Quest for a Rational Molecular Design of Alkyl‐Distyrylbenzene Liquid by Substitution Pattern Modulation**

Abstract

Alkyl-π functional molecular liquids (FMLs) are of interest for fabricating soft electronic devices due to their fluidic nature and innate optoelectronic functions from the πconjugated moiety. However, predictable development of alkyl-π FMLs with the desired liquid and optoelectronic properties is challenging. A series of alkyl-distyrylbenzene (DSB) liquids was studied in terms of the substituent position effect by attaching 2-octyldodecyl chains at (2,4-), (2,5-), (2,6-), and (3,5-). The effect of the alkyl chain length was investigated by attaching 2-hexyldecyl, 2-decyltetradecyl (C 10 C 14 ), and 2-dodecylhexadecyl at the (2,5-) substituent position. The 2,5-C 10 C 14 substituent pattern constructed a superior alkyl-DSB liquid with a lower viscosity, intrinsic optical properties, and high thermal-and photo-stabilities. The discovered 2,5-C 10 C 14 was applied to dicyanostyrylbenzene and comparable liquid physical and optical superiorities were confirmed. This molecular design is useful for creating alkyl-π FMLs with the aforementioned advantages, which are applicable for deformable and flowable optoelectronic devices.

Room‐Temperature Alkyl‐Diphenylpyrene Liquefication by Molecular Desymmetrization

“…Solid‐state NMR provides qualitative insight into this assumption ( Figure 7). [11,16,26] In the dipole decoupling magic‐angle spinning (DD‐MAS) 13 C‐NMR spectrum of 1b fresh melt, relatively sharp alkyl and broad aromatic signals were observed. The signals at the inner alkyl chains (C α : ca .…”

“…Solid-state NMR provides qualitative insight into this assumption (Figure 7). [11,16,26] In the dipole decoupling magic-angle spinning (DD-MAS) 13 Accordingly, it can be said that the outer part of the alkyl chains has fast molecular motion and is well averaged, as seen in routine solution NMR. On the other hand, the aromatic part and the nearby inner alkyl part have considerably slow molecular motion even in the liquid state.…”

“…For example, tetra‐alkylated diphenylanthracene, previously reported as a liquid, was later shown to be a supercooled liquid [10] . We recently studied the effect of the alkoxyl substituent position on the liquid phase stability of tetra‐alkylated distyrylbenzenes [11] . Although some isomers appear to be liquids in the as‐synthesized state, careful examination reveals that they crystallize at above 25 °C.…”

Responsive molecular liquid materials

“…liquids. [51,53,137,138] The molecular structure and stability of the supercooled state have been studied in detail utilizing a series of anthracenes with branched alkyl chains as model molecules. [137] If the alkyl chain is too short relative to the size of the π-conjugated unit, the compound becomes solid at room temperature because the π-π interactions are not sufficiently hindered.…”

“…[52] A remarkable point in such a molecular design is that the fluidity in a solvent-free liquid state and the strength of the interaction between functional cores can be controlled by the length, the degree of branching, and the substitution position of the flexible molecular chains. [53][54][55][56][57][58][59] For example, in a study using alkylated liquid pyrenes as the model molecule, [60] when only one side of the pyrene core was modified with alkyl chains so that the pyrene core was not fully covered, the luminescence was delivered from the excimer formation between the pyrene cores. In this case, van der Waals and π-π interactions acted between the molecules (Figure 1a).…”