Regensburg 2016 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: Focus: Functional Polymer Hybrids I

CPP 20.8: Vortrag

Dienstag, 8. März 2016, 12:00–12:15, H51

Mesoscopic modeling of magnetic gels: reversibly switching elastic and superelastic stress-strain properties — Peet Cremer, Giorgio Pessot, Hartmut Löwen, and •Andreas M. Menzel — Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany

Magnetic gels are generated by embedding magnetic colloidal particles into a permanently crosslinked, possibly swollen elastic polymer matrix. Several of their material properties can be reversibly switched from outside by applying external magnetic fields during operation. We model the switchability of such material properties on the mesoscopic level.

Previously, we had introduced simplified dipole-spring approaches to study the reversible tunability of linear elastic and dynamic properties. In contrast to that, we here mainly report on switchable nonlinear stress-strain properties. For this purpose, we focus on anisotropic magnetic gels that contain chain-like aggregates of magnetic colloidal particles. Continuum elasticity theory is now used to describe the elastic behavior of the surrounding polymer matrix. Upon stretching along the chain direction, we predict a pronounced plateau-like ("superelastic") regime on the stress-strain curves. Remarkably, applying external magnetic fields, this plateau can be shifted along the stress-strain curves or even be switched off. We identify two underlying mechanisms: a detachment of the embedded chain-like aggregates and a flipping of the magnetic moments. The origin of both mechanisms is explained. It should be possible to observe these effects on real experimental samples and to exploit them, e.g., for the construction of soft actuators.