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

• Applicants: Professor Dr. Marcus Müller; Professor Dr. Manfred Wilhelm
• Subject Area: Experimental and Theoretical Physics of Polymers ; Polymer Materials
• Term: since 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263005595

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.

• DFG Programme: Research Grants
• Co-Investigator: Dr. Nico Dingenouts