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Polyhydroxybutyrate modification by grafting of functional groups
Melčová, Veronika ; Tocháček, Jiří (referee) ; Přikryl, Radek (advisor)
Presented bachelor thesis deals with a characterization of the effect of chemical grafting on thermal and mechanical properties of poly(3-hydroxybutyrate). Two grafting methods were chosen, chlorination and fluorination of PHB. The aim of the theoretical part of the work was to create a complete literature review containing basic information about polyhydroxybutyrate and the latest scientific evidence about possibilities of chemical modification of this polymer. The experimental part describes the chemical treatment of the material itself, as well as preparation of samples for testing and performing the selected analysis. Chemically grafted polymers were subjected to thermogravimetric analysis to determine their thermal stability. Thermal behavior of materials was studied by differential scanning calorimetry. Also non-isothermal crystallization of samples was observed in order to evaluate the influence of the grafted halogen atom onto the nucleation activity of the polymer. Selected samples were also subjected to dynamic mechanical analysis and tensile test.
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Biocomposite material for 3D print in the field of regenerative medicine
Chaloupková, Kateřina ; Obruča, Stanislav (referee) ; Přikryl, Radek (advisor)
The presented thesis deals with preparation of material for use in regenerative medicine based on poly(3-hydroxybutyrate) and its characterization. In addition to poly (3-hydroxybutyrate), there were used other materials lactic acid (PLA), tricalcium phosphate (TCP) and two types of plasticizers Citroflex®B-6 (CB6) and Syncroflex3114 (S3114). These materials were selected based on their biocompatibility and, in the case of TCP, also bioactivity. TCP allows new bone to grow on the surface of the scaffold. PLA was used to improve the mechanical properties of the material. Both plasticizers have been used to improve the processability of the material. Theoretical part of this work contains a literature review describing basic information about used materials. Aim of the experimental part is to prepare the material, characterization of properties and determination of printability on a 3D printer. The material is examined for thermal properties by thermogravimetric analysis and differential scanning calorimetry. This work also deals with the matter of 3D printing, especially FDM technology. It has been found that materials containing the syncroflex plasticizer are better processed and therefore printed on a 3D printer. The printability tests performed are temperature towers and filling studies. Printed samples were subjected to mechanical tests of tensile and bending tests. Experiments of cytotoxicity and biocompatibility of the material were also performed. Within the work, TCP particles were characterized using a particle size analyzer. The average TCP particle size is 10,76 µm. Using SEM-EDX, the distribution of TCP in sample filaments was subsequently observed, where it was found that by mixing TCP particles with the remaining components of materials, TCP particles agglomerate into formations up to 20 µm in size. Roughness of materials was determined by confocal microscopy. Cytotoxicity was also tested in the extracts of samples on mouse fibroblasts. Cytotoxicity was determined by metabolic activity assay and light microscopy. The metabolic activity test proved the biocompatibility of the observed materials; therefore, it was possible to perform cell proliferation and biocompatibility tests directly on the samples. Assays were performed using human mesenchymal stem cells. DNA quantification was used to determine cell proliferation. Shape of cells was subsequently observed by confocal microscopy. Tests confirmed growth of cells and their appropriate shape. Stem cell differentiation into bone was performed by measuring alkaline phosphatase activity.
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Effect of chemical structure of plasticizer on material properties based on polyhydroxybutyrate
Stehnová, Ivana ; Alexy, Pavol (referee) ; Přikryl, Radek (advisor)
This master’s thesis deals with plasticization of poly(3-hydroxybutyrate), polylactid acid and their blend. It explores effect of chemical structure of plasticizer on mechanical properties of this polymer blend and on its diffusion from the polymer blend. Syntheses of plasticizers based on oligomeric polyadipates, citrates, lactate and esters of 2 ethylhexanoic acid with poly(ethyleneglycol) were carried out. Molecular weight distribution of synthesized plasticizers was determined using gel permeation chromatography. Poly(3-hydroxybutyrate), polylactid acid and their blend were plasticized with synthesized and commercial plasticizers. From commercial, chosed plasticizers were based on citrates and ester of 2-ethylhexanoic acid with poly(ethyleneglycol). Thermal stability of selected commercial plasticizers in polylactid acid was studied using thermogravimetry. Diffusion of plasticizers from poly(3-hydroxybutyrate), polylactid acid and their blend during exposure to 110 °C was also investigated. Mechanical properties of prepared blends were tested by tensile test. Almost all used plasticizers showed positive softening effect in blend. The highest elongation at break was detected for the blend with commercial acetyltributylcitrate, where elongation at break reached 328 % relative to 21 % for neat non-plasticized blend.
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Grafting VTMOS onto PHB
Novotný, Igor ; Petruš, Josef (referee) ; Kučera, František (advisor)
Diploma thesis deals with the grafting of vinyltrimethoxysilane (VTMOS) onto poly(3–hydroxybutyrate)PHB. Subsequent characterization of the amount of grafted VTMOS and changes in the thermal properties associated with the rate of crystallization. The theoretical part deals with mechanism and the influences of grafting. In the experimental part VTMOS was grafted onto PHB without subjecting VTMOS to hydrolysis and subsequent crosslinking. By differential scanning calorimetry (DSC) and Avrami equation, the effect of grafted silane group on pure was studied. The MVR was used to compare the rheological properties of initial PHB, grafted PHB and crosslinked PHB by siloxane linkages.
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Properties of nanocomposite based on PHB and HNT
Stehnová, Ivana ; Pavliňáková, Veronika (referee) ; Přikryl, Radek (advisor)
This bachelor’s thesis deals with nanocomposite containing polyhydroxybutyrate matrix filled with halloysite nanotubes. It summarizes findings about optimization of surface modification of the filler, compatibility between the filler and polymer, distribution of the filler in the composite and effect of the filler surface modification, the composite preparation and the filler content on mechanical properties of the composite. Surface modification of the filler was done using 3-(trimethoxysilyl)propylmethacrylate. Efficiency of the silanization was verified by thermogravimetric analysis and Raman spectroscopy. Concentrates containing the unmodified and the modified nanofiller in poly(vinylacetate) or poly(3-hydroxybutyrate) were prepared. Using these concentrates, composites containing 1 % and 3 % of the filler were prepared. Distribution of the filler in the concentrates and the composites and compatibility between the filler and polymer were observed by scanning electron microscopy. Mechanical properties of the composites were tested by tensile test.
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Isolation of lignin from grape seeds and its application as filler for polyhydroxyalkanoates (PHA)
Vostrejš, Pavel ; Vítová, Eva (referee) ; Kovalčík, Adriána (advisor)
This diploma thesis deals with 1) the preparation of biodegradable polymer films based on polyhydroxyalkanoates (PHA) and 2) their modification by lignin as an active additive. The motivation for this work was to prepare active packaging material for food packaging. Polymer films were prepared by blending of neat crystalline poly(3hydroxybutyrate) (P3HB) and amorphous polyhydroxyalkanoate (PHA). The lignin was isolated from grape seeds derived from grape pomace. The solubility of lignin in chloroform was improved by acetylation. The properties of the isolated lignin were determined by elemental analysis, ash content, and infrared spectroscopy (FTIR). Lignin was used as an active additive for the modification of polymeric films prepared by solution casting of P3HB or P3HB blended with amorphous polyhydroxyalkanoate. The effect of different concentrations of lignin in the range of 1 to 10 % was tested. The lignin type and concentration had a different influence on the final thermal and mechanical behaviour of polymeric films. Lignin increased the values of the Young modulus and tensile strength of the prepared films. Differential scanning calorimetry data confirmed that lignin positively modified crystallization kinetics of P3HB. Thermogravimetry was used to analyse the thermal stability of PHA films. Lignin markedly increased the thermal stability of PHA films. However, acetylated lignin harms the mechanical properties of films. Moreover, this work showed that lignin isolated from grape seeds and added into PHA films proved its high antioxidant capacity. PHA films with lignin displayed much better gas barrier properties compared with PHA films without lignin. The prepared bioactive PHA films fulfil the requirements for sustainable food packaging with high antioxidant capacity and excellent gas barrier properties.
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Optimization of poly(3-hydroxybutyrate) based biocomposite with respect to its printability and mechanical properties
Chaloupková, Kateřina ; Obruča, Stanislav (referee) ; Přikryl, Radek (advisor)
The presented theses deals with preparation and optimalization of biocompatible material based on poly(3-hydroxybutyrate). Other components of prepared samples are polylactid acid, hydroxyapatite and commercially available plasticizer Syncroflex3114. These components were chosen based on their biocompatibility and properties that can be possibly used in tissue engineering. Theoretical part of this theses contains general overview of bone tissue and review of materials used in bone tissue regeneration. Part of this thesis also deals with the problematics of scaffolds. Aim of the experimental part is a planned experiment, which is used to optimize the mixture with respect to printability and mechanical properties. The first step is the preparation of samples based on the proposed conditions and their subsequent processing into a filament with an exact diameter of 1,75 mm for 3D printing using the fused deposition modeling method. From the prepared filaments, test specimens were printed for the following experiments: temperature tower, warping coefficient measurement, bending and pressure test. Data from these experiments were processed using a mathematical model in the form of graphs and equations which show the effect of material components on the measured quantity. It was found that the amount of plasticizer in the sample affects the properties the most. This effect is negative in all cases and worsens the properties of the material. The result of the planned experiment is also a mixture optimized for the best possible printability and mechanical properties (bending modulus 3,3 GPa and pressure modulus 2,3 GPa). With regard to the potential application of the material in bone tissue engineering, the first accelerated biodegradation screening tests were performed for selected samples. The results of accelerated degradation tests are ambiguous and further optimization is needed. Simultaneously with the diploma thesis, biological testing of scaffolds printed on a 3D printer from prepared samples took place. All tested samples were found to be biocompatible.
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Employment of thermophilic bacteria for biodegradation of synthetic and natural polymers
Csölle, Eduard ; Sedlář, Karel (referee) ; Obruča, Stanislav (advisor)
This bachelor’s thesis deals with the employment of thermophilic bacterium Schlegelella thermodepolymerans for biodegradation of selected polymers, namely poly(3-hydroxybutyrate) (PHB), polylactic acid (PLA), and poly(butylene adipate-co-terephthalate) (PBAT). The theoretical part focuses on the properties and origin of these bioplastics, the characteristics of the studied bacteria, and the general course of the biodegradation process. The experimental part discusses the twenty-day cultivation of three tested strains in the presence of the mentioned polymers and the subsequent evaluation of the degradation rate of these materials. The greatest increase in biomass content was observed by spectrophotometry for strain DSM 15344 when cultured on PHB. With blank samples (without polymers), it was shown that for significant growth, the bacteria had to truly utilize the polymers present. Gravimetric analysis of biomass content confirmed that PHB was the most suitable substrate for cultivation. The highest mass losses were recorded for PHB and were around 30 % across all three strains. For strain LMG 21645, the mass has decreased by almost 33 %. The weight losses of PLA and PBAT were considerably lower. Nevertheless, the most significant molecular weight loss was observed by SEC-MALS for PLA, reaching approximately 80 % for strain DSM 15264. SEM analysis of the polymer surface confirmed that the biodegradation of PHB occurs by enzymatic surface erosion. In contrast, the PLA and PBAT samples did not show any signs of biodegradation.
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Study of the release of active substances from PHA-based particles
Čech, Jan ; Mikulíková, Renata (referee) ; Kovalčík, Adriána (advisor)
This bachelor thesis deals with the study of the release kinetics of caffeic acid and acetylsalicylic acid from polylactic acid, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and poly(3-hydroxybutyrate)-based microparticles. In the theoretical part, the mechanical and thermal properties of polyhydroxyalkanoates, their biological synthesis by microorganisms, their industrial extraction from biomass and applications are described. Furthermore, the properties of PHA microparticles, their use as carriers, the most common microparticle preparations and the release method of the loaded drug are described. In the experimental part, PLA, P(3HB) and P(3HB-co-4HB) based microparticles prepared by the solvent evaporation emulsion method were characterized by dynamic light scattering. Subsequently, caffeic acid or acetylsalicylic acid was incorporated into these microparticles, and the release kinetics of the active ingredient was observed spectrophotometrically for one week. Once measurement of the releasing kinetics ended, microparticles were again measured by DLS and compared with the characterized microparticles before releasing kinetics. Finally, the encapsulation efficiency and microparticle recovery were calculated.
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Preparation of methacrylated hydroxybutyrates monomers and polymers
Liška, Marek ; Mgr. Petra Zbořilová, Ph.D (referee) ; Figalla, Silvestr (advisor)
The aim of this work is the study, design, and preparation of methacrylated derivatives of poly(3-hydroxybutyrate) and the subsequent preparation of polymers from the prepared precursors. A total of six compounds were prepared. The prepared compounds include methyl-3-hydroxybutyrate and ethyl-3-hydroxybutyrate prepared by alcoholytic depolymerization with monofunctional alcohol and their methacrylated derivatives. The preparation of ethylene glycol terminated oligomer of 3-hydroxybutyrate prepared via depolymerization using ethylene glycol in two ways is also an essential part of the work. The first way involves depolymerization using conventional heating and the second one explores the preparation of a series of oligomers with different molecular weights using microwave heating. Methacrylated derivatives of the prepared oligomers were also prepared. The prepared compounds and their actual preparation are characterized using multiple analytical methods including VPO, NMR, GPC, FT-IR, LC-MS, and DSC. A series of polymers were obtained from the prepared compounds by radical polymerization using purple light (with wavelength 405 nm) as the energy source. The prepared polymer networks were characterized by DSC and their tensile strengths were tested.
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