Iskanje po katalogu digitalne knjižnice

Ključne besede: polyacetylenes, emulsion-templating, π-conjugated networks, macroporous polymers, heterogeneous photocatalysis
Objavljeno v DKUM: 29.08.2024; Ogledov: 71; Prenosov: 2
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Ključne besede: RAFT polymerisation, polyHIPEs, hypercrosslinking, porous polymers, porosity
Objavljeno v DKUM: 10.05.2024; Ogledov: 148; Prenosov: 13
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Opis: Highly porous metal oxide−polymer nanocomposites are attracting considerable interest due to their unique structural and functional features. A porous polymer matrix brings properties such as high porosity and permeability, while the metal oxide phase adds functionality. For the metal oxide phase to perform its function, it must be fully accessible, and this is possible only at the pore surface, but functioning surfaces require controlled engineering, which remains a challenge. Here, highly porous nanocomposite beads based on thin metal oxide nanocoatings and polymerized high internal phase emulsions (polyHIPEs) are demonstrated. By leveraging the unique properties of polyHIPEs, i.e., a three-dimensional (3D) interconnected network of macropores, and high-precision of the atomic-layer-deposition technique (ALD), we were able to homogeneously coat the entire surface of the pores in polyHIPE beads with TiO$_2$-, ZnO-, and Al$_2$O$_3$-based nanocoatings. Parameters such as nanocoating thickness, growth per cycle (GPC), and metal oxide (MO) composition were systematically controlled by varying the number of deposition cycles and dosing time under specific process conditions. The combination of polyHIPE structure and ALD technique proved advantageous, as MO-nanocoatings with thicknesses between 11 ± 3 and 40 ± 9 nm for TiO$_2$ or 31 ± 6 and 74 ± 28 nm for ZnO and Al$_2$O$_3$, respectively, were successfully fabricated. It has been shown that the number of ALD cycles affects both the thickness and crystallinity of the MO nanocoatings. Finally, the potential of ALD-derived TiO$_2$-polyHIPE beads in photocatalytic oxidation of an aqueous bisphenol A (BPA) solution was demonstrated. The beads exhibited about five times higher activity than nanocomposite beads prepared by the conventional (Pickering) method. Such ALD-derived polyHIPE nanocomposites could find wide application in nanotechnology, sensor development, or catalysis.
Ključne besede: nanovlakna, aerosoli, filtracija, emulsion-templating, macroporous polymers, atomic-layer-deposition
Objavljeno v DKUM: 15.04.2024; Ogledov: 239; Prenosov: 13
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Opis: The development of n-type organic semiconductors has evolved significantly slower in comparison to that of p-type organic semiconductors mainly due to the lack of electron-deficient building blocks with stability and processability. However, to realize a variety of organic optoelectronic devices, high-performance n-type polymer semiconductors are essential. Herein, conjugated microporous polymers (CMPs) comprising isoindigo acceptor units linked to benzene or pyrene donor units (BI and PI) showing n-type semiconducting behavior are reported. In addition, considering the challenges of deposition of a continuous and homogeneous thin film of CMPs for accurate Hall measurements, a plasma-assisted fabrication technique is developed to yield uniform thin films. The fully conjugated 2D networks in PI- and BI-CMP films display high electron mobility of 6.6 and 3.5 cm2 V−1 s−1, respectively. The higher carrier concentration in PI results in high conductivity (5.3 mS cm−1). Both experimental and computational studies are adequately combined to investigate structure–property relations for this intriguing class of materials in the context of organic electronics.
Ključne besede: conjugated microporous polymers, isoindigo, semiconductors, conductivity, electron mobility
Objavljeno v DKUM: 03.04.2024; Ogledov: 213; Prenosov: 12
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Opis: PolyHIPEs are highly porous polymers with an interconnecting porous structure. They have found usage in the removal of pollutants, water clean-up, oil spill removal, catalysis, controlled release of active compounds, wound dressing and tissue engineering. The wide applicability of polyHIPEs is possible through their inherent porosity and chemical diversity. The aim of this dissertation was to increase the chemical diversity of polyHIPEs, develop an efficient method for the synthesis of polyHIPE beads and to use natural resources for the synthesis of polyHIPEs, subsequently, paving the pathway to more sustainable synthetic procedures. PolyHIPEs tend to have poor mechanical properties, therefore, it was crucial to investigate the influence of the internal phase volume, initation type (photo vs thermal) and monomer functionality on the mechanical and morphological properties of thiol-ene polyHIPEs. The results show that the main factors influencing the morphological and mechanical properties are the monomer structure and the internal phase volume. Besides the inherent porosity and chemical versatility typical of polyHIPEs, they can also be produced in various shapes, e.g., monoliths, membranes and beads. Therefore, the dissertation also focuses on the synthesis of polyHIPE beads. The polyHIPE beads were produced through the usage of water-in-oil-in-water (W/O/W) multiple emulsions. To enable the synthesise of open porous polyHIPE beads, thiol-ene polymerisation was combined with photopolymerisation to guarantee a rapid polymerisation prior the break-down of the multiple emulsion. Consequently, it was possible to synthesise polyHIPE beads. The first study showed that by altering the thiol to acrylate ratio in favour of the acrylate the degradation rate of the synthesised polyHIPE beads gets reduced. Additionally, it was demonstrated that the beads can be readily functionalised with allyl amine and used for the adsorption of methylene blue (12.0 mg/g in 24 hours). The next study combined polyHIPE beads with magnetic nanoparticles (MNPs) to produce magnetic polyHIPE beads which were used for the removal of Pb2+. To produce the magnetic polyHIPE beads, magnetic nanoparticles (MNPs) were added to the organic phase. The MNPs get incorporated into the polymer-network after the polymerisation, therefore, forming magnetic polyHIPE beads. The MNPs were shown to influence the morphology and the size of the beads. Additionally, the polyHIPE beads were shown to remove up to 97.0 % of Pb2+ after 24 hours from a 2.9 mg/L solution of Pb2+. In the last study related to the synthesis of polyHIPE beads, functional polyHIPE beads were produced and then functionalised to enable the binding of the enzyme invertase. These beads were then utilised for the hydrolysis of sucrose. The conversion of sucrose to glucose and fructose was 100% after 60 minutes for the polyHIPE beads, while the conversion for non-porous beads was only 6.5%. The last part of the thesis focused on more sustainable/natural approaches to polyHIPE synthesis. The first study utilised limonene as a replacement to conventional solvents (e.g., cyclohexane) in the production of O/W HIPEs and the polymerisation thereof into polyHIPEs. It was shown that limonene can be used as an efficient replacement in the production of polyHIPEs. The next study used natural resources (terpenoids) which were modified to contain polymerisable units, which were used for the synthesis of terpenoid-based polyHIPEs. The synthesised monomers were then crosslinked with 5 and 10 mol. % TMPTA to form polyHIPEs, consequently producing porous polymers. The last study in this thesis used the terpenes limonene, carvone and myrcene to produce bio-based polyHIPEs by utilising multifunctional acrylates (PETA and TMPTA) as the comonomers. This study demonstrates that it is possible to prepare polyHIPEs from commercially available terpenes, therefore, moving the field of polyHIPEs into a more sustainable direction.
Ključne besede: HIPE, PolyHIPE, Multiple Emulsions, Functional polyHIPEs, Natural Polymers, Terpenes
Objavljeno v DKUM: 08.12.2023; Ogledov: 448; Prenosov: 73
Celotno besedilo (8,08 MB)