R. Stannarius: Magneto-optical switchable anistropic pigment suspensions
Description
The principal goal is the combination of two successful concepts of soft matter physics, magnetic fluids and liquid crystals, in order to develop a new class of materials for magneto-optical switching and magneto-mechanical effects. Suspensions of magnetic particles have already found manifold applications, liquid crystals (LC), on the other hand, combine fluidity with spontaneous order and anisotropy. Attempts to produce stable ferronematic suspensions with molecular LC had, for several reasons, only little success so far.
We use an alternative approach and start with suspensions of anisotropic crystallites, which can form nematic phases [1]. Ferromagnetic particles are dispersed in these suspensions. We expect that sterical interactions of the crystallites with anisometric ferroparticles are considerably more effective than interactions with molecular nematics.
Preliminary work of our collaborator (Yurii Reznikow) on ferromagnetic filled carbon nanotubes in classical nematics [2] demonstrated a ’command’-effect, by which these suspensions can be controlled magnetically [3,4]. Optical and mechanical properties can be controlled already with weak magnetic fields. Vice versa, the magnetic properties of our suspensions shall be sensitive for a control by light or by electric fields. We expect that the doped mixtures will switch magneto-optically, and that they show magnetically induced birefringence and dichroism already at field strengths of few mT.
Polarisation microscope image of a nematic suspension (approx. 200 nm long pigment crystallites in an apolar solvent) with flow-induced textures of the director field around air inclusions.
Project Manager
Prof. Dr. Ralf Stannarius, Otto-von-Guericke-Universität Magdeburg
Staff
PD Dr. Alexey Eremin, Otto-von-Guericke-Universität Magdeburg
DP Kathrin May, Otto-von-Guericke-Universität Magdeburg
Grant period
2013 -
Publications
[1] A. Eremin et al., Adv. Funct. Mater. 21 402 (2011)
[2] K. May et al. Electric-Field-Induced Phase Separation and Homogenization Dynamics in Colloidal Suspensions of Dichroic Rod-Shaped Pigment Particles. Langmuir 30 7070 (2014)
[3] K. May et al. Piezoelectric fiber mats containing polar rodshaped pigment particles. RSC Advances 4 44223 (2015)
[4] A. Eremin, R. Stannarius, Y. Geng, T. Ostapenko, P. K. Challa, J. T. Gleeson, A. Jakli, and S. Klein. Peculiarities of the magneto-optical response in dispersions of anisometric pigment nanoparticles. RSC Advances, 6 80666, (2016)
[5] Ingo Appel, Hajnalka Nadasi, Christian Reitz, Nerea Sebastiaan, Horst Hahn, Alexey Eremin, Ralf Stannarius, and Silke S. Behrens. Doping of nematic cyanobiphenyl liquid crystals with mesogenhybridized magnetic nanoparticles. Phys. Chem. Chem. Phys., in press, (2017)
[6] K. May, A. Eremin, R. Stannarius, B. Szabo, T. Börzsönyi, I. Appel, S. Behrens, and S. Klein. Exceptionally large magneto-optical response in dispersions of plate-like nanocrystallites and magnetic nanoparticles. J. Magn. Magn. Materials, 431 79, (2017).
[7] A. M. Storozhenko, R. Stannarius, A. O. Tantsyura, and I. A. Shabanova. Measurement of the torque on diluted ferrofluid samples in rotating magnetic elds. J. Magn. Magn. Materials, 431 66, (2017).
[8] K. May, A. Eremin, R. Stannarius, S. Peroukidis, S. Klapp, and S. Klein. Colloidal suspensions of rodlike nanocrystals and magnetic spheres under external magnetic stimulus: Experiment and molecular dynamics simulation. Langmuir, 32 5085, (2016)
Contact
Otto-von-Guericke-Universität Magdeburg
Universitätsplatz 2
Gebäude 16
39106 Magdeburg