Nanosegregated Chiral Materials with Self‐Assembled Hierarchical Mesophases: Effect of Thermotropic and Photoinduced Polymorphism in Rodlike Molecules

Abstract

Supramolecular chirality in a binary mixture of achiral bent-core (BC) and achiral rodlike mesogens was observed. Three different nanosegregated mesophases were determined in the binary system, and meaningful changes in circular dichroism (CD) were detected near the phase-transition temperatures of the rodlike mesogens. The highest CD intensity in the binary system was noted in the nanosegregated mesophase, in which the BC mesogens were in the helical nanofilament (HNF) phase and the rodlike mesogens were in the smectic A phase. The supramolecular chirality in the binary mixture was attributed to the self-assembled hierarchical chiral superstructures. Based on the experimental results, plausible scenarios for the chiral superstructures of the rodlike molecules embedded in the HNF networks are suggested. In addition, a system comprising BC and rodlike molecules doped with a photoresponsive compound exhibited remarkable photoswitching of CD intensity. According to the isothermal photoinduced phase transition of the embedded molecules in BC molecular HNFs, the observed CD intensities can be dynamically and reversibly modulated. Such a material with easily controllable functionality is of considerable interest in the field of materials science.

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 . In addition, a giant circular dichroism (CD) signal was observed at a specific mesophase . Such a giant CD signal could have resulted from a chiral aggregate of achiral liquid crystalline rod‐like molecules embedded in a network of HNFs formed by bent‐core molecules …”

“…In addition, a giant circular dichroism (CD) signal was observed at a specific mesophase . Such a giant CD signal could have resulted from a chiral aggregate of achiral liquid crystalline rod‐like molecules embedded in a network of HNFs formed by bent‐core molecules …”

Photomodulating chiroptic behaviors in nanosegregated mesophase from a mixture system consisting of nonchiral bent-core and photo-responsive rod-like mesogens

“…A mixed system consisting of nonchiral BC and rodlike mesogens has been reported as a novel chiroptic material [8][9][10][11][12][13][14]. Especially, mixed systems consisting of nonchiral BC and photoresponsive (PR) rod-like mesogens are promising as photomodulating chiroptical switching materials [13,14]. Kim et al reported the first example of a mixture of nonchiral BC molecules and PR LC molecules possessing a nematic (N) phase [13].…”

“…The authors posited that this reversible chiroptical modulation could be used for rewritable optical storage, among other applications. More recently, Jeon et al prepared another mixture system consisting of nonchiral BC and PR mesogens, which was different from the molecule system that was used by Kim et al [14]. In this case, the authors reported the existence of a nanosegregated < HNF/SmA > phase.…”