Inter- and intramolecular nanomechanical interactions of homo- and heterogenous polymers

各种材料的宏观力学性能，特别是聚合物的宏观力学性能，是由基于聚合物构型和构象、链长以及它们之间相互作用的纳米力学异质性决定的。在这个项目中，将详细研究个人对相关聚合物体系纳米力学性能的贡献作为模型。为此，将开发一种多频原子力显微镜方法，该方法可以在三个空间方向上定量地捕捉表面和正下方的纳米力学性质。利用弯曲悬臂振动的第一本征模，可以控制针尖在样品表面的压痕深度，同时在调幅模式下跟踪表面形貌。通过对第二弯曲本征模和第一扭转本征模的附加激励和调频检测，可以分析针尖-样品相互作用在两个空间方向上的保守和耗散部分。研究了聚苯乙烯和聚丁二烯薄膜样品的链长和薄膜厚度对纳米力学性能的影响，从而对分子间相互作用的影响。这些性质与相同组成的交联型和双嵌段/三嵌段(co-co)聚合物的性质的比较提供了关于纳米尺度上分子内相互作用的有价值的信息。此外，样品表面的逐步侵蚀和随后通过纳米层析成像对三块样品的体积重建允许解开关于纳米机械性能的结构-性能关系。紫外光辐射对聚合物的影响将通过拉曼光谱和纳米机械分析来研究。由此，可以建立嵌段共聚物的化学转变和机械改变之间的关系。

The macroscopic mechanical properties of a variety materials, in particular that of polymers, are determined by their nanomechanical heterogeneity based on the polymer configuration and conformation, chain length and interactions among them. The individual contributions to the nanomechanical properties of a relevant polymer system as model is to be studied in detail in this project. To this end, a multifrequency atomic force microscopy method will be developed that can capture quantitatively the nanomechanical properties at the surface and directly beneath in three spatial directions. Using the first eigenmode of the flexural cantilever vibration the indentation depth of the tip into the sample surface can be controlled while the topography is tracked in the amplitude modulation mode. Through the additional excitation and frequency modulated detection of the second flexural and the first torsional eigenmodes, the conservative and dissipative portions of the tip-sample interaction in two spatial directions can be analyzed. The influence of the chain length and film thickness of thin polystyrene and polybutadiene samples on the nanomechanical properties and thus, on the intermolecular interactions is to be investigated. The comparison of these properties with that of cross-linked and diblock/triblock (co-)polymers of the same components provides valuable information about the intramolecular interactions on the nanoscale. Additionally, the stepwise erosion of the sample surface and the subsequent volume reconstruction of the triblock samples by nanotomography allows for unravelling the structure-property relationship with respect to the nanomechanical properties. Implications of UV radiation on the polymers will be studied by Raman spectroscopy and nanomechanical analysis. Thereby, a relationship between the chemical transformation and mechanical alteration of the block copolymers can be established.