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As far as the replacement of fossil fuels with more environmentally friendly options is concerned, hydrogen is considered as the most promising source of energy. Currently, hydrogen is mainly produced through the method of methane reforming. This method requires the utilisation of catalysts made of precious metals. This master's degree thesis therefore investigates perovskite materials SmCoO3, Sm0,8Ca0,2CoO2,9, SmCo0,8Al0,2O3 and Sm0,8Ca0,2Co0,8Al0,2O2,9, which could be utilised as catalysts in the production of hydrogen by methane reforming. Methane reformation occurs on the surface of a catalyst. Therefore, it is desirable to ensure that the specific surface area of a catalyst material is as large as possible. For that reason, the aforementioned perovskite materials were prepared by two sol-gel methods, which are expected to create perovskites with large specific surface areas. It was investigated in the course of the work how the method of synthesis affects the structure and catalytic properties of individual materials. The SmCo0,8Al0,2O3 material prepared by a sol-gel synthesis with propylene oxide as a gelation agent demonstrated the best results - the measurement of catalytic activity showed that the methane conversion had achieved the value of 99%.

Content: In order to develop a sustainable and low-cost route for tanning, the stabilization of the collagen fibers of the hides with silica compounds has been investigated for many years. In this context, silica nanoparticles have been studied for application in tanning due to their small size and ability to combine with polymeric substrates. This work investigates the potentialities and limitations of the use of alkoxysilanes in leather tanning, introducing silica nanoparticles in the hides, aim for process and product innovation in leather industry. The synthesis of silica nanoparticles was carried out by a typical sol-gel Stöber process. From the silica precursor tetraethoxysilane (TEOS), ammonium hydroxide as catalyst, ethanol and water, the formation of nanoparticles dispersion takes place. Vegetable tanning process was explored by introducing the silica nanoparticles in this stage starting from pickled cattle hide. Shrinkage temperature, tensile strength, softness and color fastness to light were evaluated in the leather samples. The results achieved show that the tanning experiment with only silica, without other tanning agent, did not reach the minimum shrinkage temperature required to be labeled as tanned leather. Conversely, in the presence of vegetable tannin, the shrinkage temperature reached 80°C. The physical-mechanical properties indicated that the enhanced on the tensile strength of vegetable leathers with nanosilica was about 50% and their softness was not affected by the introduction of silica. A lighter colored leather was generated with silica but less stable to light. The tanning chemistry involving silica nanoparticles and collagen is complex, therefore, more studies are needed to explore the influence of silanes on hide stabilization. Take-Away: The physical-mechanical properties indicated an increase on the tensile strength of vegetable leather. Silica did not affected the softness of the leather. A lighter colored leather was generated with the addition of the silica nanoparticles in vegetable tanning.

Oxygen barrier coatings have the potential to greatly extend the lifetime of certain food products by incorporating them into existing food packaging. Present technologies face definite challenges of maintaining high performance, while attaining simple and inexpensive preparation methods. The oxygen barrier effect obtained with these coatings is also susceptible to a plasticization effect when exposed to high humidity, since water vapor molecules are readily soluble in typically hydrophilic resins. In this work, we demonstrate a 1 – 2 micron thick oxygen barrier coating, prepared on a 12 micron poly(ethylene terephthalate) substrate, that has oxygen transmission rates as low as 1.44 cc m-2 day-1 under standard conditions and can maintain similar oxygen barrier performance at high humidity. This degree of oxygen barrier meets the standard of 1 – 10 cc m-2 day-1 established for food packaging applications. The coating is prepared through use of sol-gel chemistry between poly(vinyl alcohol) and vinyltrimethoxsilane molecules, which form a strong network resin through hydrolysis and condensation reactions. The formulation of these oxygen barrier coatings allows for variability of solids percentage and viscosity without significant change in performance. The ability to scale up the preparation of these coated films was tested successfully on an industrial flexographic printing press.

This thesis deals with fabrication and optimization of lead-free piezoceramics based on (Ba0,85Ca0,15Zr0,1Ti0,9)O3 (BCZT). The BCZT precursor powder was synthesized by sol-gel method. Dependence of relative density, microstructure, phase structure and piezoelectric properties on the sintering temperature in a range from 1300–1500 °C was studied on disc shaped samples, which were prepared by cold isostatic pressing (CIP) using pressure of 700 MPa. It was found, that sintering at 1300 and 1350 °C leads to ceramics with fine-grain microstructure, which exhibits poor piezoelectric properties (d*33 = 50 pC·N1 and 65 pC·N1, respectively). The highest value of piezoelectric charge coefficient was obtained by sintering at 1500 °C (d*33 = 390 pC·N1). Furthermore, BCZT thick films were prepared by tape casting. The composition of the ceramic slurry was optimized and various sintering techniques were tested to obtain completely flat films of BCZT ceramics. The correct sintering configuration has not been found. The least deformation of the films was achieved when the samples were sintered hung on the ZrO2 rod. The highest value of d*33 for BCZT films was measured when the sample was sintered at 1400 °C with the dwell time for 4 h (d*33 = 340 pC·N1).

Aligned arrays of nanostructures has recently attracted great interest because of their unique properties and potential use in a broad range of technological applications. The nanostructures can be employed when it is essential to create large surface on a small area in electronic device as sensor technology or energetics e.g. solar panels. One of the simplest and low-cost methods of fabricating nanostructures is template-assisted electrochemical deposition. This method also enables good control over the nanostructure dimensions and can be used to deposit a wide range of materials. The proposed method consists of two steps. At first, a non-conductive nanoporous template has to be created and then nanostructures are formed by electrodeposition into the template which is coated with a metal on one of its sides or placed on a metal surface.

INTRODUCTION Increasing age of population is a great success of numerous breakthroughs in life science and improved health care. For a child born in 2015, for example, an average global life expectancy of meanwhile 71.4 years is assumed which increased by around 8% in the last decade [1]. In accordance with enhanced life expectancy, however, age-related health problems continuously rise. In this regard, the gap between patients awaiting transplantation and appropriate donors consequently will get larger in the future [2]. To this end, there is a need for new strategies in regenerative medicine [3]. Biomaterial matrices were developed to foster tissue regeneration by mimicking the key characteristics of the extracellular matrix (ECM) [4]. Modern biomaterial research focuses on 3D scaffolds, which can be adequately adapted toward specific requirements of the target tissue [5]. In this regard, flexible material platforms are wanted, whose properties can be adjusted over a wide range and independently of each other [6]. In this context, the macromer-based material concept is promising due to the high flexibility of macromers in chemical design and processability [7]. Macromers are reactive oligo- or polymeric molecules which act as monomers and can therefore be polymerized/cross-linked into a polymeric network [8]. The key principle of this approach is the synthesis of chemically well-defined structures which allows for a more precise control over the resulting properties of the cross-linked polymeric network when compared to conventional polymers. For example, macromer chemistry can be adjusted in terms of chemical macromer composition, valence, content of cross-linkable functionalities and molecular weight. The versatility of macromer-derived materials greatly increases when different macromer types are combined which potentially enables precise material tunability on multiple levels. The design flexibility of macromer-based networks motivated the investigation of two different macromer-based material concepts with regard to macromer processability and material adjustability. The following objectives were proposed: 1) To synthesize two sets of biodegradable, multi-valent macromers by using free-radical polymerization and ring-opening polymerization combined with established activation strategies. The synthesis setups will be tuned toward high macromer yields which will be required for processing into biomaterials with relevant sizes. 2) To physico-chemically characterize oligomeric macromers with regard to chemical composition, molecular weight and reactivity in order to yield well-defined macromer structures. NMR spectroscopy, gel permeation chromatography (GPC) and wet chemistry will be applied. 3) To characterize macromer processability into covalently cross-linked hybrid matrices. This work will focus on a soft macromer-cross-linked gelatin-derived hydrogel system for versatile biomedical applications as well as a rigid macromer/sol-gel glass hybrid material for hard tissue regeneration. Sets of different formulations will be investigated in order to characterize the range of macromer processability and to establish structure-property relationships. 4) To investigate strategies for the adjustment of material porosity. Besides the adaption via cross-linking density, porogen-leaching and 3D-printing approaches will be followed in order to introduce macroporosity and to enable a decoupling of porosity and chemical (nano)structure of the cross-linked network. 5) To determine key material properties relevant for regenerative applications, including mechanical properties by compression tests and oscillation rheology, in vitro matrix degradability, as well as material cytocompatibility in indirect and direct contact experiments. 6) To identify strategies for covalent functionalization of the hybrid materials. Post-fabrication functionalization via specifically introduced chemical functionalities is favored as it enables effective material decoration (almost) independent of the physico-chemical matrix properties. SUMMARY OF DISSERTATION The first material concept was based on anhydride-containing macromers which can be processed into hydrogel matrices by covalent cross-linking of amine-bearing macromolecules, such as gelatin [9–11]. The innovative aspect of this work was to decouple material functionalization from the physico-chemical properties of the cross-linked hydrogel network. To this end, a second chemical functionality was introduced which remained reactive in the hydrogel state and was therefore available for covalent post-fabrication functionalization strategies. Specifically, dual-functional macromers were synthesized by free-radical polymerization of maleic anhydride (MA) with diacetone acrylamide (DAAm) and pentaerythritol diacrylate monostearate (PEDAS) to yield oligo(PEDAS-co-DAAm-co-MA) (oPDMA) [12]. Amphiphilic oligomers (molecular weight (Mn) < 7.5 kDa) with anhydride contents of 7-20% were obtained. Fractions of chemically intact anhydrides of around 70% enables effective cross-linking with low molecular-weight gelatinous peptides (Collagel® type B, 11 kDa). Rigid two-component hydrogels (elastic modulus (E) = 4-13 kPa) with adjustable composition and physicochemical properties were formed. Reactivity of the incorporated methyl ketone functionality toward hydrazides and hydrazines was shown on the macromer level and in the cross-linked hydrogel by different strategies. Firstly, pre-fabricated hydrogels were successfully reinforced by secondary cross-linking with adipic acid dihydrazide (ADH). Secondly, pH-dependent immobilization of 2,4-dinitrophenylhydrazine (DNPH) to acid-soluble macromer derivatives as well as cross-linked oPDMA/COL matrices was demonstrated. Thirdly, reversible immobilization of a fluorescent hydrazide (AFH) was shown which was controlled by hydrogel ketone content, hydrazide ligand concentration and medium pH. This triple-tunability of hydrazide immobilization holds promise for adjustable and cost-effective hydrogel modification. Lastly, proof-of-concept experiments with hydrazido-functionalized hyaluronan (ATTO-hyHA) demonstrated the potential for covalent post-fabrication hydrogel decoration with ECM components. Hydrogel cytocompatibility was demonstrated and the introduction of DAAm into the hydrogel system resulted in superior cell material interactions when compared with previously established analogous ketone-free gels [13]. Limited ability of cells to migrate into deeper regions of these macromer-cross-linked gelatin-based gels further motivated the investigation of two different strategies to enhance hydrogel porosity [10,14]. On the one hand, the introduction of macropores was attempted by hydrogel fabrication in presence of poly(ethylene glycol) (Mn = 8000 Da, P8k). This polymer acted as porogen by phase separation during hydrogel formation. It was found that P8k was effectively extracted from the cross-linked matrix, while physico-chemical hydrogel properties remained unchanged. The second approach aimed at increasing mesh size of the cross-linked network by using hydrogel building blocks with increased molecular weights. In particular, high molecular-weight gelatin (160 Bloom, G160) was cross-linked by macromers with low MA content. Homogeneous and mechanically stable hydrogels were obtained and physico-chemical properties were determined. Successful optimization of hydrogel porosity was functionally shown by enhanced cell migration and improved release profile of incorporated nanoparticles [15]. In the second macromer-based material, hydrolytically degradable multi-armed macromers were covalently introduced into a tetraethoxysilane(TEOS)-derived silica sol in order to address the insufficient degradability of glass-based materials [16]. In detail, oligo(D,L-lactide) units were introduced into three- (TMPEO, Tx) and four-armed (PETEO, Px) ethoxylated alcohols by ring-opening polymerization, followed by activation with 3-isocyanatopropyltriethoxysilane (ICPTES) to yield TxLAy-Si and PxLAy-Si macromers [17,18]. A series of 18 oligomers (Mn: 1100-3200 Da) with different degrees of ethoxylation and varying length of oligoester units was synthesized. Applicability of a previously established indirect rapid prototyping method enabled fabrication of macromer/sol-gel-glass-derived class II hybrid scaffolds with controlled porosity [19]. Successful processability of a total of 85 different hybrid scaffold formulations allowed for identification of relevant structure-property relationships. In vitro degradation was analyzed over 12 months and a continuous linear weight loss (0.2-0.5 wt%/d) was detected which was controlled by oligo(lactide) content and matrix hydrophilicity. Compressive strength (2-30 MPa) and compressive modulus (44-716 MPa) were determined and total content, oligo(ethylene oxide) content, oligo(lactide) content and molecular weight of the oligomeric cross-linkers as well as material porosity were identified as the main factors determining hybrid mechanics by multiple linear regression. Cell migration into the entire scaffold pore network was indicated in cell culture experiments with human adipose tissue-derived stem cells (hASC) and continuous proliferation over 14 days was found. Overall, two macromer-based material platforms were established in which material versatility was realized by three main principles: I) synthesis of macromers with different chemical composition, II) combination of macromers with a second oligomeric building block, and III) flexible processability of these dual-component hybrid formulations into porous scaffold materials. Precise adjustability of material properties as demonstrated in both concepts offers potential for application of these hybrid materials for a wide range of regenerative purposes. REFERENCES (1) World Health Statistics of the WHO. http://www.who.int/gho/publications/world_health_statistics/en/ 2017. (2) OPTN/UNOS Public Comment. https://optn.transplant.hrsa.gov/ 2017. (3) Puppi, D.; Chiellini, F.; Piras, a. M. M.; Chiellini, E. Prog. Polym. Sci. 2010, 35 (4), 403–440. (4) Patterson, J.; Martino, M. M.; Hubbell, J. A. Mater. Today 2010, 13 (1–2), 14–22. (5) Picke, A.-K.; Salbach-Hirsch, J.; Hintze, V.; Rother, S.; Rauner, M.; Kascholke, C.; Möller, S.; Bernhardt, R.; Rammelt, S.; Pisabarro, M. T.; Ruiz-Gómez, G.; Schnabelrauch, M.; Schulz-Siegmund, M.; Hacker, M. C.; Scharnweber, D.; Hofbauer, C.; Hofbauer, L. C. Biomaterials 2016, 96, 11–23. (6) Loth, R.; Loth, T.; Schwabe, K.; Bernhardt, R.; Schulz-Siegmund, M.; Hacker, M. C. Acta Biomater. 2015, 26, 82–96. (7) DeForest, C. A.; Anseth, K. S. Nat. Chem. 2011, 3 (12), 925–931. (8) Nic, M.; Jirát, J.; Košata, B.; Jenkins, A.; McNaught, A.; Wilkinson, A. IUPAC, Research Triangle Park, NC 2014. (9) Loth, T.; Hennig, R.; Kascholke, C.; Hötzel, R.; Hacker, M. C. React. Funct. Polym. 2013, 73 (11), 1480–1492. (10) Loth, T.; Hötzel, R.; Kascholke, C.; Anderegg, U.; Schulz-Siegmund, M.; Hacker, M. C. Biomacromolecules 2014, 15 (6), 2104–2118. (11) Kohn, C.; Klemens, J. M.; Kascholke, C.; Murthy, N. S.; Kohn, J.; Brandenburger, M.; Hacker, M. C. Biomater. Sci. 2016, 4, 1605–1621. (12) Kascholke, C.; Loth, T.; Kohn-Polster, C.; Möller, S.; Bellstedt, P.; Schulz-Siegmund, M.; Schnabelrauch, M.; Hacker, M. C. Biomacromolecules 2017, 18 (3), 683–694. (13) Sülflow, K.; Schneider, M.; Loth, T.; Kascholke, C.; Schulz-Siegmund, M.; Hacker, M. C.; Simon, J.-C.; Savkovic, V. J. Biomed. Mater. Res. A 2016, 104 (12), 3115–3126. (14) Loth, T. Diss. Univ. Leipzig, Fak. für Biowissenschaften, Pharm. und Psychol. 2016. (15) Schwabe, K.; Ewe, A.; Kohn, C.; Loth, T.; Aigner, A.; Hacker, M. C.; Schulz-Siegmund, M. Int. J. Pharm. 2017, 526 (1–2), 178–187. (16) Rahaman, M. N.; Day, D. E.; Sonny Bal, B.; Fu, Q.; Jung, S. B.; Bonewald, L. F.; Tomsia, A. P. Acta Biomater. 2011, 7 (6), 2355–2373. (17) Schulze, P.; Flath, T.; Dörfler, H.-M.; Schulz-Siegmund, M.; Hacker, M.; Hendrikx, S.; Kascholke, C.; Gressenbuch, M.; Schumann, D. Ger. Pat. No. DE102014224654A1 2016. (18) Kascholke, C.; Hendrikx, S.; Flath, T.; Kuzmenka, D.; Dörfler, H.-M.; Schumann, D.; Gressenbuch, M.; Schulze, F. P.; Schulz-Siegmund, M.; Hacker, M. C. Acta Biomater. 2017, 63, 336–349. (19) Hendrikx, S.; Kascholke, C.; Flath, T.; Schumann, D.; Gressenbuch, M.; Schulze, P.; Hacker, M. C.; Schulz-Siegmund, M. Acta Biomater. 2016, 35, 318–329.

Unter Nutzung des Sol-Gel-Prozess von Siliciumalkoxiden wurden dünne Schichten präpariert. Um eine Funktionalisierung derartiger SiO2-Schichten zu erhalten, wurden einem auf Tetraethoxysilan basierenden Sol Aldehyde, Hydroxycarbonsäuren bzw. Amino-carbonsäuren zugesetzt. Alternativ zu Additiven wurden Alkyltriethoxysilane eingesetzt. Neue azomethinhaltige Siliciumprecursoren wurden synthetisiert und direkt oder im Gemisch mit Tetraethoxysilan hydrolisiert und auf ihre Eignung hinsichtlich der Schichtpräparation getestet. Der Einfluss der Modellsubstanzen auf die Kinetik des Sol-Gel-Prozesses, die Schichtzusammensetzung und die Schichteigenschaften, wird durch die Kombination spektroskopischer und oberflächen-analytischer Methoden aufgeklärt. Für eine Prüfung der erzielten Funktionalisierung wurden die verschieden modifizierten Solsysteme zur Immobilisierung des Enzyms Glucose-Oxidase eingesetzt und die erzielten Enzymaktivitäten systematisch verglichen.

Superacidic mesoporous materials containing covalently embedded PTA were synthesized by sol-gel method. Tetraethyl orthosilicate (TEOS) and phosphotungstic acid (PTA) were used as precursors in the synthesis, ionic and nonionic surfactants were used as pore-forming agents, the reaction proceeded in acidic media. TEM images revealed mesoporous structure with embedded PTA clusters. FT-IR spectra of obtained materials contained characteristic bands of PTA at 957 cm-1. Synthesized catalysts had high BET surface area and high concentration of acidic sites. Alkylation of 1,3,5-trimethylbenzene by 1-decene demonstrated high catalytic activity. The catalyst obtained with Pluronic P123 as a template was the most effective and resulted in highest conversion of 1-decene into alkylated products. Covalent embedding of PTA clusters in addition to thermal and chemical stability of synthesized catalysts enabled their recyclability. Catalysts remained active during subsequent cycles of alkylation.

This thesis focuses on developing an appropriate cathode material throughnanotechnology as a key component for a promising alternative of renewable energygenerating systems, Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC).Aiming at a working cathode material for IT-SOFC, a recently reported capable oxideperovskite material has been synthesized through two different chemical methods.BaxSr1-xCoyFe1-yO3−δ (BSCF) with y =0.8 and x =0.2 was fabricated in nanocrystallineform by a novel chemical alloying approach, co-precipitation- as well as conventionalsol-gel method to produce oxide perovskites. The thermal properties, phase constituents,microstructure and elemental analysis of the samples were characterized by TG-DSC,XRD, SEM and EDS techniques respectively. Thermodynamic modeling has beenperformed using a KTH-developed software (Medusa) and Spark Plasma Sintering (SPS)has been used to obtain pellets of BSCF, preserving the nanostructure and generatingquite dense pellets for electrical conductivity measurements.The results show that the powders synthesized by solution co-precipitation have cubicperovskite-type structure with a high homogeneity and uniform distribution and meanparticle size of 50-90 nm range, while sol-gel powders are not easy to form a pure phaseand mostly the process ends up with large particle containing two or three phases.Finer resultant powder compared to sol-gel technique and earlier research works onBSCF has been achieved in this project using oxalate co-precipitation method. Topreserve nanoscaled features of BSCF powder which possess a significant increase ofelectrical conductivity due to decrease the electrical resistivity of grain boundaries, forthe sample synthesized through co-precipitation, ~92% dense pellet sintered by SPS atV1080 °C and under 50 MPa pressure and its electrical conductivity has been measuredfrom room temperature to 900 °C.Specific conductivity values were precisely measured and the maximum of 63 S.cm-1 at430 °C in air and 25 S.cm-1 at 375°C in N2 correspondingly are two times higher thanconventional BSCF implying a high pledge for nano-BSCF as a strong candidate ascathode material in IT-SOFC.