Ferronematic Co(II) Complex: An Active Filler for Magnetically Actuated Soft Materials

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 20; no. 15; pp. e2307006 - n/a
• Main Authors: Damoc, Madalin, Tiron, Vasile, Tugui, Codrin, Varganici, Cristian‐Dragos, Stoica, Alexandru‐Constantin, Novitchi, Ghenadie, Dascalu, Mihaela, Cazacu, Maria
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.04.2024
• Subjects: Anisotropy; cobalt; Cobalt compounds; Dipole interactions; ferronematic; Flow characteristics; Heat treatment; Liquid crystals; Locomotion; magnetic actuation; Magnetic fields; Magnetic permeability; Magnets; Mechanical analysis; Nematic crystals; Polydimethylsiloxane; Room temperature; tetramethyldisiloxane structural motif; Three dimensional printing; magnetic actuation; cobalt; liquid crystals; ferronematic; tetramethyldisiloxane structural motif
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202307006

Ferronematics that are generally based on nematic liquid crystals (LCs) doped with magnetic nanoparticles, synergistically taking advantage of the anisotropic and flow characteristics of the nematic host and the magnetic susceptibility of the dopant, have powerful applications as magnetically actuated soft materials. In this work, a Co(II) complex, which alone presents both characteristics, is built with a salen‐type ligand 3,5‐dichlorosubstituted at the aromatic nuclei and has a tetramethyldisiloxane spacer, which makes it one of the few metallomesogens containing this structural motif. Paramagnetic crystals, through heat treatment above 110 °C, change into magnetic nematic LCs. Applying a perpendicular magnetic field of 50 mT, the nematic droplets align two by two through dipole–dipole interactions. By incorporating it into a silicone matrix consisting mainly of polydimethylsiloxane, a 3D printable ink is formulated and crosslinked under various shapes. In this environment, the cobalt complex is stabilized in an LC state at room temperature and, due to its anisotropy, facilitates the mechanical response to magnetic stimuli. The resulting objects can be easily manipulated on fluid or rough surfaces using external magnetic fields, behave like magnets by themselves, and show reversible locomotion. A Co(II) complex with a salen‐type ligand containing a tetramethyldisiloxane spacer can self‐assemble into nematic droplets and exhibit a magnetic‐stimuli response upon transitioning from a solid to a liquid crystal state. By incorporating this compound into a polydimethylsiloxane matrix, new magnetic‐driven materials are successfully developed.