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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 21: Poster II

CPP 21.33: Poster

Dienstag, 19. März 2024, 18:00–20:00, Poster E

Orientation of dynamically asymmetric diblock copolymers in shear flow — •Niklas Blagojevic and Marcus Müller — Institut für Theoretische Physik, Universität Göttingen

The ability of diblock copolymers to assemble into periodic structures with length scales in the nanometer range offers many applications. For practical applications, it is often desirable that the microstructures have a high degree of order even on large length scales and are oriented in a desired direction. It is possible to order and orient the microstructures by shearing the copolymer melt. However, the details of the orientation mechanism under shear are not fully understood. In experiments, different orientations are found depending on copolymer type and shear amplitude. Lamellae-forming copolymers were in some cases oriented parallel to the shear gradient and in other cases perpendicular. In our simulations, we analyse the effect of a dynamical asymmetry, where one block has slower time scales than the other. We can show that the parallel orientation is preferred for high dynamic asymmetries while the perpendicular is preferred for small asymmetries. To investigate this, we conducted molecular dynamics simulations of a highly coarse-grained polymer melt using dissipative-particle dynamics under shear flow. We controlled the dynamic asymmetry via a friction parameter as well as via so-called slip-springs, which represent entanglements of the polymers. Different settings were used to determine the stable orientation, for example the simulation of a system with differently oriented lamellae under shear or the simulation of a quench from a disordered state under shear.

Keywords: copolymers; diblock; molecular dynamics; rheology