Structure - mechanical property relations of polyelectrolyte multilayer and free-standing membranes

具有纳米级厚度和明确机械性能的独立膜是基础研究中有价值的模型系统，但在传感或微机械构建模块（开关、阀门等）等应用中也有潜在的兴趣。特别是聚电解质多层膜（PEMs）在这方面很有前途，因为它们的厚度可以在纳米橙中产生和精确调节，它们的组成可以在分子水平上控制。众所周知，PEMs根据其分子尺度结构（组成、分子内相互作用）的不同，具有截然不同的机械性能。然而，到目前为止，对这些结构性质关系的定量理解仍然缺失。在提议的项目中，我们想要建立独立的多层材料，它们的结构很好，特别是它们的（离子和/或共价）交联密度和层形成分子之间的疏水相互作用，并研究它们的机械性能。为此，将采用一种综合的方法，将合成新颖的、量身定制的聚电解质用于层的形成，与开发新的独立聚电解质膜的机械表征技术相结合。这不仅可以阐明PEMs的静态力学性能，还可以为理解和调整这些材料对环境变化（如pH值和盐浓度）的响应性提供基础。

Freestanding membranes with thicknesses on the nanoscale and well defined mechanical properties are valuable model systems for fundamental studies, but are also potentially interesting for applications like sensing or as micromechanical building blocks (switches, valves,...) - In particular polyelectrolyte multilayer membranes (PEMs) are promising in this respect because their thickness can be produced and precisely adjusted in the nanorange, and their compositon can be controlled on the molecular level. It is well known that PEMs can have strongly differing mechanical properties, depending on their molecular scale structure (composition, intramolecular interactions). However a quantitative understanding of these structure property relations is missing so far. In the proposed project, we want to build up freestanding multilayers which are well defined in their structure, in particular in their (ionic and/or covalent) crosslinking densities and hydrophobic interactions between the layer forming molecules and study their mechanical properties. To do so, a comprehensive approach will be made, combining the synthesis of novel, tailored polyelectrolytes for layer buildup with the development of mechanical characterization techniques for the new freestanding polyelectrolyte membranes. This will not only shed light on the static mechanical properties of PEMs, but also provide the basis for understanding and tailoring the responsiveness of these materials towards environmental changes such as of pH and of salt concentration.