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Chemical modifications of hydrogels from natural polysaccharide
Poštulková, Hana ; Žídek, Jan (oponent) ; Vojtová, Lucy (vedoucí práce)
Chemical structure, use and chemical and physical properties of natural polysaccharide gum karaya (Sterculia urens) were summarized in theoretical part of this work. The general goal of the diploma work was modification of original insoluble gum karaya under alkali condition to prepare water soluble sample for further applications. Insolubility of gum karaya is caused by presence of acetyl groups and multivalent ions in the structure of polysaccharide. Optimized conditions for modification process were investigated. Sodium, potassium or ammonium hydroxide, 1 minute to 24 hours of treatment and 0.1 - 3% solution of original gum karaya were used for optimizing the modification process. Original (OGK) and modified (MGK) samples were studied by FTIR to investigate chemical composition. Modified samples A2, B1-7, C1-8 and E1-2 were considered as fully deacetylated because of absence of band at 1725 cm-1 which represents acetyl group. Absence of acetyl groups after modification was also proved by 13C CP MAS NMR. Amorphous character of original gum karaya was determined by XRD. TGA was used to evaluate amount of moisture and thermal stability of original and modified samples. Thermal stability of OGK was higher (280 °C) than of modified samples. Thermal stability of MGK was affected by reaction parameters. Thermal changes in polysaccharide chains were studied by DSC but any significant differences between OGK and MGK were not observed. Mineral composition of original and modified samples was investigated by ICP OES and presence of calcium, potassium and magnesium ions in OGK was confirmed. Molecular weight of modified samples was evaluated by GPC and was approximately 8 million g·mol-1. Rheological measurement for determination of linear viscoelastic region was determined. Effect of NaCl on viscosity of original gum karaya was performed. Viscosity of OGK decreased with higher amount of NaCl. Lower viscosity of OGK is connected with exchange of Ca2+ for Na+ ions and release of the physically bonded structure resulting in higher solubility of OGK in water.
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The effect of biopolymers on adhesive and rheological properties of calcium phosphate bone cements
Scholz, David ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
This thesis deals with bone cement composed of tricalcium phosphate and thermosensitive copolymer. The main aim was to improve especially the adhesive properties of the cement by adding polysaccharide. The theoretical part of the thesis deals with the characterization of bone cements and their application and also a description of polymeric additives used in bone cements mainly focused on polysaccharides. In the experimental part, the prepared cements were characterized using rheology, powder X-ray diffraction and static mechanical tests on the cured cement alone and glued bones. Rheology was used to measure the setting time of the cements as a function of time and temperature. Furthermore, rheology was also intended to measure the adhesive properties of copolymer solutions, but this was not possible due to the nonreproducible results caused by inhomogeneity of the copolymer solutions with polysaccharide. Powder X-ray diffraction was used to measure the effect of polysaccharide on the conversion of tricalcium phosphate to calcium deficient hydroxyapatite. It was found out that polysaccharide does not significantly affect the conversion of tricalcium phosphate. Static mechanical tests were used to measure maximal compressive strength for the cured cement samples and also to measure the adhesion strength of glued bone samples. Cured samples with low polysaccharide concentration showed higher compressive strength compared to control samples. Inconclusive results were obtained during testing of the bone samples due to the complexity of the measurement. In particular, it concerns the preparation of bone samples and their gluing with bone cement.
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Chemical modifications of hydrogels from natural polysaccharide
Poštulková, Hana ; Žídek, Jan (oponent) ; Vojtová, Lucy (vedoucí práce)
Chemical structure, use and chemical and physical properties of natural polysaccharide gum karaya (Sterculia urens) were summarized in theoretical part of this work. The general goal of the diploma work was modification of original insoluble gum karaya under alkali condition to prepare water soluble sample for further applications. Insolubility of gum karaya is caused by presence of acetyl groups and multivalent ions in the structure of polysaccharide. Optimized conditions for modification process were investigated. Sodium, potassium or ammonium hydroxide, 1 minute to 24 hours of treatment and 0.1 - 3% solution of original gum karaya were used for optimizing the modification process. Original (OGK) and modified (MGK) samples were studied by FTIR to investigate chemical composition. Modified samples A2, B1-7, C1-8 and E1-2 were considered as fully deacetylated because of absence of band at 1725 cm-1 which represents acetyl group. Absence of acetyl groups after modification was also proved by 13C CP MAS NMR. Amorphous character of original gum karaya was determined by XRD. TGA was used to evaluate amount of moisture and thermal stability of original and modified samples. Thermal stability of OGK was higher (280 °C) than of modified samples. Thermal stability of MGK was affected by reaction parameters. Thermal changes in polysaccharide chains were studied by DSC but any significant differences between OGK and MGK were not observed. Mineral composition of original and modified samples was investigated by ICP OES and presence of calcium, potassium and magnesium ions in OGK was confirmed. Molecular weight of modified samples was evaluated by GPC and was approximately 8 million g·mol-1. Rheological measurement for determination of linear viscoelastic region was determined. Effect of NaCl on viscosity of original gum karaya was performed. Viscosity of OGK decreased with higher amount of NaCl. Lower viscosity of OGK is connected with exchange of Ca2+ for Na+ ions and release of the physically bonded structure resulting in higher solubility of OGK in water.
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