Kinetics of motile solitons in fluid nematics

Solitary waves, dubbed "solitons", are special types of waves that propagate for an infinite distance under ideal conditions. These waves are ubiquitously found in nature such as typhoon or neuron signals. Yet, their artificial generation and the control of their propagation remain outstanding challenges in materials science owing to an insufficient understanding of the experimental conditions and theoretical aspects. Herein, a generic strategy for forming particle-like solitons and controlling their kinetics in nematic fluid media is reported. The key to the realisation of the generation of solitons and the control of their kinetics is the coupling between the fluid elasticity and the background flow flux, as evidenced by experimental observations and theoretical approaches. The findings of this study enable the exploration of solitons in a wide range of materials and have technological ramifications for the lossless transport of energy or structures.Comment: Manuscript 25 pages, 6 figures, Supplementary Information 23 pages, 13 figure

Spherical-cap droplets of a photo-responsive bent liquid crystal dimer

The stays and research activities of J. Y. and F. A. in Hungary, and P. S. and A. B. in Japan are supported by the JSPS-HAS bilateral program. J. Y. was partially supported by JSPS KAKENHI Grant Number 15K17739. A. J. acknowledges financial support by NSF DMR: 1307674. Financial support from the grants NKFIH PD 121019 and FK 125134 are acknowledged.Peer reviewedPostprin

A supramolecular helix that disregards chirality

The functions of complex crystalline systems derived from supramolecular biological and non-biological assemblies typically emerge from homochiral programmed primary structures via first principles involving secondary, tertiary and quaternary structures. In contrast, heterochiral and racemic compounds yield disordered crystals, amorphous solids or liquids. Here, we report the self-assembly of perylene bisimide derivatives in a supramolecular helix that in turn self-organizes in columnar hexagonal crystalline domains regardless of the enantiomeric purity of the perylene bisimide. We show that both homochiral and racemic perylene bisimide compounds, including a mixture of 21 diastereomers that cannot be deracemized at the molecular level, self-organize to form single-handed helical assemblies with identical single-crystal-like order. We propose that this high crystalline order is generated via a cogwheel mechanism that disregards the chirality of the self-assembling building blocks. We anticipate that this mechanism will facilitate access to previously inaccessible complex crystalline systems from racemic and homochiral building blocks

Magneto-chiral nonlinear optical effect with large anisotropic response in two-dimensional halide perovskite

The chiral organic-inorganic halide perovskites (OIHPs) are vital candidates for superior nonlinear optical (NLO) effects associated with circularly polarized (CP) light. NLO in chiral materials often couples with magnetic dipole (MD) transition, as well as the conventional electric dipole (ED) transition. However, the importance of MD in NLO process of chiral OIHPs has not yet been well recognized. Here, the analysis of second harmonic generation circular dichroism (SHG-CD) provides the direct evidence that the MD contribution leads to a large anisotropic response to CP lights in chiral OIHPs, (R-/S-MBACl)2PbI4. The thin films exhibit great sensitivity to CP lights over a wide wavelength range, and the g-value reaches up to 1.57 at the wavelength where the contribution of MD is maximized. Furthermore, it is also effective as CP light generator, outputting CP-SHG with maximum g-factor of 1.76 upon the stimulation of linearly polarized light. This study deepens the understanding of the magneto-optical NLO processes in chiral systems

Rapid, solvent-minimized and sustainable access to various types of ferroelectric-fluid molecules by harnessing mechano-chemical technology

Recently, ferroelectric fluid, such as ferroelectric nematic liquid crystals (NFLCs) and ferroelectric smectic A LCs (SmAFLCs), has been of great fundamental and practical interest owing to its excellent polarization properties (e.g., dielectric permittivity, polarization, and nonlinear optical coefficient). To deeply understand the physical underpinning of such emergent ferroelectric phases and develop state-of-the-art device applications, effective preparation of various NF molecules is essential. Herein, to expand the NFLC molecular library, we implemented a mechanochemical (MC) technique for the production of LCs, demonstrating its high synthetic compatibility with NF/SmAFLCs. Chemical building blocks with high polarity can be bonded one by one through various ball-milling MC reactions, resulting in rapid access to NFLC molecules, a series of DIO, RM734, UUZU, and BIOTN, with high yield within 2.7–7 h for 4–8 steps. For a new DIO variant, in which a terminal alkyl chain was completely removed, for the first time, we discovered the direct phase transition from the isotropic liquid from the SmAF phase. Furthermore, the highly bistable polarization memory (~5.2 μC cm−2) in the SmAF phases was evaluated using the positive–up–negative–down (PUND) method

Reconfigurable Large-Scale Pattern Formation Driven by Topological Defect Separation in Liquid Crystals

Large-scale patterning of topological defects is vital and challenging from both fundamental and technological points of view in anisotropic fluids. However, this is usually difficult because of their unfavorably high-energy states. Here, a simple but general pathway for topology engineering is presented: processing topological defects and shape large-scale patterns in materials with liquid crystalline nature. Dragging field is created through flowing materials at liquid–liquid crystal phase transition temperature or designing electric-field driven temperature gradient. The dragging fields coupled to a dense colony of topological defects with random spatial distribution, they form nontrivial periodic ordered topological patterns that are energetically unfavorable compared to the uniform ground state but are stable in the stationary state. Topological polymeric films based on the strategy are also fabricated. The dragging speed and surface interactions are found to be dominant factors in generating and stabilizing the patterns. This strategy endows fluids with regular and large-scale topological patterns, paving a new way for the development of fluids and gels with spatially modulated topological nature