Superparamagnetic nanoparticles with LC polymer brush shell as efficient dopants for ferronematic phases. Issue 43 (26th August 2021)

• Record Type: Journal Article
• Authors: Koch, Karin; Kundt, Matthias; Barkane, Anda; Nadasi, Hajnalka; Webers, Samira; Landers, Joachim; Wende, Heiko; Eremin, Alexey; Schmidt, Annette M.
• Is Part Of: Physical chemistry chemical physics. Volume 23:Issue 43(2021)
• Page Start: 24557
• Page End: 24569
• Publication Date: 2021-08-26
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d1cp03005a
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : A promising route for the fabrication of ferronematic phases is the attachment of a LC polymer shell onto the surface of nanoparticles. Here, we extend this approach to ferronematic phases based on superparamagnetic particles in a 5CB matrix. Abstract : Liquid crystal (LC) based magnetic materials consisting of LC hosts doped with functional magnetic nanoparticles enable optical switching of the mesogens at moderate magnetic field strengths and thereby open the pathway for the design of novel smart devices. A promising route for the fabrication of stable ferronematic phases is the attachment of a covalently bound LC polymer shell onto the surface of nanoparticles. With this approach, ferronematic phases based on magnetically blocked particles and the commercial LC 4-cyano-4′-pentylbiphenyl (5CB) liquid crystal were shown to have a sufficient magnetic sensitivity, but the mechanism of the magneto–nematic coupling is unidentified. To get deeper insight into the coupling modes present in these systems, we prepared ferronematic materials based on superparamagnetic particles, which respond to external fields with internal magnetic realignment instead of mechanical rotation. This aims at clarifying whether the hard coupling of the magnetization to the particle's orientation (magnetic blocking) is a necessary component of the magnetization–nematic director coupling mechanism. We herein report the fabrication of a ferronematic phase consisting of surface-functionalized superparamagnetic Fe3 O4 particles and 5CB. We characterize the phase behavior and investigate the magneto-optical properties of the new ferronematic phase and compare it to the ferronematic system containing magnetically blocked CoFe2 O4 particles to get information about the origin of the magneto–nematic coupling.