differences between the individual hydrogels.
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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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Hyaluronan-albumin complexes behavior at physiological conditions.
Šuleková, Nikola ; Kratochvílová, Romana (referee) ; Chytil, Martin (advisor)
This thesis discusses the interactions of low molecular weight and high molecular weight hyaluronic acid (HA) with bovine serum albumin (BSA) in physiological environment. It is based on previous work dealing with HA and amphiphilic substances which are currently widely studied for its potential applications in medicine. Solutions of HA with fixed concentration and albumin of concentration in the range of 0,25 – 20 g/l were prepared at room temperature and at 37°C and examined by rheometry and turbidimetry. It was observed that the maximum absorbance increases with increasing concentration of BSA and does not show variations depending on the temperature of preparation. On the other hand, the turbidity occurs in significant differences between the samples prepared at ambient temperature and at 37°C. Overall, the turbidity increases with the concentration of BSA. Rasing the temperature caused the increase in viscosity of the samples, which was further varied with the concentration of BSA. Mixed solutions of high molecular weight HA and BSA showed the highest turbidity, maximum absorbance and viscosity, while the solutions of BSA showed the lowest values. The results indicate formation of complexes, of which properties are dependent on BSA concentration, the molecular weight of HA, and the temperature of preparation.
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