Mesomorphic Organization and Thermochromic Luminescence of Dicyanodistyrylbenzene‐Based Phasmidic Molecular Disks: Uniaxially Aligned Hexagonal Columnar Liquid Crystals at Room Temperature with Enhanced Fluorescence Emission and Semiconductivity

Abstract

A new dicyanodistyrylbenzene‐based phasmidic molecule, (2Z,2′Z)‐2,2′‐(1,4‐phenylene)bis(3‐(3,4,5‐tris(dodecyloxy)phenyl)acrylonitrile), GDCS, is reported, which forms a hexagonal columnar liquid crystal (LC) phase at room temperature (RT). GDCS molecules self‐assemble into supramolecular disks consisting of a pair of molecules in a side‐by‐side disposition assisted by secondary bonding interactions of the lateral polar cyano group, which, in turn, constitute the hexagonal columnar LC structure. GDCS shows very intense green/yellow fluorescence in liquid/solid crystalline states, respectively, in contrast to the total absence of fluorescence emission in the isotropic melt state according to the characteristic aggregation‐induced enhanced emission (AIEE) behavior. The AIEE and two‐color luminescence thermochromism of GDCS are attributed to the peculiar intra‐ and intermolecular interactions of dipolar cyanostilbene units. It was found that the intramolecular planarization and restricted molecular motion associated with a specific stacking situation in the liquid/solid crystalline phases are responsible for the AIEE phenomenon. The origin of the two‐color luminescence was elucidated to be due to the interdisk stacking alteration in a given column driven by the specific local dipole coupling between molecular disks. These stacking changes, in turn, resulted in the different degree of excited‐state dimeric coupling to give different emission colors. To understand the complicated photophysical properties of GDCS, temperature‐dependent steady‐state and time‐resolved PL measurements have been comprehensively carried out. Uniaxially aligned and highly fluorescent LC and crystalline microwires of GDCS are fabricated by using the micromolding in capillaries (MIMIC) method. Significantly enhanced electrical conductivity (0.8 × 10−5 S•cm−1/3.9 × 10−5 S•cm−1) of the aligned LC/crystal microwires were obtained over that of multi‐domain LC sample, because of the almost perfect shear alignment of the LC material achieved in the MIMIC mold.

Visible Thermochromism in Vanadium Pentoxide Coatings

“…Organic thermochromic compounds include the following: Conjugated polymers 21 − Thermochromism arises due to the conformational change, which influences the effective conjugation length of the polymer backbone. A slight change in the structure usually leads to a significant color shift.…”

A Solution‐Processable Liquid‐Crystalline Semiconductor for Low‐Temperature‐Annealed Air‐Stable N‐Channel Field‐Effect Transistors

“…232-233 8C), [32] which indicates that two opposing structural effects are mostly balanced between the two semiconductors:t he steric bulk of the flexible alkyl substituents (2-octyldodecyl > n-dodecyl) and the p rigidity/co-planarity of the molecular backbone( Figure S5;d ihedral angle (q Ph-Th ) = 22 (a,w-2OD-TIFDMT)v s. 488 (b-DD-TIFDMT)). [35] Therefore, the endothermicp eak at 139 8Cw ith an enthalpy of 10.06 Jg À1 was assigned to ac rystal-to-mesophase transition. These observed DSC characteristics are indicative of at ypical liquid-crystalline (LC) material, [33,34] and the a,w-2OD-TIFDMT powder wasf urther examined by using ap olarizedo pticalm icroscope (POM) to observe the formation of mesomorphic features as af unction of temperature.T he typical pseudof ocal-conic fan-shaped texture of ah exagonal columnar (Col h )l iquid crystal phase was observed in the second heatingc ycle when the temperature was raised above 139 8C ( Figure 3d).…”

Cyanostilbene bent-core molecules: a route to functional materials

“…,40,41 thus allowing applications in biological imaging,42,43 optical storage,[44][45][46][47][48][49][50] optoelectronic devices (OLEDs, OFETs, solar cells), 51-55 promising a new generation of multifunctional materials. The excellent characteristics of the cyanostilbene chromophore can be combined with those of liquid crystals 44,49,[56][57][58][59][60][61][62][63][64][65]. In particular, this combination of properties remains unexplored with BCLCs.…”