Dynamic heterogeneity of a nanostructure in the hyper-swollen B4 phase of achiral bent-core molecules diluted with rod-like liquid crystals

Abstract

We studied the dynamics in the chiral mesogenic phases observed in binary mixtures of 5CB and bent-core molecules by using dynamic light scattering. In the lower-temperature phase, a clear orientational fluctuation was observed, which was not observed in the higher-temperature one. The wave number dependence of the relaxation frequency strongly indicates that nanoscale phase separation occurs and that the fluctuations of 5CB with nematic order are suppressed by the bent-core–rich domains. The spatial heterogeneity of the nematic dynamic motion yields exact information on the characteristic size of the nanostructure, which cannot be obtained by static structural analysis.

Distinctive Thermal Behavior and Nanoscale Phase Separation in the Heterogeneous Liquid-CrystalB4Matrix of Bent-Core Molecules

“…The fact that the discrete anomalies are observed for both the B 2 -B 4 and I-B 4 transitions indicates that the exothermic peaks arise from an intrinsic property of B 4 regardless of the type of higher temperature phases (B 2 and I). The sequential exothermic peaks of the pure B 4 phase still remains in mixtures and leads to a speculation that the B 4 structure of pure P8 can grow independently without being mixed with rodlike 237802-2 molecules, i.e., we expect a phase-separated structure in mixtures, which is in quite good agreement with recent reports [10,11].…”

“…They also mentioned that the HNF structure is very rigid once formed. This novel phase separation in nanoconfined space, which has been difficult to confirm by usual polarized optical microscopy study [7], is supported by dynamic light scattering [11] and precise circular dichroism [12] measurements. Such a complicated morphology rather than having a simple structure due to mixing incompatible components is of general interest in soft materials because it is quite suitable to investigate the effect of the individual molecular dynamics.…”

Chiral Superstructure Mesophases of Achiral Bent‐Shaped Molecules – Hierarchical Chirality Amplification and Physical Properties

“…Namely, they were prealigned and formed a thin film of 2.4 nm thick around the HNFs due to the short‐range interaction between them and the HNF surfaces. Regarding the <B4/N> phase, using dynamic light‐scattering, and then small‐ and wide‐angle X‐ray microbeam and macrobeam scatterings, Takanishi and co‐workers estimated the structure of the <B4/N> phase; 5CB‐rich domains with sizes of 450–600 nm are separated by HNFs consisting of 5–7 smectic layers, with thickness of about 300 Å. The obtained structure is in good accordance with the FFTEM observation, and the model suggested by CD measurements in the mixture of P‐8‐OPIMB and 5CB (Figure d), i.e., the nematic director aligns almost parallel to the grooves of the HNFs.…”

Circularly Polarized Luminescence Induced by Chiral Super Nanospaces

“…Recently, several attempts have been made to construct chiroptical soft materials using mixed systems of achiral bent‐core and rod‐like mesogenic molecules . Various physical measurements, such as freeze‐fractured transmittance electron micrography, small‐angle X‐ray diffraction, differential scanning calorimetry (DSC), and light scattering, have suggested the occurrence of nanoscale phase segregation in these mixed systems. That is, most of the rod‐like molecules are not located within the HNFs formed by the bent‐core molecules but exist outside the HNFs .…”