{"id":{"repo_id":"freiburg-diss","oai_identifier":"oai:freidok.uni-freiburg.de:2506"},"canonical_url":"https://search.dev.ndltd.org/etd/freiburg-diss/oai:freidok.uni-freiburg.de:2506","repository":{"repo_id":"freiburg-diss","name":"University of Freiburg","base_url":"https://freidok.uni-freiburg.de/oai/oai2.php"},"display":{"title":"Hybride von Metall-Nanopartikeln mit hochverzweigten Polyethylenimin als lösliche, abtrennbare Katalysatoren","abstract":"Nanoscale metal colloids have generated significant interest because of their unique chemical and physical surface properties. These metal particles consisting of a few hundred atoms, most of them located at the surface, are not easily stabilized in solution, and controlling their size remain a key challenge. Thermodynamically favored aggregation is usually suppressed by adsorption of low-molecular weight surfactants or linear polymers on the nanoparticle surface. Recently, motivated by the challenge of efficient nanoparticle stabilization and the concept of particle size control by means of synthesis in a confined environment, hybrids of dendrimers with metal nanoparticles have been investigated. Whereas the ideally perfectly branched dendrimers are tedious to prepare, which is a major drawback of using them as stabilizers, hyperbranched polymers, which possess a randomly branched topology, can be prepared in a controlled fashion in one step syntheses. <br>The aim of this work was the synthesis of hybrids of metal particles with hyperbranched amphiphilic polyethylenimine. Amphiphilic polyethylenimine-amides with a hyperbranched polyamine core and an apolar lypophilic alkyl chain periphery were obtained by amidation of PEI with carboxylic acids. With carbonyldiimidazole activated acids, the primary amine end groups can be reacted completely selectively. <br>PEI-amide stabilized silver-, palladium -, and rhodium dispersions can be prepared by reduction of metal salts or decomposition of metal precursors in presence of the hydrophobically modified PEI. Ag nanoparticles were obtained with H2, CO, Li[BH(C2H5)3] and hydrazine as reducing agents. The structure of Ag nanoparticles templated by polymers based on different core molecular weights (PEI Mw 5,000 g mol-1 and 25,000 g mol-1) and having the same degree of derivatization was studied by SANS. Measurements at different concentrations revealed that the neat polymer is present as non-aggregated unimolecular micelles for a polymer based on a Mw 25,000 g mol-1 core, and that silver particles are stabilized by a single polymer molecule. For a polymer based on a Mw 5,000 g mol-1 core, some aggregation occurs upon loading with the silver salt (AgNO3) and particle formation. The Ag dispersions showed antimicrobial properties. Pd nanoparticles were prepared and studied as catalysts for the hydrogenation of cyclohexene as a model reaction. The dispersions displayed low activities compared to Pd on charcoal, and to amphiphilic polyester-polyol stabilized nanoparticles of similar size. Coordination of the N-containing functional groups may block surface sites. Rhodium dispersions stabilized by PEI-amide were studied as catalysts for hydroformylation of 1-hexene. By comparison to rhodium(I) complexes as catalyst precursors (in the presence of polymer), a similar reaction profile, in terms of the gas consumption over time, was observed. The selectivity of the colloid is somewhat higher for hydrogenation and hydroformylation by-products.The effect of the reaction conditions was studied. Catalytic activities increased with pressure (in the range 10-50 bar, 120°C) and temperature (80 to 120°C, 50 bar). The catalyst could be recycled by dialysis. Upon repeated use, a ca. 25% reduction in activity was observed, which can be due to rhodium losses during recovery.","abstract_html":"Nanoscale metal colloids have generated significant interest because of their unique chemical and physical surface properties. These metal particles consisting of a few hundred atoms, most of them located at the surface, are not easily stabilized in solution, and controlling their size remain a key challenge. Thermodynamically favored aggregation is usually suppressed by adsorption of low-molecular weight surfactants or linear polymers on the nanoparticle surface. Recently, motivated by the challenge of efficient nanoparticle stabilization and the concept of particle size control by means of synthesis in a confined environment, hybrids of dendrimers with metal nanoparticles have been investigated. Whereas the ideally perfectly branched dendrimers are tedious to prepare, which is a major drawback of using them as stabilizers, hyperbranched polymers, which possess a randomly branched topology, can be prepared in a controlled fashion in one step syntheses. &lt;br&gt;The aim of this work was the synthesis of hybrids of metal particles with hyperbranched amphiphilic polyethylenimine. Amphiphilic polyethylenimine-amides with a hyperbranched polyamine core and an apolar lypophilic alkyl chain periphery were obtained by amidation of PEI with carboxylic acids. With carbonyldiimidazole activated acids, the primary amine end groups can be reacted completely selectively. &lt;br&gt;PEI-amide stabilized silver-, palladium -, and rhodium dispersions can be prepared by reduction of metal salts or decomposition of metal precursors in presence of the hydrophobically modified PEI. Ag nanoparticles were obtained with H2, CO, Li[BH(C2H5)3] and hydrazine as reducing agents. The structure of Ag nanoparticles templated by polymers based on different core molecular weights (PEI Mw 5,000 g mol-1 and 25,000 g mol-1) and having the same degree of derivatization was studied by SANS. Measurements at different concentrations revealed that the neat polymer is present as non-aggregated unimolecular micelles for a polymer based on a Mw 25,000 g mol-1 core, and that silver particles are stabilized by a single polymer molecule. For a polymer based on a Mw 5,000 g mol-1 core, some aggregation occurs upon loading with the silver salt (AgNO3) and particle formation. The Ag dispersions showed antimicrobial properties. Pd nanoparticles were prepared and studied as catalysts for the hydrogenation of cyclohexene as a model reaction. The dispersions displayed low activities compared to Pd on charcoal, and to amphiphilic polyester-polyol stabilized nanoparticles of similar size. Coordination of the N-containing functional groups may block surface sites. Rhodium dispersions stabilized by PEI-amide were studied as catalysts for hydroformylation of 1-hexene. By comparison to rhodium(I) complexes as catalyst precursors (in the presence of polymer), a similar reaction profile, in terms of the gas consumption over time, was observed. The selectivity of the colloid is somewhat higher for hydrogenation and hydroformylation by-products.The effect of the reaction conditions was studied. Catalytic activities increased with pressure (in the range 10-50 bar, 120°C) and temperature (80 to 120°C, 50 bar). The catalyst could be recycled by dialysis. Upon repeated use, a ca. 25% reduction in activity was observed, which can be due to rhodium losses during recovery.","abstract_has_math":false,"creators":["Tuchbreiter, Lydie"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Mecking, Stefan"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T02:22:46Z","subjects":["polyethylenimine","catalysis","hydroformylation","nanoparticles"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://freidok.uni-freiburg.de/data/2506","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Mecking, Stefan"]},{"key":"dc:creator","label":"Author","values":["Tuchbreiter, Lydie"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:type","label":"Dc Type","values":["DoctoralThesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["polyethylenimine","catalysis","hydroformylation","nanoparticles"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Nanoscale metal colloids have generated significant interest because of their unique chemical and physical surface properties. These metal particles consisting of a few hundred atoms, most of them located at the surface, are not easily stabilized in solution, and controlling their size remain a key challenge. Thermodynamically favored aggregation is usually suppressed by adsorption of low-molecular weight surfactants or linear polymers on the nanoparticle surface. Recently, motivated by the challenge of efficient nanoparticle stabilization and the concept of particle size control by means of synthesis in a confined environment, hybrids of dendrimers with metal nanoparticles have been investigated. Whereas the ideally perfectly branched dendrimers are tedious to prepare, which is a major drawback of using them as stabilizers, hyperbranched polymers, which possess a randomly branched topology, can be prepared in a controlled fashion in one step syntheses. <br>The aim of this work was the synthesis of hybrids of metal particles with hyperbranched amphiphilic polyethylenimine. Amphiphilic polyethylenimine-amides with a hyperbranched polyamine core and an apolar lypophilic alkyl chain periphery were obtained by amidation of PEI with carboxylic acids. With carbonyldiimidazole activated acids, the primary amine end groups can be reacted completely selectively. <br>PEI-amide stabilized silver-, palladium -, and rhodium dispersions can be prepared by reduction of metal salts or decomposition of metal precursors in presence of the hydrophobically modified PEI. Ag nanoparticles were obtained with H2, CO, Li[BH(C2H5)3] and hydrazine as reducing agents. The structure of Ag nanoparticles templated by polymers based on different core molecular weights (PEI Mw 5,000 g mol-1 and 25,000 g mol-1) and having the same degree of derivatization was studied by SANS. Measurements at different concentrations revealed that the neat polymer is present as non-aggregated unimolecular micelles for a polymer based on a Mw 25,000 g mol-1 core, and that silver particles are stabilized by a single polymer molecule. For a polymer based on a Mw 5,000 g mol-1 core, some aggregation occurs upon loading with the silver salt (AgNO3) and particle formation. The Ag dispersions showed antimicrobial properties. Pd nanoparticles were prepared and studied as catalysts for the hydrogenation of cyclohexene as a model reaction. The dispersions displayed low activities compared to Pd on charcoal, and to amphiphilic polyester-polyol stabilized nanoparticles of similar size. Coordination of the N-containing functional groups may block surface sites. Rhodium dispersions stabilized by PEI-amide were studied as catalysts for hydroformylation of 1-hexene. By comparison to rhodium(I) complexes as catalyst precursors (in the presence of polymer), a similar reaction profile, in terms of the gas consumption over time, was observed. The selectivity of the colloid is somewhat higher for hydrogenation and hydroformylation by-products.The effect of the reaction conditions was studied. Catalytic activities increased with pressure (in the range 10-50 bar, 120°C) and temperature (80 to 120°C, 50 bar). The catalyst could be recycled by dialysis. Upon repeated use, a ca. 25% reduction in activity was observed, which can be due to rhodium losses during recovery.","Metallkolloide im Nanometerbereich (1-10 nm) zeichnen sich in der Katalyse durch charakteristische Eigenschaften wie höhere Stabilität im Vergleich zu homogenen Katalysatoren und die Möglichkeit den Katalysator zurück zu gewinnen aus. Obwohl sie auf Grund ihrer einzigartigen chemischen und physikalischen Eigenschaften schon seit längerer Zeit im Mittelpunkt des Forschungsinteresses stehen, stellen sowohl Stabilisierung als auch Kontrolle der Partikelgröße während ihrer Synthese immer noch eine große Herausforderung dar. Der Einsatz von Dendrimeren erlaubt eine Größensteuerung der Metall-Nanopartikel bei guter Stabilisierung. Dendrimere zeichnen sich durch einen perfekt verzweigten Aufbau aus. Ihre Synthese ist allerdings oftmals zeit- und kostenintensiv. Demgegenüber ist die kontrollierte Herstellung (statistisch verzweigter) hyperverzweigter Polymere vergleichsweise einfach durchzuführen. <br>Ziel der Dissertation war die Synthese von Metall-Nanopartikeln auf Basis amphiphiler hyperverzweigter Polyethylenimine und die Untersuchung sowohl ihrer katalytischen Aktivität als auch ihrer Rückgewinnung. Dazu wurde hyperverzweigtes Polyethylenimin mit langkettigen Carbonsäuren durch Amidierung hydrophob modifiziert. Das Polymer mit einem hydrophilen Polyaminkern und einer apolaren lipophilen Peripherie wurde dadurch löslich in apolaren Lösungsmitteln wie Toluol. Mittels Einsatz von Carbonyldiimidazol-aktivierten Carbonsäuren gelang eine vollständige selektive Amidierung der primären Amingruppen. Auf Basis hyperverzweigter Polyethylenimine konnten Silber-Nanopartikel durch den Einsatz von H2, CO, Li[BH(C2H5)3] oder Hydrazin als Reduktionsmittel in Toluol dargestellt werden. Die Struktur der erhaltenen Silber-Nanopartikel stabilisiert mit Polyethylenimin unterschiedlichem Molekulargewichts (Mw 5.000 g mol-1 und Mw 25.000 g mol-1) wurden mit Kleinwinkelneutronenstreuung (SANS) in Benzol untersucht. Messungen bei unterschiedlichen Konzentrationen konnten zeigen, dass Polyethylenimin Mw 25.000 g mol-1 nicht-aggregiert als unimolekulare Mizellen vorliegt und das bei den entsprechenden Silber-Nanopartikeln ein Metallpartikel von einem Polymermolekül stabilisiert wird. Dagegen führte die Reduktion von AgNO3 in Gegenwart von Polyethylenimin Mw 5.000 g mol-1 zu kleinen Aggregaten der Silber-Nanopartikel. Die antimikrobiellen Eigenschaften der Silber-Dispersionen konnten bestätigt werden. Auf Grund der hydrophoben Peripherie des amphiphilen Polymers wurde das Abwaschen der Silberatome durch die Pufferlösung verhindert. Kolloidal stabile Palladium-Nanopartikel wurden durch Reduktion von Pd(II)-Verbindungen mit H2, CO oder Li[BH(C2H5)3] dargestellt und für die Hydrierung von Cyclohexen als Modelreaktion eingesetzt. Die Dispersion zeigte im Vergleich zu Pd-C und Paladium-Nanopartikeln stabilisiert mit veresterten hyperverzweigten Polyglycerinen vergleichbarer Partikelgröße eine niedrigere katalytische Aktivität (657 TO h-1 bzw. 130 TO h-1). Die Komplexierung der N-funktionellen Einheiten könnte den Zugang vom Substrat zu der Oberfläche der Partikel vermindern. Des Weiteren wurden mit amidiertem Polyethylenimin stabilisierte Rhodium-Dispersionen als Katalysatoren für die Hydroformylierung von 1-Hexen untersucht. Die Rhodium-Dispersionen zeigten im Vergleich zu Rh(I)-Komplexen als Katalysator-Precursor in Gegenwart von amidiertem Polyethylenimin eine ähnliche katalytische Reaktionskinetik und führten aber zu einem leicht höheren Anteil von Hydrierungs- und Isomerisierungsprodukten. Bei 80°C und 90 bar H2/CO (1:1) wurde eine optimierte Selektivität bezüglich Hydroformulierungsprodukten von 96% und ein optimiertes n-Heptanal/2-Methylhexanal/2-Ethylpentanal-Verhältnis von 1:0.63:0.08 beobachtet. Variationen des Druck- (10-50 bar, 120°C) sowie des Temperaturbereichs (80-120°C, 50bar) führte bei jeweiliger Erhöhung wie erwartet zu höheren Aktivitäten. Der wiederholte Einsatz der Kolloide in der Hydroformylierung nach Abtrennung der niedermolekularen Substrate durch Dialyse war möglich. Es wurde eine Abnahme der Aktivität von 25% beobachtet. Dies könnte auf einen Katalysatorverlust während der Dialyse zurückzuführen sein."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Hybride von Metall-Nanopartikeln mit hochverzweigten Polyethylenimin als lösliche, abtrennbare Katalysatoren","Hybrids of metal nanoparticles and amphiphilic hyperbranched polyethylenimine used as soluble separable catalysts"]}]}],"canonical_facts":{"dc:contributor":["Mecking, Stefan"],"dc:creator":["Tuchbreiter, Lydie"],"dc:description.abstract":["Nanoscale metal colloids have generated significant interest because of their unique chemical and physical surface properties. These metal particles consisting of a few hundred atoms, most of them located at the surface, are not easily stabilized in solution, and controlling their size remain a key challenge. Thermodynamically favored aggregation is usually suppressed by adsorption of low-molecular weight surfactants or linear polymers on the nanoparticle surface. Recently, motivated by the challenge of efficient nanoparticle stabilization and the concept of particle size control by means of synthesis in a confined environment, hybrids of dendrimers with metal nanoparticles have been investigated. Whereas the ideally perfectly branched dendrimers are tedious to prepare, which is a major drawback of using them as stabilizers, hyperbranched polymers, which possess a randomly branched topology, can be prepared in a controlled fashion in one step syntheses. <br>The aim of this work was the synthesis of hybrids of metal particles with hyperbranched amphiphilic polyethylenimine. Amphiphilic polyethylenimine-amides with a hyperbranched polyamine core and an apolar lypophilic alkyl chain periphery were obtained by amidation of PEI with carboxylic acids. With carbonyldiimidazole activated acids, the primary amine end groups can be reacted completely selectively. <br>PEI-amide stabilized silver-, palladium -, and rhodium dispersions can be prepared by reduction of metal salts or decomposition of metal precursors in presence of the hydrophobically modified PEI. Ag nanoparticles were obtained with H2, CO, Li[BH(C2H5)3] and hydrazine as reducing agents. The structure of Ag nanoparticles templated by polymers based on different core molecular weights (PEI Mw 5,000 g mol-1 and 25,000 g mol-1) and having the same degree of derivatization was studied by SANS. Measurements at different concentrations revealed that the neat polymer is present as non-aggregated unimolecular micelles for a polymer based on a Mw 25,000 g mol-1 core, and that silver particles are stabilized by a single polymer molecule. For a polymer based on a Mw 5,000 g mol-1 core, some aggregation occurs upon loading with the silver salt (AgNO3) and particle formation. The Ag dispersions showed antimicrobial properties. Pd nanoparticles were prepared and studied as catalysts for the hydrogenation of cyclohexene as a model reaction. The dispersions displayed low activities compared to Pd on charcoal, and to amphiphilic polyester-polyol stabilized nanoparticles of similar size. Coordination of the N-containing functional groups may block surface sites. Rhodium dispersions stabilized by PEI-amide were studied as catalysts for hydroformylation of 1-hexene. By comparison to rhodium(I) complexes as catalyst precursors (in the presence of polymer), a similar reaction profile, in terms of the gas consumption over time, was observed. The selectivity of the colloid is somewhat higher for hydrogenation and hydroformylation by-products.The effect of the reaction conditions was studied. Catalytic activities increased with pressure (in the range 10-50 bar, 120°C) and temperature (80 to 120°C, 50 bar). The catalyst could be recycled by dialysis. Upon repeated use, a ca. 25% reduction in activity was observed, which can be due to rhodium losses during recovery.","Metallkolloide im Nanometerbereich (1-10 nm) zeichnen sich in der Katalyse durch charakteristische Eigenschaften wie höhere Stabilität im Vergleich zu homogenen Katalysatoren und die Möglichkeit den Katalysator zurück zu gewinnen aus. Obwohl sie auf Grund ihrer einzigartigen chemischen und physikalischen Eigenschaften schon seit längerer Zeit im Mittelpunkt des Forschungsinteresses stehen, stellen sowohl Stabilisierung als auch Kontrolle der Partikelgröße während ihrer Synthese immer noch eine große Herausforderung dar. Der Einsatz von Dendrimeren erlaubt eine Größensteuerung der Metall-Nanopartikel bei guter Stabilisierung. Dendrimere zeichnen sich durch einen perfekt verzweigten Aufbau aus. Ihre Synthese ist allerdings oftmals zeit- und kostenintensiv. Demgegenüber ist die kontrollierte Herstellung (statistisch verzweigter) hyperverzweigter Polymere vergleichsweise einfach durchzuführen. <br>Ziel der Dissertation war die Synthese von Metall-Nanopartikeln auf Basis amphiphiler hyperverzweigter Polyethylenimine und die Untersuchung sowohl ihrer katalytischen Aktivität als auch ihrer Rückgewinnung. Dazu wurde hyperverzweigtes Polyethylenimin mit langkettigen Carbonsäuren durch Amidierung hydrophob modifiziert. Das Polymer mit einem hydrophilen Polyaminkern und einer apolaren lipophilen Peripherie wurde dadurch löslich in apolaren Lösungsmitteln wie Toluol. Mittels Einsatz von Carbonyldiimidazol-aktivierten Carbonsäuren gelang eine vollständige selektive Amidierung der primären Amingruppen. Auf Basis hyperverzweigter Polyethylenimine konnten Silber-Nanopartikel durch den Einsatz von H2, CO, Li[BH(C2H5)3] oder Hydrazin als Reduktionsmittel in Toluol dargestellt werden. Die Struktur der erhaltenen Silber-Nanopartikel stabilisiert mit Polyethylenimin unterschiedlichem Molekulargewichts (Mw 5.000 g mol-1 und Mw 25.000 g mol-1) wurden mit Kleinwinkelneutronenstreuung (SANS) in Benzol untersucht. Messungen bei unterschiedlichen Konzentrationen konnten zeigen, dass Polyethylenimin Mw 25.000 g mol-1 nicht-aggregiert als unimolekulare Mizellen vorliegt und das bei den entsprechenden Silber-Nanopartikeln ein Metallpartikel von einem Polymermolekül stabilisiert wird. Dagegen führte die Reduktion von AgNO3 in Gegenwart von Polyethylenimin Mw 5.000 g mol-1 zu kleinen Aggregaten der Silber-Nanopartikel. Die antimikrobiellen Eigenschaften der Silber-Dispersionen konnten bestätigt werden. Auf Grund der hydrophoben Peripherie des amphiphilen Polymers wurde das Abwaschen der Silberatome durch die Pufferlösung verhindert. Kolloidal stabile Palladium-Nanopartikel wurden durch Reduktion von Pd(II)-Verbindungen mit H2, CO oder Li[BH(C2H5)3] dargestellt und für die Hydrierung von Cyclohexen als Modelreaktion eingesetzt. Die Dispersion zeigte im Vergleich zu Pd-C und Paladium-Nanopartikeln stabilisiert mit veresterten hyperverzweigten Polyglycerinen vergleichbarer Partikelgröße eine niedrigere katalytische Aktivität (657 TO h-1 bzw. 130 TO h-1). Die Komplexierung der N-funktionellen Einheiten könnte den Zugang vom Substrat zu der Oberfläche der Partikel vermindern. Des Weiteren wurden mit amidiertem Polyethylenimin stabilisierte Rhodium-Dispersionen als Katalysatoren für die Hydroformylierung von 1-Hexen untersucht. Die Rhodium-Dispersionen zeigten im Vergleich zu Rh(I)-Komplexen als Katalysator-Precursor in Gegenwart von amidiertem Polyethylenimin eine ähnliche katalytische Reaktionskinetik und führten aber zu einem leicht höheren Anteil von Hydrierungs- und Isomerisierungsprodukten. Bei 80°C und 90 bar H2/CO (1:1) wurde eine optimierte Selektivität bezüglich Hydroformulierungsprodukten von 96% und ein optimiertes n-Heptanal/2-Methylhexanal/2-Ethylpentanal-Verhältnis von 1:0.63:0.08 beobachtet. Variationen des Druck- (10-50 bar, 120°C) sowie des Temperaturbereichs (80-120°C, 50bar) führte bei jeweiliger Erhöhung wie erwartet zu höheren Aktivitäten. Der wiederholte Einsatz der Kolloide in der Hydroformylierung nach Abtrennung der niedermolekularen Substrate durch Dialyse war möglich. Es wurde eine Abnahme der Aktivität von 25% beobachtet. Dies könnte auf einen Katalysatorverlust während der Dialyse zurückzuführen sein."],"dc:format.medium":["application/pdf"],"dc:subject":["polyethylenimine","catalysis","hydroformylation","nanoparticles"],"dc:title":["Hybride von Metall-Nanopartikeln mit hochverzweigten Polyethylenimin als lösliche, abtrennbare Katalysatoren","Hybrids of metal nanoparticles and amphiphilic hyperbranched polyethylenimine used as soluble separable catalysts"],"dc:type":["DoctoralThesis"]},"updated_at":"2026-07-24T02:22:46Z"}