Abstract (eng)
Polymeric, stimuli-responsive materials are one of the central research topics in modern soft mater physics. This thesis is a study of polymer-like structures with magnetic nanoparticles as monomers, systems that emerged in attempts to capitalize on the potential of magneto-responsive materials, commonly referred to as magnetic filaments. Using magnetic fields as a stimulus is interesting because of the dynamic intensity control and/or great spatial resolution that can be achieved with them, in addition to the fact that they typically do not interfere with biological tissues and processes. Using Molecular dynamics simulations as the principal tool of investigation, we encompass key elements of magnetic filament design: microstructure, crosslinking, magnetic nature and shape of monomers, and systematically relate them to the properties of a single filament at equilibrium and its rheological response to shear flow. Furthermore, we explore the effects of van der Waals and electrostatic forces in terms of a central attraction between the monomers of a filament, and using the Lattice-Boltzmann method, encompass hydrodynamic effects on the rheology of magnetic filaments. A magnetic filament, as a representative member of highly magneto-responsive, smart nanomaterials, is a compelling system only as far as it has a flexible backbone and a highly tunable microstructure. Flexible, nanoscopic magnetic filaments, with a finely tunable microstructure, have not been synthesized yet. The key difficulty in such an endeavor is instilling selective, anisotropic interactions between nanoobjects that are otherwise entirely isotropic, with colloids that are chemically stable and when crosslinked, remain so permanently. To this end, we present a theoretical investigation of magnetic filaments based on DNA nanochambers, nanoobjects that have been used to synthesize nanopolymers. We analyze their mechanical response to compression and study the rheology of magnetic filaments based on DNA nanochambers, subjected to the simultaneous action of shear flow and a stationary external magnetic field perpendicular to the flow. We demonstrate that DNA nanochambers represent a compelling, finely tunable platform for creating highly magneto-responsive, nanoscopic, polymer-like structures.