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Vliv strukturních a procesních parametrů na vlastnosti polymerních nanokompozitů
Zárybnická, Klára ; Žídek, Jan (oponent) ; Jančář, Josef (vedoucí práce)
Cílem této práce je studium strukturních a procesních parametrů, které řídí disperzi nanočástic v roztocích polymerů, aby bylo možno připravovat na míru polymerní nanokompozity s požadovaným prostorovým uspořádáním nanočástic. V práci se řeší především vliv různých komponent jako jsou polymerní matrice, nanočástice a rozpouštědla, ve kterých dochází k mísení matrice a nanočástic. Použité komponenty mají vliv na výsledný disperzní stav částic a tím jsou ovlivněny i vlastnosti zkoumaných materiálů jako je například teplota skelného přechodu, tuhost materiálu a reologické vlastnosti.
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Biomimetické polymer/grafenové vrstevnaté nanokompozity
Dostalík, Petr ; Ondreáš, František (oponent) ; Zbončák, Marek (vedoucí práce)
Tato bakalářská práce se zaobírá přípravou biomimetických polymer/grafenových vrstevnatých nanokompozitů. Za účelem přípravy nanokompozitů bylo nejdříve potřebné připravit vhodný grafénový materiál. Pro jeho přípravu byla zvolena Tour-Marcanova metoda, u které byl zkoumán vliv doby oxidace na strukturu výsledného grafen/grafit oxidu. Z výsledků strukturních analýz bylo vyhodnoceno, že po 4 hod. oxidace došlo k interkalaci struktury grafitu, vzniku kyslíkových skupiny (zejména epoxidových skupin) a zvětšení mezi-rovinné vzdálenosti za vzniku grafit oxidu (GO). Prodloužení oxidačního času nevedlo k zásadním změnám ve struktuře připraveného GO. Nanokompozity byly připraveny metodou spočívající v odpaření rozpouštědla. Jako matrice byl použit polární polymer – polyvinylalkohol (PVAl) za předpokladu silných interakcí mezí GO a PVAl. Za účelem podpoření interkalace GO byl v procesu přípravy nanokompozitů použit ultrazvukový dispergátor, jehož vliv se projevil nárůstem mezi-rovinné vzdálenosti GO v nanokompozitech. Bylo pozorováno, že mezi-rovinné vzdálenosti GO i krystalů PVAl jsou ovlivněny koncentrací jednotlivých složek v nanokompozitech, což nasvědčuje možné modifikaci krystalické struktury PVAl. Strukturní analýzou bylo zjištěno, že vrstvy GO byly v kompozitu úspěšně orientovány v jednom směru.
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Thermomechanical response of polymer nanocomposites with preparation protocol controlled nanoparticle dispersion
Ondreáš, František ; Chodák,, Ivan (oponent) ; Matějka,, Libor (oponent) ; Jančář, Josef (vedoucí práce)
This thesis is focused on a fundamental investigation of nanoparticle self-assembly in polymer liquids and on properties of the prepared polymer nanocomposites with controlled nanoparticle dispersion. Despite recent progress in understanding polymer nanocomposites, there are still unfilled gaps in the fundamental knowledge of relaxation phenomena and mechanical properties of various nanostructures that would provide key information for designing hierarchical or multidomain nanocomposites processable by additive manufacturing technologies. The emphasis was put on the investigation of the preparation protocol influence on the final dispersion state, preparation of various nanostructures – individually dispersed NPs, chain bound clusters, and contact aggregates at a constant composition, and determination of their relaxation and mechanical properties. Moreover, nanoparticles were utilized as “probes” in polymer matrix that affect the segmental ordering and the relaxation dynamics of polymer chains. This approach can help to derive the relationship between the nano scale segmental dynamics and macro scale mechanical properties of polymer glasses. It is a challenging fundamental scientific problem with an extreme technological importance. Non-grafted ceramic nanoparticles and polymer glasses were used to avoid the focus to deflect from the study of the nanoparticle–polymer interaction influence towards the influence of the graft–polymer interaction or the altered crystalline structure. A thorough investigation was performed for the PMMA/SiO2 model system and subsequently broadened to systems with different matrices (PC and PS) and nanoparticles (ZnO2 and Fe2O3) in order to generalize the obtained results. Nanostructure, volume fraction, and composition dependences of relaxation – glass transition temperature, reptation time, plateau modulus, number of entanglements, and mechanical properties – yield stress, yield drop, elastic modulus, strain hardening modulus, and creep response were determined. Achieved results were interpreted by means of the recent models. The determined relaxational and mechanical properties were connected to provide information about the molecular processes responsible for the mechanical response of the polymer nanocomposites.
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Preparation and characterization of self assembled polymer nanocomposites
Lepcio, Petr ; Žídek, Jan (oponent) ; Jančář, Josef (vedoucí práce)
Polymer nanocomposites based on polyhedral oligomeric silsesquioxanes (POSS) are promising field which could potentially utilize self-assembly approach in designing new materials. In this thesis, a preparation protocol of octaphenyl-POSS/PS, octamethyl-POSS/PMMA and octamethyl-POSS/PS systems was described and thermomechanic properties in solid state and rheological properties in solution were investigated. The obtained results are discussed with focus on nanoparticles dispersion state theories.
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Cellular polymer nanocomposites
Zárybnická, Klára ; Crosby, Alfred (oponent) ; Lehocký,, Marián (oponent) ; Jančář, Josef (vedoucí práce)
This dissertation thesis deals with the preparation and characterization of polymer nanocomposite foams with a focus on means to control their structure at multiple length scales and application in 3D printing in their fabrication. The aim of this work is to investigate polymer nanocomposite with hierarchical structure – from the nano-, through the micro to macro scale. The structural properties of polymer nanocomposites prepared from glassy polymers by the solvent-casting method were investigated in the first part of the work. It has been shown that the difference in the solubility parameters of the polymer and the solvent plays a crucial role. This finding has been verified for systems containing various nanoparticles, polymers, and solvents. With the knowledge of the general principles controlling the structure of nanocomposites, impact polystyrene filled with nanosilica was investigated in greater detail. These nanocomposites were used for the preparation of nanocomposite foams. The porous structure was achieved using a thermal chemical blowing agent azodicarbonamide. The filaments were extruded and the material was processed by 3D printing into the required shapes and foamed. The result was a hierarchical system with the organization of the structure from nano (organization of nanoparticles), through micro (two-component polymer blend structure and foam structure) to macro scale (foam structure and 3D printed design). The effect of nanoparticles on the structure and the thermal and mechanical properties of polymeric foams were observed. The nanoparticles operate as a nucleating agent in the formation of the foam. Pores are easily formed on their surface so that with the content of nanoparticles in the system smaller pores have been formed, which helped to make the foam fine and homogeneous. The presence of nanoparticles changed the surface energy of the blowing agent grains, thanks to which it decomposed at lower temperatures and foaming was even faster. At the same time, nanoparticles have the potential to reinforce foam walls and thus improve mechanical properties. 3D printing is a popular and widespread technique, due to its simplicity it is in many laboratories and test institutions, therefore the demand for filaments with special properties is growing. The material developed in this dissertation is essentially a finished and characterized product that could contribute to the satisfaction of this claim.
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Magnetically assembled nanoparticle structures and their effect on mechanical response of polymer nanocomposites
Zbončák, Marek ; Khúnová,, Viera (oponent) ; Crosby, Alfred (oponent) ; Jančář, Josef (vedoucí práce)
Magnetically directed self-assembly in polymer nanocomposites is studied in this dissertation thesis. Structuring of the polymer nanocomposites by application of relatively weak external magnetic fields (B=0-50 mT) has been proven to be convenient method for the control of their nano- and microstructure. The effect of the field strength, particle loading, viscosity and assembling time on the resulted structure was studied in different systems such as photopolymer, polyurethane or colloidally dispersed magnetic nanoparticles in acetone with a small amount of dissolved polymer. Self-assembled structures – without application of the external magnetic field exhibit a multi-step aggregation into nanoparticle assemblies with a complex shape. By the calculation of interaction energies between the nanoparticles, magnetic interactions were attributed to be mainly responsible for the aggregation in self-assembled systems. With an increasing magnetic field, magnetic nanoparticles are rapidly arranged into high aspect ratio one-dimensional particle chains with a homogenous orientation in the bulk polymer matrix. After prolonged assembling time, the structures gradually grow from small submicro structures to large microscopic superstructures. This method exhibits large potential to be used for controlled creation of wide variety of structures in polymer nanocomposites suitable for technological applications and/or for fundamental studies. Magnetically structured polymer nanocomposites show significant directional anisotropy of composite’s stiffness at the temperatures above glass transition of the system while there is no effect on the mechanical response in glassy state. Longitudinally oriented structures exhibit much stronger effect on the composite’s stiffness. Reinforcing effectivity exhibits temperature dependent course with a maximum obtained approximately 60 °C above glass transition. The structure of magnetically assembled polymer nanocomposites was described by multi-level hierarchic model of material. Micromechanics was used to address the orientation dependent reinforcement and temperature dependent stiffness of the hybrid nanoparticle-polymer structures. Load carrying capability, deformation and non-zero stiffness of the hybrid structures were attributed to be responsible for the reinforcement of the polymer nanocomposites. The presence of polymer bridges between nanoparticles transmitting the stress through the magnetic structures is proposed to be essential for the mechanical properties of polymer nanocomposites and for stiffness of the hybrid structures.
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Cellular polymer nanocomposites
Zárybnická, Klára ; Crosby, Alfred (oponent) ; Lehocký,, Marián (oponent) ; Jančář, Josef (vedoucí práce)
This dissertation thesis deals with the preparation and characterization of polymer nanocomposite foams with a focus on means to control their structure at multiple length scales and application in 3D printing in their fabrication. The aim of this work is to investigate polymer nanocomposite with hierarchical structure – from the nano-, through the micro to macro scale. The structural properties of polymer nanocomposites prepared from glassy polymers by the solvent-casting method were investigated in the first part of the work. It has been shown that the difference in the solubility parameters of the polymer and the solvent plays a crucial role. This finding has been verified for systems containing various nanoparticles, polymers, and solvents. With the knowledge of the general principles controlling the structure of nanocomposites, impact polystyrene filled with nanosilica was investigated in greater detail. These nanocomposites were used for the preparation of nanocomposite foams. The porous structure was achieved using a thermal chemical blowing agent azodicarbonamide. The filaments were extruded and the material was processed by 3D printing into the required shapes and foamed. The result was a hierarchical system with the organization of the structure from nano (organization of nanoparticles), through micro (two-component polymer blend structure and foam structure) to macro scale (foam structure and 3D printed design). The effect of nanoparticles on the structure and the thermal and mechanical properties of polymeric foams were observed. The nanoparticles operate as a nucleating agent in the formation of the foam. Pores are easily formed on their surface so that with the content of nanoparticles in the system smaller pores have been formed, which helped to make the foam fine and homogeneous. The presence of nanoparticles changed the surface energy of the blowing agent grains, thanks to which it decomposed at lower temperatures and foaming was even faster. At the same time, nanoparticles have the potential to reinforce foam walls and thus improve mechanical properties. 3D printing is a popular and widespread technique, due to its simplicity it is in many laboratories and test institutions, therefore the demand for filaments with special properties is growing. The material developed in this dissertation is essentially a finished and characterized product that could contribute to the satisfaction of this claim.
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Biomimetické polymer/grafenové vrstevnaté nanokompozity
Dostalík, Petr ; Ondreáš, František (oponent) ; Zbončák, Marek (vedoucí práce)
Tato bakalářská práce se zaobírá přípravou biomimetických polymer/grafenových vrstevnatých nanokompozitů. Za účelem přípravy nanokompozitů bylo nejdříve potřebné připravit vhodný grafénový materiál. Pro jeho přípravu byla zvolena Tour-Marcanova metoda, u které byl zkoumán vliv doby oxidace na strukturu výsledného grafen/grafit oxidu. Z výsledků strukturních analýz bylo vyhodnoceno, že po 4 hod. oxidace došlo k interkalaci struktury grafitu, vzniku kyslíkových skupiny (zejména epoxidových skupin) a zvětšení mezi-rovinné vzdálenosti za vzniku grafit oxidu (GO). Prodloužení oxidačního času nevedlo k zásadním změnám ve struktuře připraveného GO. Nanokompozity byly připraveny metodou spočívající v odpaření rozpouštědla. Jako matrice byl použit polární polymer – polyvinylalkohol (PVAl) za předpokladu silných interakcí mezí GO a PVAl. Za účelem podpoření interkalace GO byl v procesu přípravy nanokompozitů použit ultrazvukový dispergátor, jehož vliv se projevil nárůstem mezi-rovinné vzdálenosti GO v nanokompozitech. Bylo pozorováno, že mezi-rovinné vzdálenosti GO i krystalů PVAl jsou ovlivněny koncentrací jednotlivých složek v nanokompozitech, což nasvědčuje možné modifikaci krystalické struktury PVAl. Strukturní analýzou bylo zjištěno, že vrstvy GO byly v kompozitu úspěšně orientovány v jednom směru.
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Thermomechanical response of polymer nanocomposites with preparation protocol controlled nanoparticle dispersion
Ondreáš, František ; Chodák,, Ivan (oponent) ; Matějka,, Libor (oponent) ; Jančář, Josef (vedoucí práce)
This thesis is focused on a fundamental investigation of nanoparticle self-assembly in polymer liquids and on properties of the prepared polymer nanocomposites with controlled nanoparticle dispersion. Despite recent progress in understanding polymer nanocomposites, there are still unfilled gaps in the fundamental knowledge of relaxation phenomena and mechanical properties of various nanostructures that would provide key information for designing hierarchical or multidomain nanocomposites processable by additive manufacturing technologies. The emphasis was put on the investigation of the preparation protocol influence on the final dispersion state, preparation of various nanostructures – individually dispersed NPs, chain bound clusters, and contact aggregates at a constant composition, and determination of their relaxation and mechanical properties. Moreover, nanoparticles were utilized as “probes” in polymer matrix that affect the segmental ordering and the relaxation dynamics of polymer chains. This approach can help to derive the relationship between the nano scale segmental dynamics and macro scale mechanical properties of polymer glasses. It is a challenging fundamental scientific problem with an extreme technological importance. Non-grafted ceramic nanoparticles and polymer glasses were used to avoid the focus to deflect from the study of the nanoparticle–polymer interaction influence towards the influence of the graft–polymer interaction or the altered crystalline structure. A thorough investigation was performed for the PMMA/SiO2 model system and subsequently broadened to systems with different matrices (PC and PS) and nanoparticles (ZnO2 and Fe2O3) in order to generalize the obtained results. Nanostructure, volume fraction, and composition dependences of relaxation – glass transition temperature, reptation time, plateau modulus, number of entanglements, and mechanical properties – yield stress, yield drop, elastic modulus, strain hardening modulus, and creep response were determined. Achieved results were interpreted by means of the recent models. The determined relaxational and mechanical properties were connected to provide information about the molecular processes responsible for the mechanical response of the polymer nanocomposites.
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Magnetically assembled nanoparticle structures and their effect on mechanical response of polymer nanocomposites
Zbončák, Marek ; Khúnová,, Viera (oponent) ; Crosby, Alfred (oponent) ; Jančář, Josef (vedoucí práce)
Magnetically directed self-assembly in polymer nanocomposites is studied in this dissertation thesis. Structuring of the polymer nanocomposites by application of relatively weak external magnetic fields (B=0-50 mT) has been proven to be convenient method for the control of their nano- and microstructure. The effect of the field strength, particle loading, viscosity and assembling time on the resulted structure was studied in different systems such as photopolymer, polyurethane or colloidally dispersed magnetic nanoparticles in acetone with a small amount of dissolved polymer. Self-assembled structures – without application of the external magnetic field exhibit a multi-step aggregation into nanoparticle assemblies with a complex shape. By the calculation of interaction energies between the nanoparticles, magnetic interactions were attributed to be mainly responsible for the aggregation in self-assembled systems. With an increasing magnetic field, magnetic nanoparticles are rapidly arranged into high aspect ratio one-dimensional particle chains with a homogenous orientation in the bulk polymer matrix. After prolonged assembling time, the structures gradually grow from small submicro structures to large microscopic superstructures. This method exhibits large potential to be used for controlled creation of wide variety of structures in polymer nanocomposites suitable for technological applications and/or for fundamental studies. Magnetically structured polymer nanocomposites show significant directional anisotropy of composite’s stiffness at the temperatures above glass transition of the system while there is no effect on the mechanical response in glassy state. Longitudinally oriented structures exhibit much stronger effect on the composite’s stiffness. Reinforcing effectivity exhibits temperature dependent course with a maximum obtained approximately 60 °C above glass transition. The structure of magnetically assembled polymer nanocomposites was described by multi-level hierarchic model of material. Micromechanics was used to address the orientation dependent reinforcement and temperature dependent stiffness of the hybrid nanoparticle-polymer structures. Load carrying capability, deformation and non-zero stiffness of the hybrid structures were attributed to be responsible for the reinforcement of the polymer nanocomposites. The presence of polymer bridges between nanoparticles transmitting the stress through the magnetic structures is proposed to be essential for the mechanical properties of polymer nanocomposites and for stiffness of the hybrid structures.
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