Correlation of molecular dynamic and mechanical properties in the linear and non-linear regime of comb-like homopolymers via FT-rheology and multi-quantum-NMR-spectroscopy

本应用项目涵盖了已定义的支链模型聚合物的分子动力学研究。目的是为了更好地理解支链结构及其非线性流变特性之间的基本联系。因此，确定的支状梳状聚合物将通过活阴离子聚合合成。一方面，制备部分氘化（仅主链或侧链）的梳状结构用于多量子核磁共振光谱和流变学，另一方面，制备完全质子化的梳状结构仅用于流变学测量。梳状聚合物的形成可以通过硅氢化或环氧化对骨架进行功能化来实现。然后，活侧链可以通过所谓的接枝方法连接到引入的官能团上。聚合体氘化部分所需的单体异戊二烯-d8和丁二烯-d6既可以自行合成，也可以在市场上购买。流变学表征将集中于借助ft流变学在非线性状态下的测量。这些实验将调查结构和非线性之间的关系，以及检测不同的松弛时间。此外，还将首次对非线性振动剪切实验中的法向力进行研究。由于部分氘化的梳状结构，多量子核磁共振实验将使我们能够独立地检测主链和侧链的不同弛豫过程和相关的弛豫时间。然后可以将结果与流变学测量得到的松弛时间进行比较。因此，这将有可能在分子水平上更好地理解机械松弛过程，并区分主链和侧链的贡献。此外，在主干内改变氘化块的位置将使研究梳状结构的弛豫模式层次成为可能。使用定制的流变核磁共振装置，可以在振荡剪切实验期间同时进行核磁弛豫研究。通过这种设置，可以研究核磁共振光谱和流变学之间在时间和长度尺度上的动态效应。在拟议的项目之外，进一步的合作将涉及松弛时间的模拟，从而将有助于提高对非线性制度过程的基本理解。

This applied project covers the study of molecular dynamics of defined, branched model polymers. The aim is to make a contribution towards a better understanding the basic connection between branched structures and their non-linear rheological properties. Therefore, defined branched, comb-like polymers will be synthesized via living anionic polymerization. On the one hand, partly deuterated (only backbone or only sidechains) comb structures will be prepared for multi-quantum-NMR-spectroscopy and rheology, on the other hand, fully protonated comb structures will be prepared solely for rheological measurements. The formation of comb polymers can be achieved by functionalization of the backbone via hydrosilylation or epoxidation. Afterwards, the living sidechains can be attached to the introduced functional groups by the so called grafting-onto method. The monomers isoprene-d8 and butadiene-d6, which are needed for the deuterated parts of the polymers, can either be self synthesized or can be commercially purchased.The rheological characterization will concentrate on measurements in the non-linear regime with the aid of FT-rheology. These experiments will survey the correlation between structure and nonlinearity, as well detect various relaxation times. Moreover, for the first time, the normal forces during an oscillation shear experiment in the non-linear regime will be examined. Due to the partly deuterated comb structures, multi-quantum-NMR-experiments will allow us to detect the different relaxation processes and the associated relaxation times of the backbone and the sidechains independently of each other. The results can then be compared with relaxation times obtained from rheological measurements. Thus, it will be possible to better understand the mechanical relaxation processes on a molecular level and separate the contribution of backbone and sidechains. Furthermore, varying positions of a deuterated block within the backbone will enable the study of the hierarchy of relaxation modes for a comb structure. With a custom-made rheo-NMR device, nuclear magnet relaxation studies can be simultaneously performed during an oscillatory shear experiment. With this setup, dynamic effects that lie on a time and length scale between NMR-spectroscopy and rheology can be studied.Beyond the proposed project, further cooperations will involve the simulation of relaxation times and thus will help to improve the basic understanding of the processes in the non-linear regime.