The presented dissertation thesis deals with the polymer polyhydroxybutyrate and other biopolymers as a basic building block for the construction of micro- and nanoscopic structures and materials used in food and cosmetics. In the theoretical part, current literary review is prepared to introduce the basics of this application field. The practical part of the work is composed of three blocks developed during the doctoral study. In the first and most important part are summarized comments to the academic and patent outputs, where among the academic ones it is possible to find two peer-reviewed articles dealing with the electrostatic and wet spinning of PHB and properties of prepared materials. The patent outputs consist of several accepted and applied projects, which summarize results on both PHB spinning methods, but also on general approaches enabling the processing of PHB into forms enabling many applications in food and cosmetics. Second part was focused on the patented composition of the UV protection cream based on the prepared nanoscopic and micro- morphologies of PHB. The third block summarizes results focused predominantly on the electrostatic spinning of PHB and other biopolymers. Finally, a short chapter containing a brief description of projects that were in a way related to the dissertation topic, but rather practical development work in Central Tanzania and West Africa, which draw on knowledge and contacts gained during studies at FCH BUT Brno.

Boli pripravené kryty rán na bázi prírodných látok polyvinyl alcohol/ hyaluronan/ strieborné nanočastice (PVA/ HA/ Ag-NPs). Hyaluronan bol použitý ako redukčné a stabilizačné činidlo pre syntézu nanočastíc striebra. Pri príprave Ag-NPs boli testované viaceré parametre ako koncentrácia dusičnanu strieborného ako zdroja Ag-NPs (0,01; 0,1;0,5;1 M), koncentrácia kyseliny hyalurónovej (1,2 %) a jej rozdielna molekulová hmotnosť. Kryty rán z nanovlákien boli pripravené pomocou techniky electro-spinning z roztokov líšiacich sa pomerom PVA a HA/Ag-NPs (100; 90/10; 80/20; 60/40; 50/50). Vlastnosti nanokompozitu HA/Ag-NPs boli hodnotené pomocou TEM, reológie, DLS, XRD, UV/Vis spektroskopie a kryty rán boli charakterizované pomocou SEM, TGA, FTIR a ťahovej skúšky.

Tato práce se zabývá charakterizací nanovláken na bázi polyvinylidenfluoridu. Zaměření práce je na piezoelektrické vlastnosti vlákna, které jsou studovány metodou piezoelektrické silové mikroskopie. Takto byly měřeny dva typy odlišných vzorků, které se lišily v parametrech výroby. Odlišnosti vláken v jejich fázovém složení byly také zkoumány za využití Ramanovy spektroskopie a infračervené spektroskopie s Fourierovou transformací. Chemická analýza povrchu a jeho stavu proběhla pomocí rentgenové fotoelektronové spektroskopie. Různé uspořádání nanovláken spolu s jejich průřezem bylo pozorováno rastrovacím elektronovým mikroskopem za využití fokusovaného iontového svazku. Rovněž byla zkoumána smáčivost a kontaktní úhel povrchu vzorků s demineralizovanou vodou. Bylo zjištěno, že vyšší rychlost otáček válce během procesu elektrostatického zvlákňování má velmi významný vliv na jejich uspořádání a tím i na parametry ovlivňující tvorbu piezoelektrického jevu a dalších materiálových vlastností.

The thesis deals with the principal heating design of the electrospinning electrode. These electrodes are fed with high voltage (tens of kV), which is an essential part of the device for the nanofibres production. This thesis presents the research of possible solutions of the heating and also it analyzes some principles of the nanofibre production. Furthermore, the work presents electrical schematics and PCB of the heating module. The aim of this work is to propose such a solution of heating that makes spinning from melt realizable in the device for 4SPIN ® nanofibres production.

The electrospinning process of polymer solutions is affected by many different parameters that can be divided into solution parameters, process parameters, and ambient parameters. This study is focused on characteristics of a polymer and its solution, which are ranging into the solution parameters. The aim of this study is to compare poly(ethylene oxide) characteristics in the relation to electrospinning of hyaluronic acid, to find the difference between them using available analytic, thermic and spectral methods, and to define the influence of properties on polymeric solutions behavior during electrospinning. It was find that poly(ethylene oxides) obtained from two different sources behave differently in an electrostatic field, although their molar mass is declared as the same. It was also confirmed that the electrospinning process of polymeric solutions is affected mainly by their viscosity and conductivity. This two properties are determined especially by the molar mass of polymer and also by the content of impurities or content of some another polymer during electrospinning of mixed solution.

Electrospinning has been the focus of countless studies for the past decades for applications, including but not limited to, filtration, tissue engineering, and catalysis. Electrospinning is a one-step process for producing nano- and/or micro-fibrous materials with diameters ranging typically from 50 to 5000 nm. The simulation algorithm presented here is based on a novel mass-spring-damper (MSD) approach devised to incorporate the mechanical properties of the fibers in predicting the formation and morphology of the electrospun fibers as they travel from the needle toward the collector, and as they deposit on the substrate. This work is the first to develop a physics-based (in contrast to the previously-developed geometry-based) computational model to generate 3-D virtual geometries that realistically resemble the microstructure of an electrospun fibrous material with embedded particles, and to report on the filtration performance of the resulting composite media. In addition, this work presents a detailed analysis on the effects of electrospinning conditions on the microstructural properties (i.e. fiber diameter, thickness, and porosity) of polystyrene and polycaprolactone fibrous materials. For instance, it was observed that porosity of a PS electrospun material increases with increasing the needle-to-collector distance, or reducing the concentration of PS solution. The computational tool developed in this work allows one to study the effects of electrospinning parameters such as voltage, needle-to-collector distance (NCD), or polymer concentration, on thickness and porosity of the resulting fibrous materials. Using our MSD formulations, a new approach is also developed to model formation and growth of dust-cakes comprised of non-overlapping non-spherical particles, for the first time. This new simulation approach can be used to study the morphology of a dust-cake and how it impacts, for instance, the filtration efficiency of a dust-loaded filter, among many other applications.

Philosophiae Doctor - PhD / The application of porous materials into industrial hydrogen (H2) storage systems is based on their use in combination with high-pressure cylinders. The processing of metal-organic frameworks (MOF) powders into shaped forms is therefore imperative in order to counteract the adverse effects of poor packing of powders in cylinders. The fabrication of shaped MOFs has, however, been shown to be accompanied by compromised properties such as surface areas, gravimetric and volumetric H2 capacities, and also the working/deliverable H2 capacities in comparison to MOF powders.

Electrospinning is a useful technique that can generate micro- and nano-meter sized fibers from polymer materials. Modification of the electrospinning parameters and apparatus can generate nanofibers for use in diverse applications ranging from tissue engineering to nanocomposite fabrication; however, electrospun fibers are typically collected in a random orientation and over large areas limiting their applications.  Here we present several methods to control the deposition of electrospun nanofibers, such as the use of a single auxiliary electrode ring and a negatively charged collector substrate to control the deposition area and the construction of a parallel electrode collector known as the triple electrode setup to control the uniaxial alignment of nanofibers. The numerous constructed setups were advanced by the use of electric field computations to assess the distribution of the electric field and its effect on the deposition behavior and morphology of the electrospun nanofibers. The electrostatic force imposed by the auxiliary electrodes provides converged electric fields that direct the nanofibers to their desired deposition targets. Here it is shown that the use of the auxiliary electrode ring dramatically decreased the deposition area of nanofibers, the negatively charged substrate yielded more uniform nanofibers and the triple electrode setup is a viable method to achieve uniaxially aligned nanofiber mats.    The electrospinning of copolymers appears as an attractive option for enhancing the overall properties of nanofibers as it offers possibility of an intrinsic control of the polymeric material itself. The poly(methyl methacrylate)-graft-poly(dimethylsiloxane) graft copolymer  (PMMA-g-PDMS) is considered to be an organic-inorganic hybrid material with much potential in its use in nanocomposites, and in this work has been successfully synthesized and electrospun via the various constructed electrospinning setups.   In the final elements of this work, the triple electrode setup is used in combination with a dynamic rotating collector to yield a novel collector and has been successfully used to produce PMMA-g-PDMS nanofiber sheets that were further incorporated in a PDMS matrix to yield nanocomposite sheets. A variant of the triple electrode setup with partially insulated electrodes is devised in combination with a methodology to remove the nanofibers from the collector. The nanofibers once removed and dried were incorporated in a PDMS matrix to yield nanocomposites. The preferential dissolution of the fibers from the matrix rendered the fibers to templates and a final porous material with uniaxial nanochannels could be obtained.   This work is believed to be able to lead to a better understanding of the mechanisms of nanofiber deposition and alignment, and should be of help to the design of more practical collecting structures, hence promoting the applications of the electrospinning technique.

Indiana University-Purdue University Indianapolis (IUPUI) / This study represents a cost-effective method to advance the physical and mechanical properties of carbon fiber-reinforced polymer (CFRP) prepreg composite materials, where electrospun multiwalled carbon nanotubes (CNTs)/epoxy nanofibers fabricated and deposited in between the layers of traditional CFRP prepreg composite. CNT-aligned epoxy nanofibers were uniformly formed by an optimized electrospinning method. Electrospinning is considered one of the most flexible, low-cost, and globally recognized methods for generating continuous filaments from submicron to tens of nanometer diameter. Nanofilaments were incorporated precisely on the layers of prepreg to accomplish increased adhesion and interfacial bonding, leading to increased strength and enhancements in more mechanical properties. As a result, the modulus of the epoxy and CNT/epoxy nanofibers were revealed to be 3.24 GPa and 4.84 GPa, leading to 49% enhancement. Furthermore, interlaminar shear strength (ILSS) and fatigue performance at high-stress regimes improved by 29% and 27%, respectively. Barely visible impact damage (BVID) energy improved considerably by up to 45%. The thermal and electrical conductivities were also increased considerably because of the highly conductive CNT networks present in between the CFRP layers. The newly introduced approach was able to deposit high content uniform CNTs at the ply interface of prepregs to enhance the CFRP properties, that has not been achieved in the past because of the randomly oriented high viscosity CNTs in epoxy resins.

This study represents a cost-effective method to advance the physical and mechanical properties of carbon fiber-reinforced polymer (CFRP) prepreg composite materials, where electrospun multiwalled carbon nanotubes (CNTs)/epoxy nanofibers fabricated and deposited in between the layers of traditional CFRP prepreg composite. CNT-aligned epoxy nanofibers were uniformly formed by an optimized electrospinning method. Electrospinning is considered one of the most flexible, low-cost, and globally recognized methods for generating continuous filaments from submicron to tens of nanometer diameter. Nanofilaments were incorporated precisely on the layers of prepreg to accomplish increased adhesion and interfacial bonding, leading to increased strength and enhancements in more mechanical properties. As a result, the modulus of the epoxy and CNT/epoxy nanofibers were revealed to be 3.24 GPa and 4.84 GPa, leading to 49% enhancement. Furthermore, interlaminar shear strength (ILSS) and fatigue performance at high-stress regimes improved by 29% and 27%, respectively. Barely visible impact damage (BVID) energy improved considerably by up to 45%. The thermal and electrical conductivities were also increased considerably because of the highly conductive CNT networks present in between the CFRP layers. The newly introduced approach was able to deposit high content uniform CNTs at the ply interface of prepregs to enhance the CFRP properties, that has not been achieved in the past because of the randomly oriented high viscosity CNTs in epoxy resins.