Airflow-aligned helical nanofilament (B4) phase in topographic confinement

Abstract

We investigated a controlled helical nanofilament (HNF: B4) phase under topographic confinement with airflow that can induce a shear force and temperature gradient on the sample. The resulting orientation and ordering of the B4 phase in this combinational effort was directly investigated using microscopy. The structural freedom of the complex B7 phase, which is a higher temperature phase than the B4 phase, can result in relatively complex microscopic arrangements of HNFs compared with the B4 phase generated from the simple layer structure of the B2 phase. This interesting chiral/polar nanofilament behaviour offers new opportunities for further exploration of the exotic physical properties of the B4 phase.

Missing Link between Helical Nano‐ and Microfilaments in B4 Phase Bent‐Core Liquid Crystals, and Deciphering which Chiral Center Controls the Filament Handedness

“…In addition, we also obtained tapping mode AFM images ( Figure ). With the sample of ( m R , p S )‐ 5 cooled at a rate of 5 °C min −1 from the isotropic liquid phase to room temperature (≈20 °C), the HNFs with average width and helical pitch matching the values obtained by SEM image analysis (≈100 nm width and ≈350 nm helical pitch) these AFM images also confirm the left‐handedness for ( m R , p S )‐ 5 .…”

An unusual type of polymorphism in a liquid crystal

“…The helical pitch is also much larger (about fivefold) for the HμF phase of the rapidly cooled compound 1 than for previously reported HNF phases (about ~900 nm–1 μm vs. the typically reported value of ~200 nm). The diameter and pitch of the filaments are in fact in between the HNF (B4) phase and the telephone wire (and often corkscrew) structure of the B7 phase of bent-core materials 22 , which have modulated smectic layer structure 23 , 24 . On the contrary, images of the slow-cooled sample do not show discrete filaments (Fig.…”

Circularly polarized luminescence in chiral orientationally ordered soft matter systems

“…[191] At least eight different smectic phases made of bent-core molecules have been found, which are named as B1-B8 phases, [192] where "B" stands for "bowshaped," "bent-core," "bent-shaped," or "banana-shaped." [193] The B4 phase or HNFs [55,[185][186][187][188][189]194] of bent-core compounds was first resolved with freeze-fracture transmission electron microscopy by Clark in 2009. [119] Figure 7a illustrates the mechanism of the formation of HNFs.…”

“…The chirality and spontaneous polar order break the symmetry, coupling to drive the layer to undergo the saddle‐splay deformation, [184] forming a spectacular hierarchical structure of the twisted layers [119] . Since the chiral resolution and the polar switching were discovered in bent‐core LCs, several studies have investigated new LCs comprising bent‐core molecules and their unique phase behaviors, orientational control of HNF growth, [185‐190] and excellent gelation ability [191] . At least eight different smectic phases made of bent‐core molecules have been found, which are named as B1–B8 phases, [192] where “B” stands for “bow‐shaped,” “bent‐core,” “bent‐shaped,” or “banana‐shaped.” [193] The B4 phase or HNFs [55,185‐189,194] of bent‐core compounds was first resolved with freeze‐fracture transmission electron microscopy by Clark in 2009 [119] .…”