Functional Polymer Gels based on Oligomer Fluids

Polymergele, wie beispielsweise Hydrogele, die aus vernetzten Polymerketten und niedermolekularen Lösungsmitteln bestehen, wurden aufgrund der Ähnlichkeit ihrer mechanischen Eigenschaften mit denen von weichen biologischen Geweben weit verbreitet in biomedizinischen Anwendungen, flexibler Elektronik und weichen Maschinen verwendet. Das Design von Polymernetzwerken und sein Beitrag zu den Eigenschaften solcher Materialien wurden ausgiebig untersucht. Die infundierten Lösungsmittel, die die innere Struktur von Gelen stark beeinflussen würden, werden jedoch selten untersucht. Ziel dieser Dissertation ist es, eine Reihe von Lösungsmittelstrategien zur Herstellung funktioneller Polymergele bereitzustellen. In Kapitel 1 wird eine allgemeine Einführung in funktionelle Polymergele basierend auf verschiedenen Lösungsmitteln gegeben, die die verschiedenen Wahlmöglichkeiten von Lösungsmitteln für Polymergele und von den Lösungsmittelstrategien abgeleitete Funktionen abdeckt. Für die Auswahl der Lösungsmittel wurden die Herstellungsmethoden und die neuesten Entwicklungen der Polymergele auf Basis verschiedener Lösungsmittel zusammengefasst, darunter organische Lösungsmittel, ionische Flüssigkeiten, tiefeutektische Lösungsmittel und Polymerflüssigkeiten. Dann wurden die aus den Lösungsmittelstrategien abgeleiteten Funktionen diskutiert, darunter rutschige Oberflächen, Gefrierbeständigkeit oder thermische Stabilität, überlegene mechanische Eigenschaften und elektrische Leistung. In Kapitel 3.1 wurde ein Polymergelsystem auf Basis von Poly(ethylenglykol) (PEG) als Flüssigphase demonstriert. Der kritische Einfluss der Lösungsmittelnatur auf die mechanischen Eigenschaften und die Leistung von weichen Polymergelen wurde untersucht. Als elastisches Polymernetzwerk wurde ein physikalisch vernetztes Copolymer aus 2-Hydroxyethylmethacrylat und Acrylsäure gewählt. Verglichen mit dem entsprechenden Gel auf Hydrogel- oder Ethylenglykolbasis weist das PEGgel außergewöhnliche physikalische Eigenschaften auf, wie z. B. hohe Dehnbarkeit und Zähigkeit, schnelle Selbstheilung und Langzeitstabilität unter Umgebungsbedingungen. Je nach Molekulargewicht und PEG-Anteil variierte die Zugfestigkeit von PEGgelen von 0,22 MPa bis 41,3 MPa, die Bruchdehnung von 12 % bis 4336 %, der Elastizitätsmodul von 0,08 MPa bis 352 MPa und die Zähigkeit von 2,89 MJ m-3 bis 56,23 MJ m-3. Die erhaltenen Polymergele können zur Herstellung eines selbstheilenden pneumatischen Aktuators durch 3D-Druck verwendet werden. Die verbesserten mechanischen Eigenschaften des PEGgel-Systems könnten auf andere Polymernetzwerke (sowohl chemisch als auch physikalisch vernetzt) ausgedehnt werden. In Kapitel 3.2 wurden Ionen in das Lösungsmittelsystem eingeführt, um ionisches PEGgel herzustellen. Der Einbau von Ionen in PEG erhöht gleichzeitig die Festigkeit und Zähigkeit der Polymergele. Das typische ionische PEGgel besteht aus in situ gebildeten, physikalisch vernetzten Poly(2-hydroxyethylmethacrylat)-Netzwerken und PEG und weist eine hohe Leitfähigkeit (0,04 S m-1), eine ausgezeichnete elektrochemische Stabilität (> 60.000 Zyklen), eine extreme Dehnbarkeit ( bis zu 1400 %), hohe Zähigkeit (7,16 MJ m-3), schnelle Selbstheilungseigenschaft, die eine Wiederherstellung der Ionenleitfähigkeit innerhalb von Sekunden ermöglicht, sowie keine Lösungsmittelleckage auf. Mehrere Anwendungen von ionischem PEGgel wurden als (a) flexible Sensoren zur Dehnungs- oder Temperaturmessung, (b) Hautelektroden zur Aufzeichnung von Elektrokardiogrammen und (c) als robustes und sensorisches Material für pneumatische künstliche Muskeln demonstriert. In Kapitel 3.3 wurde eine In-situ-Phasentrennung im PEGgel-System unter Verwendung der Mischung aus PEG und Polypropylenglykol (PPG) als Lösungsmittel gebildet. Die phasengetrennten Polymergele wurden durch direktes Polymerisieren von 2-Hydroxyethylmethacrylat in einer Mischung aus PEG und PPG hergestellt. Die polymerisierten elastischen Netzwerke weisen eine unterschiedliche Löslichkeit in PEG (hochlöslich) und PPG (schwach löslich aufgrund des vorhandenen Methyls in der Hauptkette) auf, was zu einem makroskopisch homogenen kovalenten Netzwerk mit in-situ-Phasentrennung führt. Das resultierende phasengetrennte gel zeigt eine hohe Festigkeit (8,0 MPa), eine günstige Bruchdehnung (430 %) und eine große Zähigkeit (17,0 J m-3). Die getrennten Phasen verleihen dem Polymergel eine Formgedächtniseigenschaft, die für verschiedene weiche Maschinen in Kombination mit 3D-Druckfähigkeit verwendet werden kann. Dann wurden Ionen in das PEG/PPG-Lösungsmittel eingebaut, um eine hierarchische Verbesserung in Polymergelen zu erreichen, die von den ionischen Wechselwirkungen (Nanoebene) bis zur Phasentrennung (Mikroebene) reicht. Eine solche hierarchische Struktur verbesserte die Festigkeit und Zähigkeit von Polymergelen weiter und zeigte eine hohe Bruchfestigkeit (12,2 MPa) und Bruchenergie (54 kJ m-2). Abschließend wurde ein Ausblick auf die Herausforderungen gegeben, denen man sich bei der Entwicklung funktioneller Polymergele stellen muss. Um die Entwicklung von Polymergelen in verschiedenen Bereichen zu beschleunigen, müssen wir sowohl das Netzwerkdesign als auch die Lösungsmittelstrategien optimieren. Fortschritte auf nur einer Seite reichen nicht aus, um alle Herausforderungen zu lösen

EXPLORATORY SYNTHESIS AND CHARACTERIZATION OF NEW MIXED-FRAMEWORK CHALCOHALIDES AND OXYHALIDE AND ITS POTENTIAL APPLICATIONS FOR DILUTED MAGNETIC SEMICONDUCTOR

Due to the excellent diverse properties and performance, solid-state material with low-dimensional crystal structure has always been interested by solid-state scientists. Besides the interesting properties, the low-dimensional-structured materials are used as the platform for further research and application of semiconductor and optical devices, as well as theoretic studies. My dissertation research mainly focuses on two aspects: discovery of solids with low-dimensional crystal structure; fabrication and investigation of new materials using the discovered materials as the platform. The idea of mixed-anion-framework has been used in synthesis of novel low-dimensional-structured solid-state materials. The stereo-active Sb3+/Bi3+ chalcogenides building units and their halogen-containing derivatives have been applied for the new structure search and design. Four chalcohalides families with novel structures: CdMQ2X; CdSb2Se3Br2; InM2Q4X (M = Sb, Bi; Q = S, Se; X = Cl, Br and I); In2Bi3Se7I and one new discovered oxyhalide LiSb2O3Cl have been designed, synthesized and characterized. Two DMS systems -- Mn-doped CdBiS2Cl and CdBiSe2I with confined crystal structures have been fabricated and characterized; the ferromagnetism has been firstly observed in the discussed chemical system. Also, the correlation between magnetism and structure has been investigated and rationalized. In this thesis, the exploratory synthetic work (conceptual structure design and crystal growth), the characterization of properties (X-ray crystal structure analysis, optical, and magnetic studies) and the theoretic calculation (band structure and bond valance analysis) will be discussed in details

Hallmarks of mechanochemistry: From nanoparticles to technology

The aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references).Slovak Grant Agency VEGA 2/0009/11, 2/0043/11Slovak Agency for Science and Development APVV VV-0189-10, VV-0528-11Russian Foundation for Basic Research 10-03-00942a, 12-03-00651aMinistry of Science and Higher education in Poland CUT/c-1/DS/KWC/2008-2012, PB1T09B02330, NN209145136, NN20914893

Crystal Growth And Characterization Of Reduced Early Transition Metal Compounds Grown Via Hydrothermal And Molten Flux Methods

Interest in new and facile ways to prepare early transition metal reduced oxides has recently been increasing. In the past difficult flux techniques involving vacuum furnaces, expensive metal tubing, complicated electrolytic reduction apparatuses, were used to achieve in situ reduction of fully oxidized transition metal precursors. Often times these techniques were coupled with use of a difficult flux, such as boric acid, which is hard to remove due to its insolubility in water at room temperature. These limitations can be circumvented in multiple ways, including carefully choosing a redox neutral flux, using evacuated fused silica tubes for reaction vessels, and employing metallic reducing agents such as powered molybdenum, vanadium, or zinc. Virtually no work has been done outside the realm of flux crystal growth. Nevertheless, the hydrothermal method for crystal growth can be employed to yield hybrid materials containing reduced early transition metals. Through the successful utilization of a two-step hydrothermal method, four oxovanadium(IV) tartrates have been prepared and characterized with three out four having confirmed second harmonic generation activity and one exhibiting spin dimer magnetic behavior. Via a one step hydrothermal method involving an in situ reduction, one oxovanadium(IV) phosphate has been prepared and found to exhibit filled channels in two crystallographic directions. Using the flux method many reduced molybdenum oxides and a related material have been prepared and characterized including the following series: NaxLn1-xMoO4Ln = La, Ce, Pr,Nd, Sm, and Eu; Ln~5Mo3O16 Ln = Ce, Pr, Nd and Sm; and Ln5Mo2O12 Ln = Eu, Tb, Dy, Ho, and Er. Evidence of direct molybdenum to molybdenum bonding was in the Ln5Mo2O12 series, and all compounds were found to order antiferromagnetically. A related material, La20Mo12O63Cl4, was found to exhibit an optical band gap in the visible region and is the first example of a purely inorganic material that contains molybdenum in a trigonal prismatic coordination environment

EXPLORATORY SYNTHESIS OF NEW IRON(II,III)-CONTAINING POLYANION FRAMEWORK SOLIDS OF ELECTROCHEMICAL AND MAGNETIC INTEREST

The studies demonstrated in this dissertation were primarily focused on the synthesis, structure and property characterizations of iron(II,III) containing framework solids. The scope of this research is threefold: 1) explore new iron(II, III)-containing open framework structures in hopes of creating new materials, useful in the areas of both Li- and Na-ion battery applications; 2) synthesis and characterization of low-dimensional magnetic nanostructures exhibiting novel magnetic properties due to confined magnetic lattices; and 3) conduct structure/property correlation studies to identify the origins of any unusual physical phenomena associated with these new compounds. In the syntheses of new compounds, molten salt fluxes were utilized due to the refractory nature and low solubility of the covalent transition metal oxides, such as alkali metal chlorides and iodides. Furthermore, the use of eutectic fluxes allowed us to investigate new flux-incorporated compounds via in situ reactions (metathesis reactions). Additionally, oxyanions XO43- (X = P and As) were employed to obtain 3-D Fe-O-X frameworks. Having a poly-anion group in the structure not only increases the Fe3+ /Fe2+ redox couple (due to the inductive effect), regarding potential battery applications but also allows the synthesis of new compounds with magnetic nano-structures embedded in closed-shell, non-magnetic oxyanion matrices. The use of molten salt fluxes allowed for the discovery of several new iron(II,III)-containing phosphates and arsenates for a structure/property correlation study. Throughout, exploratory syntheses was employed with a typical reaction including various transition metal oxides (Fe2 O3 and/or FeO), main group oxides such as P4 O10 or As2 O 5 , and alkali/alkaline-earth metal oxides. High-temperature solid-state reactions in molten-salt media were utilized in the crystal growth and characterization was performed mainly using single crystal and powder X-ray diffraction. For further property characterizations, techniques and measurements such as electrochemical testing, neutron powder diffraction, magnetic susceptibility measurements, electrical conductivity measurements, electron microscopy, thermal gravimetric analysis, UV-Vis diffuse reflectance and IR were performed. The new discoveries in this dissertation, mainly, Rb0.41 FePO 4 and A3 Fe6 (XO4 )7 ; A = K, Rb, Cs and X = P and As, have shown fascinating 3-D Fe-O-X frameworks with interesting ion-exchange properties. These new compounds, based on A-Fe-O-X systems where A = larger alkali and alkaline-earth metal cations than Li-ion and these large cations, were used as templates to synthesize new open-frameworks that cannot be initially formed with Li-ions. Sr 1.25 Na1.5 Fe5 O2 (PO4 )5 , another novel open framework structure, was studied as a cathode material for sodium ion batteries due to the interesting channeled structure, see Chapter 5. Furthermore, these new structures tend to form interesting Fe-O lattices (3-D networks, 2-D sheets, 1-D chains) isolated by diamagnetic poly-anion groups which have been proven to be extremely rich concerning novel magnetic properties. Chapter 6 was aimed on the investigation of the magnetic properties of A 2 Fe2 O(AsO4 )2 ; A = K and Rb with pseudo-one-dimensional Fe-O chains. Moreover, in relation to the investigation of novel magnetic properties, a heterometallic system ( 3d-4f ) was discovered, Rb7 LnFe6 O2 (PO 4 )8 , and the magnetic properties of derivatives where Ln = Sm, Gd and Dy will be discussed. Finally, the structure/property correlations and future development of these newly synthesized compounds should fruitful for the future of battery applications and understanding of novel magnetic phenomena

HIGH TEMPERATURE SYNTHESIS AND CHARACTERIZATION OF REDUCED POLYOXOMETALATE SALT-INCLUSION SOLIDS

Herein, several new salt-inclusion solids (SISs) featuring electronically reduced Keggin polyoxometalate (POM) clusters were isolated for the first time using molten-salt high temperature (\u3e 500 oC) synthetic method. These POM-based SISs are novel all-inorganic materials featuring an integrated lattice of ionic halide salt and covalent metal oxide clusters. Due to the weak interactions at the interface between these two chemically dissimilar lattices, these POM SISs are soluble in aqueous and polar solvents. While POM compounds are well-studied and are routinely synthesized in solution, the synthetic method presented in this dissertation yielded several POM solids with interesting structures and infrequently observed, reduced oxidation states of the transition metal cations. This dissertation focuses on describing the high temperature (\u3e 500 oC), salt-inclusion synthesis of several all-inorganic, reduced polyoxometalate clusters. Four chapters with different chemical systems are presented. Chapters 3, 4, and 5 feature related Keggin-based POM compounds: namely the one electron reduced, Cs6I3Na(PMo12O40), POM compound in Chapter 3; the two electron reduced family of compounds, Cs6X2Na(PMo12O40) where X2 = Cl2, ICl, Br2, and I2 in Chapter 4; and the highly reduced family of compounds, Cs6X2M(PMo12O40) where M3+ = Ti, V, Mn, Fe and X2 = Cl2, Br2 and I2 in Chapter 5. In addition, a series of hybrid inorganic-organic compounds based on reduced polyoxovanadates (POVs) are presented in Chapter 6 where a novel method using pre-synthesized soluble POVs was used. These results demonstrate the utility of salt-inclusion chemistry in regards to water-soluble POM salts that can be used for various transformative studies of biomedical and catalytic relevance. Antibacterial tests in aqueous solution of the two electron reduced POMs (Chapter 4) show that the Staph. A. bacterial strains (SA1199, SA1199B, MRSA) are more susceptible to inhibition by the reduced POMs, presented herein, compared to their fully oxidized counterparts (e.g. Na3PMoVI12O40•2H2O). Replacing the Na+ cation in the two electron reduced POM with transition metals (Ti, V, Mn and Fe) resulted in the isostructural highly reduced family of compounds in Chapter 5. These novel POM SISs feature infinite one-dimensional (1D) transition metal-oxide chains with interlinked Keggin clusters, {-M-(PMo12O40)-}∞. These chains feature unusual square antiprismatic eight-coordinate environments of the transition metals chelated by the Keggin clusters and forming chains along the tetragonal (P4/ncc), c crystallographic direction. The unusual eight-coordination of the first-row transition metals is the first such example in an all-inorganic compound with oxo-based ligand environment. The compounds presented in this dissertation were characterized by several solid-state and solution-based characterization techniques including: single crystal and powder X-ray diffraction, biomedical properties of soluble POMs, magnetic susceptibility, spectroscopy (UV-vis and IR), electrochemical properties, and thermogravimetric analysis. The work presented in this dissertation is significant for several reasons: 1) this opens up a new method for synthesis of POM solids; 2) isolation of electronically reduced POMs is favored using the high-temperature, molten-salt method; 3) this method produced novel POM-based SISs that are otherwise unattainable using conventional methods; 4) unusual structures and local geometry (e.g. metal-oxide connectivity along c and eight-coordination of transition metals) could give rise to interesting properties, including water-soluble clusters, to be studied in the near future; 5) in regards to the solids synthesized in Chapter 6, a new understanding of the interaction between anionic POV clusters and organic ligands with respect to the nature of bonding is learned; 6) finally, the synthesis of POM SISs illustrated, once more, the versatility and utility of the salt-inclusion synthetic method

Solid state NMR spectroscopic studies of organic semiconductors for molecular electronics application

s. ArbeitGetrennte Zählungen ; Illustrationen, Diagramm

HIGH TEMPERATURE SYNTHESIS AND CHARACTERIZATION OF REDUCED POLYOXOMETALATE SALT-INCLUSION SOLIDS

Herein, several new salt-inclusion solids (SISs) featuring electronically reduced Keggin polyoxometalate (POM) clusters were isolated for the first time using molten-salt high temperature (\u3e 500 oC) synthetic method. These POM-based SISs are novel all-inorganic materials featuring an integrated lattice of ionic halide salt and covalent metal oxide clusters. Due to the weak interactions at the interface between these two chemically dissimilar lattices, these POM SISs are soluble in aqueous and polar solvents. While POM compounds are well-studied and are routinely synthesized in solution, the synthetic method presented in this dissertation yielded several POM solids with interesting structures and infrequently observed, reduced oxidation states of the transition metal cations. This dissertation focuses on describing the high temperature (\u3e 500 oC), salt-inclusion synthesis of several all-inorganic, reduced polyoxometalate clusters. Four chapters with different chemical systems are presented. Chapters 3, 4, and 5 feature related Keggin-based POM compounds: namely the one electron reduced, Cs6I3Na(PMo12O40), POM compound in Chapter 3; the two electron reduced family of compounds, Cs6X2Na(PMo12O40) where X2 = Cl2, ICl, Br2, and I2 in Chapter 4; and the highly reduced family of compounds, Cs6X2M(PMo12O40) where M3+ = Ti, V, Mn, Fe and X2 = Cl2, Br2 and I2 in Chapter 5. In addition, a series of hybrid inorganic-organic compounds based on reduced polyoxovanadates (POVs) are presented in Chapter 6 where a novel method using pre-synthesized soluble POVs was used. These results demonstrate the utility of salt-inclusion chemistry in regards to water-soluble POM salts that can be used for various transformative studies of biomedical and catalytic relevance. Antibacterial tests in aqueous solution of the two electron reduced POMs (Chapter 4) show that the Staph. A. bacterial strains (SA1199, SA1199B, MRSA) are more susceptible to inhibition by the reduced POMs, presented herein, compared to their fully oxidized counterparts (e.g. Na3PMoVI12O40•2H2O). Replacing the Na+ cation in the two electron reduced POM with transition metals (Ti, V, Mn and Fe) resulted in the isostructural highly reduced family of compounds in Chapter 5. These novel POM SISs feature infinite one-dimensional (1D) transition metal-oxide chains with interlinked Keggin clusters, {-M-(PMo12O40)-}∞. These chains feature unusual square antiprismatic eight-coordinate environments of the transition metals chelated by the Keggin clusters and forming chains along the tetragonal (P4/ncc), c crystallographic direction. The unusual eight-coordination of the first-row transition metals is the first such example in an all-inorganic compound with oxo-based ligand environment. The compounds presented in this dissertation were characterized by several solid-state and solution-based characterization techniques including: single crystal and powder X-ray diffraction, biomedical properties of soluble POMs, magnetic susceptibility, spectroscopy (UV-vis and IR), electrochemical properties, and thermogravimetric analysis. The work presented in this dissertation is significant for several reasons: 1) this opens up a new method for synthesis of POM solids; 2) isolation of electronically reduced POMs is favored using the high-temperature, molten-salt method; 3) this method produced novel POM-based SISs that are otherwise unattainable using conventional methods; 4) unusual structures and local geometry (e.g. metal-oxide connectivity along c and eight-coordination of transition metals) could give rise to interesting properties, including water-soluble clusters, to be studied in the near future; 5) in regards to the solids synthesized in Chapter 6, a new understanding of the interaction between anionic POV clusters and organic ligands with respect to the nature of bonding is learned; 6) finally, the synthesis of POM SISs illustrated, once more, the versatility and utility of the salt-inclusion synthetic method