Seminars and Events
New Architectures in Materials Chemistry
Coordinator: Eva M. Garcia Frutos
09 October 2018, 12:00 h. Sala de Seminarios, 182
Bioinspired structural design of ceramic based functional materials
University of Stuttgart, Institute for Materials Science, Stuttgart, Germany
The extraordinary combination of strength and toughness of biomaterials, which testifies nature’s highly sophisticated structural design principles, has inspired the synthesis of a wide range of advanced ceramic based nanocomposites. This approach is expected to yield novel materials with unique mechanical properties and advanced functionality. However, despite the significant progress in understanding the assembly mechanisms that are operative in biomaterial formation, the transfer of their structural organization to synthetic materials still remains a major challenge.
In this talk, I will summarize our contribution to the goal of implementing biomaterial structural organization into synthetic materials. We have developed synthesis approaches for mimicking the structure of nacre, sponge spicule and cuttlebone within functional ceramic materials. Thus we succeeded in the fabrication of thin films that display a high toughness, flexible ceramic papers, bendable ceramic scrolls, or highly porous ceramic scaffolds that reveal damping behavior superior than polyurethane foams. For these bioinspired materials, we have furthermore explored the influence of the bioinspired structural design on their mechanical performance. In addition, we have studied the actuation, electrical, and electrochemical properties of various bioinspired designed ceramic materials which are promising for energy storage and energy conversation applications. They comprise different functional inorganic components such as titania, vanadia, tin oxide, or lithium manganese phosphate. Our results demonstrate that bioinspired structural design provides access to mechanically stable ceramic based materials whose other functional properties are well maintained or even improved. This renders such materials especially attractive for applications that require a long-term mechanical stability.
11 June 2018, 16:00 h. Salón de Actos
Omar M. Yaghi
Department of Chemistry, University of California, Berkeley, California, USA
Linking molecular building units by strong bonds to make crystalline extended structures (Reticular Chemistry) has given rise to metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), thus bringing the precision and versatility of covalent chemistry beyond the atoms and molecules. The key advance in this regard has been the development of strategies to overcome the “crystallization problem”, and the use of metal-oxide clusters as secondary building units to impart unprecedented structural robustness, high surface area, and permanent porosity. To date, thousands of MOFs and COFs are made as crystalline materials. The molecular units thus reticulated become part of a new environment where they have (a) lower degrees of freedom because they are fixed into position within the framework; (b) well-defined spatial arrangements where their properties are influenced by the intricacies of the pores; and (c) ordered patterns onto which functional groups can be covalently attached to produce chemical complexity. The notion of covalent chemistry beyond molecules is further strengthened by the fact that covalent reactions can be carried out on such frameworks, with full retention of their crystallinity and porosity. MOFs are exemplars of how this chemistry has led to porosity with designed metrics and functionality, chemically-rich sequences of information within their frameworks, and well-defined mesoscopic constructs in which nanoMOFs enclose inorganic nanocrystals and give them new levels of spatial definition, stability, and functionality. The advent of COFs extends the field of organic chemistry beyond discrete molecules (0D) and polymers (1D) into “infinite” two and three dimensions. Molecular weaving, the mutual interlacing of long threads at the molecular level, was first accomplished in COF to make the true woven material. This discovery combines the porosity and robustness of frameworks with mechanically deformable and stretchable capability.