Stimuli-Responsive Self-Assembly of π-Conjugated Liquids Triggers Circularly Polarized Luminescence

Abstract

We developed novel room-temperature stimuli-responsive N-heteroacene-based liquid materials bearing a chiral alkyl chain. When these liquid materials were exposed to HCl vapor as an external stimulus, a disordered–ordered state change occurred immediately to yield self-assembled solid states from fluidic liquids. The self-assembly mechanism during this state change was evaluated by experimental in situ observations and molecular dynamics simulations over various spatiotemporal scales. These self-assembled structures led to supramolecular chirality through the influence of the chiral alkyl chain. As a result, circularly polarized luminescence (CPL) was triggered in the solid state, which was absent in the precursor liquid, thereby rendering this the first report on a stimuli-responsive CPL on/off liquid material. In addition, the initial state was recovered by exposure to air or upon heating. Moreover, the synergy between the experimental and the theoretical studies opens a new avenue to develop a novel class of stimuli-responsive materials and to discover novel phenomena in such materials.

Liquid Structures and Diffusion Dynamics of Alkyl–Pyrene Liquids Studied by Molecular Dynamics Simulations

“…Similarly, compound 3 , which forms a pairing π–π stacking structure, diffuses slower than compound 4 whose π-core is in an isolated environment. In previous studies of other alkyl−π liquids, the phase transition to an ordered phase was observed in which the multilayer π–π stacking grows in chemical stimuli response and a viscosity increase was observed. , Our mechanism can provide a consistent explanation for this as well.…”

“…However, atomistic models of the alkyl−π liquids without coarse graining are also necessary to understand the molecular mechanism of the rheology control by changing the substituent positions. Previous theoretical studies based on MD simulations for 1 μs in total showed that the chemical-stimulated phase transition of alkyl−π liquids to an ordered phase where the experimentally measured viscosity significantly increases is attributed to the formation of multilayer π–π stacking columnar structures. , However, the MD analyses were limited to an initial process of the ordered structure formation and static properties of the liquid structures due to short trajectory lengths. We therefore carried out long-time MD simulations for tens of microseconds in total with atomic molecular models and succeeded in semiquantitatively reproducing the rheological properties experimentally observed (Table ).…”

“…Here, we present a theoretical study on the rheological properties of the alkyl–pyrene liquids, compounds 1 – 4 , by means of atomistic molecular dynamics (MD) simulations. MD simulations have been utilized to investigate the rheological properties of liquids such as viscosity coefficients through analyses of microscopic dynamics and diffusion processes of molecules in liquids underlying the rheological properties for various molecular fluids including hydrocarbons, − ionic liquids, , and deep eutectic solvents. − For the bulk alkyl−π systems, the initial processes of order–disorder phase transition were investigated by MD simulations for 1 μs in total, and their static liquid structures and optoelectronic properties were analyzed. , …”

Stimuli-responsive helical polymeric particles with amplified circularly polarized luminescence

“…Due to their remarkable potential applications in changeable photoemission sensors, 3D optical displays, CPL dynamic switching, optical amplifiers, data storage, multiple encryption and anti-counterfeiting, stimuli-responsive circularly polarized luminescent (CPL) materials are attracting widespread attention. [1][2][3][4][5] Currently, a number of stimuli-responsive CPL materials with a high luminescence dissymmetry factor (g lum ) have been favored and fabricated via approaches utilizing the dynamic assembly of liquids, 6 light emitting molecule-binding chiral centers, 7 metal-induced complexes, 8 energy level-assisted photonic inversion, 9 anion-triggered switching, 10 etc. Nevertheless, the fabrication of stimuli-responsive CPL materials with changeable |g lum | and flexible design in the solid state remains a great challenge because of the disorder and aggregation-caused quenching (ACQ) of solid aggregates.…”

Two Cholesterol-Containing Pyrene Derivatives: Subtle Spacer Difference, Diverse Stimuli-Responsive Luminescence, Chirality, and Self-Assembly Behaviors

“…To realize it, one of the most effective methods is doping chiral luminogens into achiral nematic liquid crystals (N-LCs). − Besides g lum , another important parameter of CPL is the polarization direction (left-handed and right-handed). Inversion of CPL signals was usually realized by changing the molecular structure or chirality of chiral dopants. − It would be more convenient to inverse the CPL signals of N*-LC by simply adjusting the doping ratio of chiral dopants; however, related LC systems were rarely reported.…”