Innovative synthesis routes towards hierarchically organized nanostructured materials combined with in-situ SAXS characterization techniques

为了更好地理解纳米结构材料的形成过程，我们将通过原位小角X射线散射在纳米和微米尺度上研究溶胶-凝胶系统中的相分离现象。高度多孔的氧化物，例如二氧化硅、二氧化钛、氧化铝等，或通过应用金属二醇盐的新合成路线制备的混合二氧化硅-金属氧化物材料，并包含具有不同孔径等级的多孔网络，将用作模型系统。设想不仅将氧化物材料的范围从二氧化硅扩展到其它过渡金属氧化物，而且例如通过溶胶的机械剪切将一定程度的各向异性引入孔域。因此，拟议的研究包括化学和物理学的三个相互关联的元素：1。通过定制的前体分子进行精心的网络设计; 2.）创新的制造方法和3.）详细的表征网络的发展emphazising在原位（小角度）X射线散射和衍射。从化学的角度来看，我们将开发新的合成路线走向高度多孔，分层组织的过渡金属氧化物单块应用金属diolates。金属二醇盐具有可在纯水溶液中加工的优点，因此与在合成中用作结构导向剂的溶致液晶相相容。作为起始化合物，相应的醇盐，例如对于二氧化钛，四异丙氧基钛将被乙二醇化以得到作为稳定且酸溶性前体的钛酸双（2-羟乙基）酯。该前体将在预先形成的水性溶致液晶相的存在下加工，以产生具有故意设计的孔结构的氧化物。我们将证明这种合成方法对材料的高潜力与多峰孔径分布的应用类似的（混合）金属前体。从物理的角度来看，一个焦点在于从乙二醇化前体分子获得的最终材料的结构研究。此外，先前的实验已经表明，与预期相反，溶致液晶相不是直接模板化的，而是在添加乙二醇化前体时发生重组过程。最终的网络结构受形成机制的强烈影响。因此，第二个重点是原位SAXS测量，在混合物中从溶胶到最终凝胶的结构演变，以允许更深入地了解潜在的相分离过程。由于外部参数如搅拌速度、离心、温度等对孔结构有很大影响，因此计划进行额外的测量，包括孔系统的剪切诱导排列和不同外部实验参数下的测量。

Aiming at a better understanding of the formation process of nanostructured materials, we will investigate phase separation phenomena in sol-gel systems on the nano- and micrometer length scale via in-situ small angle X-ray scattering. Highly porous oxides, for example silica, titania, alumina, etc. or mixed silica-metal oxide materials prepared via a novel synthesis route applying metal diolates and comprising a porous network with different levels of hierarchy in the pore sizes will serve as model systems. It is envisioned not only to expand the range of oxidic materials from silica to other transition metal oxides, but also to induce a certain degree of anisotropy into the pore domains, e.g. by mechanical shearing of the sol. Thus, the proposed research comprises three inter-related elements from chemistry and physics: 1.) deliberate network design by tailor-made precursor molecules; 2.) innovative fabrication methods and 3.) detailed characterization of the network development emphazising on in-situ (small angle) X-ray scattering and diffraction. From a chemical point of view, we will develop novel synthetic routes towards highly porous, hierarchically organized transition metal oxide monoliths by applying metal diolates. Metal diolates have the advantage of being processable in purely aqueous solution and thus being compatible with lyotropic liquid crystal phases that will serve as structure-directing agents in the synthesis. As starting compounds the respective alkoxides, e.g. for titania, titanium tetraisopropoxide will be glycolated to give bis(2-hydroxyethyl)titanate as a stable and acid-soluble precursor. This precursor will be processed in the presence of a preformed aqueous lyotropic liquid crystalline phase to yield the oxide with a deliberately designed pore structure. We will demonstrate the high potential of this synthetic approach towards materials with a multimodal pore size distribution by the application of analogous (mixed) metal precursors. From a physical point of view, one focus lies on the structural investigation of the final materials obtained from the glycolated precursor molecules. In addition, previous experiments have shown that contrary to what was expected the lyotropic liquid crystalline phase is not directly templated, but that reorganisation processes occur upon addition of the glycolated precursor. The final network structure is strongly influenced by the mechanism of formation. Therefore, the second focus is on in-situ SAXS measurements, following the structural evolution in the mixture from the sol to the final gel to allow for a deeper understanding of the underlying phase separation processes. Since external parameters such as stirring speed, centrifugation, temperature, etc. have a strong influence on the pore structure, additional measurements are planned comprising shear-induced alignment of the pore system and measurements under different external experimental parameters.