Photomodulated Supramolecular Chirality in Achiral Photoresponsive Rodlike Compounds Nanosegregated from the Helical Nanofilaments of Achiral Bent-Core Molecules

Abstract

We prepared a nonchiral mixture of achiral bent-core molecules and photoresponsive rodlike liquid crystalline (LC) molecules. With the help of the isothermal photochemical nematic (N)-isotropic (Iso) phase transition of the photoresponsive rodlike LC molecules, the corresponding phase transition from a dark conglomerate BX phase to another distinguishable dark conglomerate B4 phase took place in the mixture. A large circular dichroism (CD) signal originating from supramolecular chirality was detected in the initial BX phase. On the other hand, the detected CD signal was decreased in the B4 phase after UV irradiation. Interestingly, the decreased CD signal could be reverted to the initial CD signal with visible irradiation. This chiroptical process revealed in this work was stable and reversible and thus opens up the possibility of practical applications such as rewritable optical storage.

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

“…Based on the temperature dependence of transmittance (Figure 1a)a nd the XRD results( Figure 1c), three nanosegregated phases, < HNF/SmA > , < HNF/N > ,a nd < HNF/Iso > ,w ere identified with increasingt emperature in the binary mixture. [3,[9][10][11][12][13][14] CD observations maximum CD peak intensity of the positive domain l % 300 nm as af unctiono ft emperature in the two abovementioned mixtures (M1 and M2). Phase diagrams of mixtures with differentP 8-O-PIMBa nd 8CB contentsa re shown in Figure S1 in the Supporting Information.…”

“…As shown in Figure 4a,t he diffraction intensity at 2q = 2.038 from the HNFs of P8-O-PIMB barely changed upon UV irradiation. [12] Conclusion Three different nanosegregated phases (< HNF/SmA > , < HNF/ SmA > ,a nd < HNF/Iso >)w ere observed with increasing temperaturei nb inary mixtures of achiral BC molecules (P8-O-PIMB) and achiral rodlike mesogens (8CB). The diffraction intensity could be restored by visible-light irradiation (light-emitting diode; l = 450 nm, 30 mW cm À2 )b ecause the trans isomer of the doped azobenzene molecule stabilized the SmA phase of 8CB, whereas the cis isomer disturbed the SmA phase.…”

“…In addition, ap hotoresponsive ternary mixture (M3) constituting P8-O-PIMB, 8CB, and an azobenzene compound (BMAB), [12,19] was prepared. Twob inary mixtures were prepared:M 1a nd M2.…”

“…[2][3][4][5][6][7][8] Herein, we explore an interesting chirality-related phenomenon in ab inary mixture of achiral bent-core (BC) mesogensa nd rodlikem esogens.P eculiar chiral phenomena in achiral BC mesophases have attracted significant research interest since the discovery of spontaneous chiral resolution in achiral BC molecular systems. [3,11,12] Amongs everal banana phases,t he helical nanofilament( HNF) B4 phase has attracted particulari nterestb ecause of its unique chiral superstructure,i nw hich twisted nanofilaments form through the self-assembly of achiral molecules. [3,11,12] Amongs everal banana phases,t he helical nanofilament( HNF) B4 phase has attracted particulari nterestb ecause of its unique chiral superstructure,i nw hich twisted nanofilaments form through the self-assembly of achiral molecules.…”

“…[9,10] The mesophases found in BC molecular systems, termed "bananap hases," are different from the conventionalp hases foundi nr odlikem esogens. [3,11,12] Amongs everal banana phases,t he helical nanofilament( HNF) B4 phase has attracted particulari nterestb ecause of its unique chiral superstructure,i nw hich twisted nanofilaments form through the self-assembly of achiral molecules. [3] Ta kanishi et al observed the direct isotropic (Iso)-B4 phase transition and found that the chiral segregated B4 phase was stabilized when BC molecules( 1,3-phenylene bis[4-(4-octyloxyphenyliminomethyl)benzoate]( P8-O-PIMB)) were mixed with rodlikem olecules (4'-pentyl-4-biphenylcarbonitrile (5CB)).…”