Understanding and controlling the lateral hydrogel shell deformation of core/shell microgels at air/waterinterfaces for smart surface nanopatterning

该项目的目标是调查和澄清自由漂浮的核/壳微凝胶胶体单分子层在空气/水界面的横向延伸。此外，单层延伸将被用作智能纳米涂层技术，用于制备相互作用的等离子表面涂层。这些工作的基础将是具有硬核的微凝胶和柔软、可变形的水凝胶壳。与纯聚合物微凝胶不同，这些颗粒自发形成高度有序、自由浮动的单分子层。在之前的一项概念验证研究中，我们可以证明单层在几分钟到几小时的时间尺度上横向扩展。这种延伸的确切来源、其动力学和影响延伸行为的结构参数目前尚不清楚。我们只能表明，拉伸发生得非常缓慢，并且拉伸过程中单分子层的有序度几乎不受影响。基于这一认识，我们想要研究不同结构参数和外部参数对伸展动力学的影响。为此，我们将合成不同柔软度、不同交联剂分布和不同电荷的核壳微凝胶。这些材料将根据其膨胀能力和表面活性进行表征。一项中心任务将是确定界面覆盖区域和未覆盖区域之间的表面压力差。我们将利用自由漂浮的单分子膜在不同停留时间后转移到玻璃基板上，通过不同的显微技术来研究微结构的时间演化。通过改变界面上单层面积的大小和通过表面活性剂降低表面张力，我们将确定如何通过外部参数来控制延伸动力学。此外，通过使用染料标记的核心，我们第一次有可能在光谱学上跟踪单层延伸。与此相反，使用具有不同大小的等离子体金核心的微凝胶的实验将允许澄清等离子体共振耦合现象。在这里，我们还将使用原位光谱对自由浮动的单分子膜进行随时间变化的实验。我们将利用掠入射小角X射线散射(GISAXS)原位研究薄膜的微观结构。由此，我们可以推导出单层结构与光学耦合过程之间的潜在关联，例如局域表面等离子体共振与超晶格的衍射模之间的关联。实验结果将得到光学性质的理论计算的支持。该项目的成果一方面将有助于对界面软系统的基本了解，另一方面将有助于开发用于制备光学活性胶体涂层的智能纳米涂层程序。

The objectives of this project are the investigation and clarification of the lateral extension of freely floating colloidal monolayers of core/shell microgels at air/water interfaces. Furthermore, the monolayer extension will be used as a smart nanopatterning technique for the preparation of interacting, plasmonic surface coatings.The basis for these works will be microgels with hard cores and soft, deformable hydrogel shells. In contrast to purely polymeric microgels, these particles form highly ordered, freely floating monolayers spontaneously. In a previous proof-of-concept study we could show that the monolayers expand laterally on timescales of minutes to hours. The exact origin of this extension, its kinetics and the structural parameters influencing the extension behavior are currently unknown. We could merely show that the extension occurs very slowly and that the degree of order of the monolayer during extension remains nearly unaffected. Based on this knowledge we want to study the kinetics of extension in dependence of different structural and external parameters. For this, we will synthesize core/shell microgels of different softness, cross-linker distribution and charge. These will be characterized with respect to their swelling capacity and surface activity. A central task will be the determination of the difference in surface pressure between covered and uncovered areas of the interface. We will use the transfer of the freely floating monolayers onto glass substrates after different dwell times to study the temporal evolution of the microstructure by different microscopy techniques. By varying the size of the monolayer area at the interface and the reduction of the surface tension through a surfactant, we will identify how the extension kinetics can be controlled by external parameters. Furthermore, for the first time it becomes possible for us to follow the monolayer extension spectroscopically in-situ by the use of dye-labeled cores. In contrast to this, experiments with microgels featuring plasmonic gold cores of various sizes will allow to clarify plasmon resonance coupling phenomena. Here we will also use in-situ spectroscopy for time dependent experiments on freely floating monolayers. We will investigate the microstructure in-situ by grazing-incidence small-angle X-ray scattering (GISAXS). With this we can derive potential correlations between monolayer structure and optical coupling processes, e.g. between localized surface plasmon resonances and diffraction modes of the superlattice. The experimental findings will be supported by theoretical calculations of the optical properties. The results of this project will contribute on the one hand to the fundamental understanding of soft systems at interfaces and on the other hand to the development of smart nanopatterning procedures for the preparation of optically active, colloidal coatings.