Mobility of Single Molecules at the Interfaces of Thin Polymer Films

纳米技术和聚合物的结合是自然科学和工程学中一个非常令人兴奋的跨学科研究领域。在这里，创建的接口的流程和结构与以前从Bulk中了解的有很大不同。通过这个项目中直接单分子观测的更深层次的可能性，我们期待对这种界面上的动力学有新的见解，从中可以产生有助于解决我们现代世界挑战的创新。特别是，对于聚合物材料的纳米技术应用来说，对迁移率的详细了解是至关重要的，因为随着微型化程度的提高，界面日益主导着材料的性能。界面上的动态对电子元件、有机发光二极管、太阳能电池或选择性分离系统和膜等具有极大的相关性，并决定了它们的长期稳定性。尽管进行了广泛的研究，但对界面处聚合物动力学和聚合物性质的变化仍未完全了解。其中一个原因是不同的方法对聚合物不同区域的行为进行了不同的平均。为了避免这一点，必须在单分子水平上观察聚合物的动力学。在这个项目中，我们关注聚合物薄膜中靠近界面(空气或衬底)的分子的迁移率。利用现代单分子荧光方法，我们观察到单探针分子在聚合物界面的平移和旋转运动。与以前的研究相比，我们现在可以在实验上达到所需的空间纳米分辨率，特别是垂直于界面的分辨率。这种轴向分辨率可以通过最近发展起来的金属诱导能量转移(MIET)成像来实现，我们将在该项目中将其与单分子定位显微镜和散焦广场显微镜相结合，使用一种新型的单分子灵敏的广场荧光寿命探测器。因此，单分子的平移和转动运动可以与它们的位置相关联，具有前所未有的各向同性的3D分辨率。因此，我们将研究荧光探针在聚合物薄膜界面上平移和旋转运动的温度依赖性，并阐明不同聚合物界面上的迁移率是否以及随着哪种z轮廓的变化。因此，我们的项目代表了从系综测量到局部动力学观察的重要一步，并将决定性地扩展对纳米范围内界面附近的(宏观)分子迁移率的理解。

Combining nanotechnology and polymers is an extremely exciting, interdisciplinary field of research in the natural sciences and engineering. Here, interfaces are created at which processes and structures differ significantly from what was previously known from bulk. Through deeper possibilities of direct single-molecule observation in this project, we expect new insights into the dynamics at such interfaces, from which innovations that contribute to solutions to the challenges of our modern world can arise. In particular, a detailed understanding of mobility is essential for nanotechnological applications of polymeric materials, as interfaces increasingly dominate the properties of materials with increasing miniaturization. The dynamics at interfaces is of utmost relevance for electronic components, organic light-emitting diodes, solar cells or selective separation systems and membranes, among others, and also determines their long-term stability. Despite extensive research, the changes in polymer dynamics and polymer properties at interfaces are still not fully understood. One of the reasons for this is the different averaging of individual methods over the behavior of different areas of the polymer. To circumvent this, the observation of polymer dynamics at the single molecule level is necessarily required. In this project, we focus on the mobility of molecules in polymer films near an interface (air or substrate). Using modern single-molecule fluorescence methods, we observe the translational and rotational motion of single probe molecules at polymer interfaces. In contrast to earlier studies, we can now experimentally achieve the required spatial nanometer resolution, especially perpendicular to the interface. This axial resolution can be achieved by recently developed metal-induced energy transfer (MIET) imaging, which we will combine with single-molecule localization microscopy and defocused wide-field microscopy in the project using a novel, single-molecule sensitive wide-field fluorescence lifetime detector. Thus, translational and rotational motion of single molecules can be correlated with their position with unprecedented isotropic 3D resolution. Thus, we will investigate the temperature dependence of the translational and rotational motion of fluorescent probes at the interfaces of polymer films and elucidate whether and with which z-profile the mobility changes at different polymer interfaces.Our project thus represents an essential step in the transition from ensemble measurements, which average over the entire dynamics in a film, to the observation of local dynamics and will decisively expand the understanding of the mobility of (macro)molecules in the vicinity of interfaces in the nanometer range.