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的有价值的模型系统，但在传感或作为微机械构建块(开关、阀门等)等应用方面也具有潜在的兴趣-尤其是聚电解质多层膜(PEM)在这方面很有前途，因为它们的厚度可以在纳米级生产和精确调整，并且它们的组成可以在分子水平上进行控制。众所周知，质子交换膜可以具有非常不同的机械性能，这取决于它们的分子结构(组成、分子内相互作用)。然而，到目前为止，对这些结构和性质之间的关系还缺乏定量的了解。在拟议的项目中，我们希望建立独立的多层膜，这些多层膜的结构，特别是它们(离子和/或共价)的交联密度和层形成分子之间的疏水相互作用是明确的，并研究它们的机械性能。为此，将采用一种综合的方法，将用于层积的新型定制聚电解质的合成与新的独立式聚电解质膜的机械表征技术的开发相结合。这不仅揭示了质子交换膜的静态力学性能，而且为理解和调整这些材料对环境变化的响应能力提供了基础，例如pH和盐浓度的变化。

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.