Liquid Crystalline Tactoidal Microphases in Ferrofluids: Spatial Positioning and Orientation by Magnetic Field Gradients

Abstract

Macroscopic manipulation of self-assembly in lyotropic systems, such as chiral nematic liquid crystals formed by cellulose nanocrystals, is kinetically hindered by the similarity between isotropic and anisotropic phases in composition and physical properties. By creating a significant difference in volumetric magnetic susceptibility between discrete liquid crystalline tactoids and continuous isotropic phases (based on the exclusion effects of tactoids on superparamagnetic doping nanoparticles), we achieved position and orientation control of liquid crystalline tactoids by magnetic field gradients as weak as several hundred gauss per centimeter, where the movement of tactoids is determined by competition between magnetic and gravitational acceleration fields. We also undertook a preliminary examination of the trapping of a liquid crystalline phase in the potential well of a quadrupole magnetic field. This method enabled us to control the phase separation rate and configuration, as well as the orientation of director fields in both tactoids and macroscopic ordered phases.

Elastic constants of biological filamentous colloids: estimation and implications on nematic and cholesteric tactoid morphologies

“…Due to the very sensitive conditions, experimental measurements of the elastic constants remain nontrivial and time consuming. Moreover, water-based biological CLC such as cellulose nanocrystals (CNC) and amyloid fibrils are weakly sensitive to electric and magnetic fields, and the measurement of the elastic constant for these systems is extremely elusive [43][44][45] .…”

Methylcellulose–Cellulose Nanocrystal Composites for Optomechanically Tunable Hydrogels and Fibers

“…Consequently, a range of fully cellulose-derived advanced and functional materials and (nano)composites can be prepared by selecting the correct raw materials and their combinations [ 2 , 3 , 4 , 5 , 6 ]. Furthermore, the inherent relative ease of modifiability makes cellulose applicable in a wide range of conditions and enables synergies with other materials, such as carbon nanotubes, graphene, other biomolecules, and metallic nanoparticles [ 7 , 8 , 9 , 10 , 11 , 12 ]. Potential applications for advanced cellulosic materials include: biomedicine, tissue engineering, photonics, smart materials, emulsions, foaming, and sensors [ 13 , 14 , 15 , 16 , 17 ].…”

Homeotropic Concentric Helix Orientations in Chiral Nematic Cellulose Nanocrystal Films by Local Magnetic Fields

“…[ 41 ] MacLachlan and coworkers demonstrated that gradient magnetic field in ferrofluids provided an effective means to control the position and orientation of liquid crystalline tactoids of CNCs, which may facilitate the formation of new mesophases. [ 42 ] Zhu and coworkers showed that the addition of a small amount of Fe 3 O 4 ‐coated CNCs into homogeneous CNC suspensions allowed tuning of the helical pitch using ultrasmall magnetic field. [ 43 ] To our knowledge, approaches to control over the self‐assembly to produce left‐handed chiral nematic CNC films with homeotropic concentric helix orientations in the planar textures displaying plane‐lateral chiroptical properties remain unexplored.…”