Experimental investigation and numerical simulation of the orientation processes in block copolymers on a macroscopic and a molecular level

本项目继续的综合目标是更好地了解动态不对称性和复杂的分子拓扑对均聚物和嵌段共聚物熔体的线性和非线性流变性的影响。这一目标进一步分为四个工作包：1)明确嵌段共聚熔体中聚合物链段的动态不对称性是否对聚合物片层取向的稳定性有一定的影响。对于相同的迁移率，就像在计算机模拟或第一个应用的聚合物体系中的情况一样，垂直取向被发现是稳定的。然而，对于许多实验系统来说，观察到的是平行系统。应在实验和模拟中增加迁移率的差异，以评估其对片层取向稳定性的影响。2)另一个需要回答的问题是，层状两嵌段共聚物和层状三嵌段共聚物在剪切过程中的片层取向动力学是否存在差异。需要澄清的是，三嵌段共聚物固定在一个薄层上，还是通过固定在两个不同的薄层上架桥，对所观察体系的取向动力学有显著的影响。3)研究纠缠对非线性流变学和高次谐波的影响。首先，应研究不太复杂的体系，如均聚物熔体。为了评估分子量和缠结的数量的影响，我计划通过模拟高聚物链的纠缠的滑移弹簧的模拟和没有滑移弹簧的模拟来研究模拟中的非线性行为。4)拟对聚合物拓扑结构的影响进行研究。随着侧链数目的增加，缠结对聚合物动力学的影响减小。在模拟和实验中，侧链数目逐渐增加，并研究了聚合物熔体的非线性行为。用这种方法可以弄清楚高次谐波是由纠缠产生的，还是来自复杂的弛豫谱。

The comprehensive goal of the continuation of this project is a better understanding of the influences like dynamic asymmetries and complex molecular topologies on the linear and nonlinear rheological properties of homopolymer and block copolymer melts. This goal is further divided into four working packages1) It shall be clarified if a dynamic asymmetry of the polymer blocks in block copolymer melts has some influence on the stability of the orientation of polymer lamellae. For identical mobilities, as it is the case in computer simulations or the polymer systems of the first application, the perpendicular orientation is found to be the stable one. However, for many experimental systems the parallel one is observed. The difference in mobility shall be increased in the experiment and in the simulations to evaluate its influence on the stability of the lamellae’s orientation. 2) Another question to answer is if there are differences in the orientation kinetics of lamellae in shear between lamellar diblock copolymers and lamellar triblock copolymers. It shall be clarified if the fixation of triblock copolymers in one lamella or the bridging by a fixation in two different lamellae shows a noticeable influence on the orientation kinetics of the observed system. 3) The influence of entanglements on the nonlinear rheology and on higher harmonics shall be investigated. First, less complex systems as homopolymer melts shall be investigated. In order to evaluate the influence of molecular weight and thus the amount of entanglements, the nonlinear behavior in simulations I planned to be investigated by simulations with slip-springs, which mimic entanglements of polymer chains, and simulations without these. 4) The influence of polymer topology is planned to be investigated. With an increasing number of sidechains the influence of entanglements on the dynamics of the polymer decreases. The number of sidechains is gradually increased in the simulations and in the experiments and the nonlinear behavior of the polymers’ melt is investigated. With this approach it is possible to clarify if higher harmonics result from entanglements or from a complex relaxation spectrum.