Magnetically functionalized star polymers and polymer melts in MPCD simulations

Abstract

Star polymers are macromolecules which consist of a central core, to which a number of linear polymer chains are attached. In this work, the free ends of those polymer chains are decorated, or functionalized, with super-paramagnetic particles, the magnetic dipole moments of which are aligned with an external magnetic field. In computer simulations, the resulting molecule is subjected to shear flows of varying strength, and the conformational properties, such as size and shape, as well as dynamic properties in the form of whole-body rotations, are studied as functions of the shear rate and the relative orientation of the shear flow direction with regard to the axis of the external magnetic field. When these properties are compared to corresponding ones in the case of non-magnetic star polymers, one finds that some phenomena are largely unaffected by the introduction of magnetic moments, while others emerge, or behave qualitatively differently, due to the spontaneous self-assembly of columns of magnetic particles. Further, this thesis contains new and improved results pertaining to the viscoelastic behavior of polymer melts, partly building on research carried out in the course of the author's Diplomarbeit (master's thesis). In both topics, a hybrid simulation method of Multi-Particle Collision Dynamics (MPCD) and Molecular Dynamics (MD) is employed, using a simulation and data analysis package developed and published by the thesis author; a short description of said package is provided in this text.